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  • 1.
    Afzal, Muhammad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Wang, Baoyuan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Xia, Chen
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Zhang, Wei
    He, Yunjuan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Jayasuriya, Jeevan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Zhu, Binzhu
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier2016Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, s. 136-142Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is synthesized via a chemical co-precipitation technique for a low temperature solid oxide fuel cell (LTSOFC) (300-600 degrees C) and electrolyte-layer free fuel cell (EFFC) in a comprehensive study. The EFFC with a homogeneous mixture of samarium doped ceria (SDC): BSCF (60%:40% by weight) which is rather similar to the cathode (SDC: BSCF in 50%:50% by weight) used for a three layer SOFC demonstrates peak power densities up to 655 mW/cm(2), while a three layer (anode/ electrolyte/cathode) SOFC has reached only 425 mW/cm(2) at 550 degrees C. Chemical phase, crystal structure and morphology of the as-prepared sample are characterized by X-ray diffraction and field emission scanning electron microscopy coupled with energy dispersive spectroscopy. The electrochemical performances of 3-layer SOFC and EFFC are studied by electrochemical impedance spectroscopy (EIS). As-prepared BSCF has exhibited a maximum conductivity above 300 S/cm at 550 degrees C. High performance of the EFFC device corresponds to a balanced combination between ionic and electronic (holes) conduction characteristic. The Schottky barrier prevents the EFFC from the electronic short circuiting problem which also enhances power output. The results provide a new way to produce highly effective cathode materials for LTSOFC and semiconductor designs for EFFC functions using a semiconducting-ionic material.

  • 2.
    Ahlquist, Mårten
    et al.
    Lund University.
    Gustafsson, Mikaela
    Karlsson, Magnus
    Thaning, Mikkel
    Axelsson, Oskar
    Wendt, Ola F.
    Rhodium(I) hydrogenation in water: Kinetic studies and the detection of an intermediate using C-13{H-1} PHIPNMR spectroscopy2007Inngår i: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 360, nr 5, s. 1621-1627Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism for hydrogenation of dimethylmaleate in water using cationic rhodium complexes with water-soluble bi-dentate phosphines has been investigated using kinetics and a novel method for the indirect detection of intermediates in catalytic hydrogenation reactions, whereby a late intermediate was detected. A mechanism is proposed involving fast, irreversible substrate binding followed by a rate-determining reaction with dihydrogen.

  • 3.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Ramachandran, P.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngard, J.
    Bokkers, A.
    Liquid-gas flow patterns in a narrow electrochemical channel2011Inngår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 66, nr 10, s. 2252-2260Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The flow in a narrow (3 mm wide) vertical gap of an electrochemical cell with gas evolution at one electrode is modeled by means of the two-phase Euler-Euler model. The results indicate that at certain conditions an unsteady type of flow with vortices and recirculation regions can occur. Such flow pattern has been observed experimentally, but not reported in previous modeling studies. Further analysis establishes that the presence of a sufficient amount of small (similar to 10 mu m) bubbles is the main factor causing this type of flow at high current densities.

  • 4.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M P
    Ramachandran, P
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngard, J
    Bokkers, A
    On the electrode boundary conditions in the simulation of two phase flow in electrochemical cells2011Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, nr 14, s. 8557-8559Artikkel i tidsskrift (Fagfellevurdert)
  • 5.
    Andersson, Joakim
    KTH, Skolan för kemivetenskap (CHE).
    Lifetime estimation of lithium-ion batteries for stationary energy storage system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the continuing transition to renewable inherently intermittent energy sources like solar- and wind power, electrical energy storage will become progressively more important to manage energy production and demand. A key technology in this area is Li-ion batteries. To operate these batteries efficiently, there is a need for monitoring of the current battery state, including parameters such as state of charge and state of health, to ensure that adequate safety and performance is maintained. Furthermore, such monitoring is a step towards the possibility of the optimization of battery usage such as to maximize battery lifetime and/or return on investment. Unfortunately, possible online measurements during actual operation of a lithium-ion battery are typically limited to current, voltage and possibly temperature, meaning that direct measurement of battery status is not feasible. To overcome this, battery modeling and various regression methods may be used. Several of the most common regression algorithms suggested for estimation of battery state of charge and state of health are based on Kalman filtering. While these methods have shown great promise, there currently exist no thorough analysis of the impact of so-called filter tuning on the effectiveness of these algorithms in Li-ion battery monitoring applications, particularly for state of health estimation. In addition, the effects of only adjusting the cell capacity model parameter for aging effects, a relatively common approach in the literature, on overall state of health estimation accuracy is also in need of investigation.

    In this work, two different Kalman filtering methods intended for state of charge estimation: the extended Kalman filter and the extended adaptive Kalman filter, as well as three intended for state of health estimation: the dual extended Kalman filer, the enhanced state vector extended Kalman filer, and the single weight dual extended Kalman filer, are compared from accuracy, performance, filter tuning and practical usability standpoints. All algorithms were used with the same simple one resistor-capacitor equivalent circuit battery model. The Li-ion battery data used for battery model development and simulations of filtering algorithm performance was the “Randomized Battery Usage Data Set” obtained from the NASA Prognostics Center of Excellence. 

    It is found that both state of charge estimators perform similarly in terms of accuracy of state of charge estimation with regards to reference values, easily outperforming the common Coulomb counting approach in terms of precision, robustness and flexibility. The adaptive filter, while computationally more demanding, required less tuning of filter parameters relative to the extended Kalman filter to achieve comparable performance and might therefore be advantageous from a robustness and usability perspective. Amongst the state of health estimators, the enhanced state vector approach was found to be most robust to initialization and was also least taxing computationally. The single weight filter could be made to achieve comparable results with careful, if time consuming, filter tuning. The full dual extended Kalman filter has the advantage of estimating not only the cell capacity but also the internal resistance parameters. This comes at the price of slow performance and time consuming filter tuning, involving 17 parameters. It is however shown that long-term state of health estimation is superior using this approach, likely due to the online adjustment of internal resistance parameters. This allows the dual extended Kalman filter to accurately estimate the SoH over a full test representing more than a full conventional battery lifetime. The viability of only adjusting the capacity in online monitoring approaches therefore appears questionable. Overall the importance of filter tuning is found to be substantial, especially for cases of very uncertain starting battery states and characteristics.

  • 6. Armstronga, D. A.
    et al.
    Huie, R. E.
    Lymar, S.
    Koppenol, W. H.
    Merényi, Gabor
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Neta, P.
    Stanbury, D. M.
    Steenken, S.
    Wardman, P.
    Standard electrode potentials involving radicals in aqueous solution: Inorganic radicals2013Inngår i: BioInorganic Reaction Mechanisms, ISSN 2191-2491, Vol. 9, nr 1-4, s. 59-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inorganic radicals, such as superoxide and hydroxyl, play an important role in biology. Their tendency to oxidize or to reduce other compounds has been studied by pulse radiolysis; electrode potentials can be derived when equilibrium is established with a well-known reference compound. An IUPAC Task Group has evaluated the literature and produced the recommended standard electrode potentials for such couples as (O2/O2 ·-), (HO·, H+/H2O), (O3/O3 ·-), (Cl2/Cl2 ·-), (Br2 ·-/2Br-), (NO2 ·/NO2 -), and (CO3 ·-/CO3 2-). 

  • 7.
    Asplund, Maria
    et al.
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    von Holst, Hans
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Inganäs, Olle
    Composite biomolecule/PEDOT materials for neural electrodes2008Inngår i: Biointerphases, ISSN 1559-4106, Vol. 3, nr 3, s. 83-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrodes intended for neural communication must be designed to meet boththe electrochemical and biological requirements essential for long term functionality. Metallic electrode materials have been found inadequate to meet theserequirements and therefore conducting polymers for neural electrodes have emergedas a field of interest. One clear advantage with polymerelectrodes is the possibility to tailor the material to haveoptimal biomechanical and chemical properties for certain applications. To identifyand evaluate new materials for neural communication electrodes, three chargedbiomolecules, fibrinogen, hyaluronic acid (HA), and heparin are used ascounterions in the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT). The resultingmaterial is evaluated electrochemically and the amount of exposed biomoleculeon the surface is quantified. PEDOT:biomolecule surfaces are also studiedwith static contact angle measurements as well as scanning electronmicroscopy and compared to surfaces of PEDOT electrochemically deposited withsurfactant counterion polystyrene sulphonate (PSS). Electrochemical measurements show that PEDOT:heparinand PEDOT:HA, both have the electrochemical properties required for neuralelectrodes, and PEDOT:heparin also compares well to PEDOT:PSS. PEDOT:fibrinogen isfound less suitable as neural electrode material.

  • 8. Aydin, M.
    et al.
    Durmus, Z.
    Kavas, H.
    Esat, B.
    Sozeri, H.
    Baykal, A.
    Yilmaz, F.
    Toprak, Muhammat S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Synthesis and characterization of poly(3-thiophene acetic acid)/Fe3O4 nanocomposite2011Inngår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 30, nr 6, s. 1120-1126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poly(3-thiophene acetic acid)/Fe3O4 nanocomposite is synthesized by the precipitation of Fe3O4 in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA. and conductivity measurements, respectively. The capping of P3TAA around Fe3O4 nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 +/- 2 nm and 11 +/- 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe3O4 nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.

  • 9.
    Barreiro Fidalgo, Alexandre
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Kumagai, Yuta
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Jonsson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    The role of surface-bound hydroxyl radicals in the reaction between H2O2 and UO22018Inngår i: Journal of coordination chemistry (Print), ISSN 0095-8972, E-ISSN 1029-0389, Vol. 71, nr 11-13, s. 1799-1807Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we have studied the reaction between H2O2 and UO2 with particular focus on the nature of the hydroxyl radical formed as an intermediate. Experiments were performed to study the kinetics of H2O2 consumption and uranium dissolution at different initial H2O2 concentrations. The results show that the consumption rates at a given H2O2 concentration are different depending on the initial H2O2 concentration. This is attributed to an alteration of the reactive interface, likely caused by blocking of surface sites by oxidized U/surface-bound hydroxyl radicals. The dissolution yield given by the amount of dissolved uranium divided by the amount of consumed hydrogen peroxide was used to compare the different cases. For all initial H2O2 concentrations, the dissolution yield increases with reaction time. The final dissolution yield decreases with increasing initial H2O2 concentration. This is expected from the mechanism of catalytic decomposition of H2O2 on oxide surfaces. As the experiments were performed in solutions containing 10mM H2O2 and a strong concentration dependence was observed in the 0.2-2.0mM H2O2 concentration range, we conclude that the intermediate hydroxyl radical is surface bound rather than free.

  • 10.
    Behm, Mårten
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Electrochemical generation of polysulfide liquor and sodium hydroxide from white liquor1998Doktoravhandling, med artikler (Annet vitenskapelig)
  • 11. Benamira, M.
    et al.
    Ringuede, A.
    Albin, V.
    Vannier, R. -N
    Hildebrandt, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cassir, M.
    Gadolinia-doped ceria mixed with alkali carbonates for solid oxide fuel cell applications: I. A thermal, structural and morphological insight2011Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, nr 13, s. 5546-5554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ceria-based composites are developed and considered as potential electrolytes for intermediate solid oxide fuel cell applications (ITSOFC). After giving a survey of the most relevant results in the literature, the structural, thermal and morphological properties of composite materials based on gadolinia-doped ceria (GDC) and alkali carbonates (Li2CO3-K2CO3 or Li2CO3-Na2CO3) are carefully examined. Thermal analyses demonstrate the stability of the composite with very low weight losses of both water and CO2 during thermal cycling and after 168 h ageing. High-temperature and room-temperature X-ray diffraction allowed determining the precise structure of the composite and its regular and reversible evolution with the temperature. The microstructure and morphology of electrolyte pellets, as observed by scanning electron microscopy (SEM), show two-well separated phases: nanocrystals of GDC and a well-distributed carbonate phase. Finally, electrical conductivity determined by impedance spectroscopy is presented as a function of time to highlight the stability of such composites over 1500h.

  • 12.
    Bigum, Lukas
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Hermansson, Anton
    KTH, Skolan för kemivetenskap (CHE).
    Widerberg, Rickard
    KTH, Skolan för kemivetenskap (CHE).
    Syrgasreduktionskatalysatorer i alkaliska elektrolyter2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta projekt handlar om att producera nanopartiklar av kobolt och nickel som kan användas vid katalysering av syrgasreduktionsreaktioner i alkaliska elektrolyter. Idag används ädla metaller som platina (Pt) som katalysator i dessa system men dessa har ett högt pris. Den närmaste konkurrenten som tidigare har utförts försök på är silver.

    I denna rapport så visas att dessa material kan vara komplicerade att syntetisera och separera men att de i slutändan uppvisar en katalytisk effekt och att man med mer tid och ett mer omfattande projekt kan överkomma flera av de problem som redogörs för i denna rapport.

  • 13.
    Björkbacka, Åsa
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Yang, Miao
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Gasparrini, Claudia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Kinetics and mechanisms of reactions between H2O2 and copper and copper oxides2015Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 44, nr 36, s. 16045-16051Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the main challenges for the nuclear power industry today is the disposal of spent nuclear fuel. One of the most developed methods for its long term storage is the Swedish KBS-3 concept where the spent fuel is sealed inside copper canisters and placed 500 meters down in the bedrock. Gamma radiation will penetrate the canisters and be absorbed by groundwater thereby creating oxidative radiolysis products such as hydrogen peroxide (H2O2) and hydroxyl radicals (HO[radical dot]). Both H2O2 and HO[radical dot] are able to initiate corrosion of the copper canisters. In this work the kinetics and mechanism of reactions between the stable radiolysis product, H2O2, and copper and copper oxides were studied. Also the dissolution of copper into solution after reaction with H2O2 was monitored by ICP-OES. The experiments show that both H2O2 and HO[radical dot] are present in the systems with copper and copper oxides. Nevertheless, these species do not appear to influence the dissolution of copper to the same extent as observed in recent studies in irradiated systems. This strongly suggests that aqueous radiolysis can only account for a very minor part of the observed radiation induced corrosion of copper.

  • 14.
    Björnbom, Pehr
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Charge/discharge of an electrochemical supercapacitor electrode pore; non-uniqueness of mathematical models2007Inngår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 9, nr 2, s. 211-215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A thermodynamic analysis has been done to enhance understanding of the relation between various mathematical models for electrochemical supercapacitor pores. For the same capacitive charge/discharge experiment a variety of one-dimensional mathematical model equations concerning the transport of ions and double layer charge/discharge along the pore are shown to be indistinguishable. Some of those indistinguishable equations could be interpreted as derived from diffusional mechanisms while others appear as derived from migrational mechanisms. Ohmic resistivities and diffusivities obtained in such case are not contradicting results but characterize identical physical processes. The results are valid as long as the assumptions of irreversible thermodynamics of local equilibrium along the pore and of linearization of the flux equations hold.

  • 15.
    Boucly, Anthony
    et al.
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France..
    Rochet, Francois
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Arnoux, Quentin
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France..
    Gallet, Jean-Jacques
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Bournel, Fabrice
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Tissot, Heloise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik. Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France.
    Marry, Virginie
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Dubois, Emmanuelle
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Michot, Laurent
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Soft X-ray Heterogeneous Radiolysis of Pyridine in the Presence of Hydrated Strontium-Hydroxyhectorite and its Monitoring by Near-Ambient Pressure Photoelectron Spectroscopy2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 6164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The heterogeneous radiolysis of organic molecules in clays is a matter of considerable interest in astrochemistry and environmental sciences. However, little is known about the effects of highly ionizing soft X-rays. By combining monochromatized synchrotron source irradiation with in situ Near Ambient Pressure X-ray Photoelectron Spectroscopy (in the mbar range), and using the synoptic view encompassing both the gas and condensed phases, we found the water and pyridine pressure conditions under which pyridine is decomposed in the presence of synthetic Sr2+-hydroxyhectorite. The formation of a pyridine/water/Sr2+ complex, detected from the Sr 3d and N 1s core-level binding energies, likely presents a favorable situation for the radiolytic breaking of the O-H bond of water molecules adsorbed in the clay and the subsequent decomposition of the molecule. However, decomposition stops when the pyridine pressure exceeds a critical value. This observation can be related to a change in the nature of the active radical species with the pyridine loading. This highlights the fact that the destruction of the molecule is not entirely determined by the properties of the host material, but also by the inserted organic species. The physical and chemical causes of the present observations are discussed.

  • 16.
    Brown, Shelley
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Diagnosis of the Lifetime Performance Degradation of Lithium-Ion Batteries: Focus on Power-Assist Hybrid Electric Vehicle and Low-Earth-Orbit Satellite Applications2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion batteries are a possible choice for the energy storage system onboard hybrid electric vehicles and low-earth-orbit satellites, but lifetime performance remains an issue. The challenge is to diagnose the effects of ageing and then investigate the dependence of the magnitude of the deterioration on different accelerating factors (e.g. state-of-charge (SOC), depth-of-discharge (DOD) and temperature).

    Lifetime studies were undertaken incorporating different accelerating factors for two different applications: (1) coin cells with a LixNi0.8Co0.15Al0.05O2-based positive electrode were studied with a EUCAR power-assist HEV cycle, and (2) laminated commercial cells with a LixMn2O4-based positive electrode were studied with a low-earth-orbit (LEO) satellite cycle. Cells were disassembled and the electrochemical performance of harvested electrodes measured with two- and three-electrode cells. The LixNi0.8Co0.15Al0.05O2-based electrode impedance results were interpreted with a physically-based three-electrode model incorporating justifiable effects of ageing.

    The performance degradation of the cells with nickelate chemistry was independent of the cycling condition or target SOC, but strongly dependent on the temperature. The positive electrode was identified as the main source of impedance increase, with surface films having a composition that was independent of the target SOC, but with more of the same species present at higher temperatures. Furthermore, impedance results were shown to be highly dependent on both the electrode SOC during the measurement and the pressure applied to the electrode surface. An ageing hypothesis incorporating a resistive layer on the current collector and a local contact resistance (dependent on SOC) between the carbon and active material, both possibly leading to particle isolation, was found to be adequate in fitting the harvested aged electrode impedance data.

    The performance degradation of the cells with manganese chemistry was accelerated by both higher temperatures and larger DODs. The impedance increase was small, manifested in a SOC-dependent increase of the high-frequency semicircle and a noticeable increase of the high-frequency real axis intercept. The positive electrode had a larger decrease in capacity and increase in the magnitude of the high-frequency semi-circle (particularly at high intercalated lithium-ion concentrations) in comparison with the negative electrode. This SOC-dependent change was associated with cells cycled for either extended periods of time or at higher temperatures with a large DOD. An observed change of the cycling behaviour in the second potential plateau for the LixMn2O4-based electrode provided a possible kinetic-based explanation for the change of the high-frequency semi-circle.

  • 17.
    Brown, Shelley
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Baglien, Ida
    Uppsala Univ, Department of Materials Chemistry.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Edström, Kristina
    Uppsala Univ, Department of Materials Chemistry.
    Impact of SOC and Temperature on Surface Film Characteristics of LixNi0.8Co0.15Al0.05O2-based Positive Electrodes Harvested from an Accelerated HEV Ageing MatrixManuskript (Annet vitenskapelig)
  • 18.
    Brown, Shelley
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Temperature and SOC Dependence of the Lifetime Cycling and Calendar Performance of LixNi0.8Co0.15Al0.05O2/Graphite High-Power Batteries for Power-Assist HEV ApplicationsManuskript (Annet vitenskapelig)
  • 19.
    Brown, Shelley
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Mellgren, Niklas
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Vynnycky, Michael
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Impedance as a Tool for Investigating Aging in Lithium-Ion Porous Electrodes: II. Positive Electrode Examination2008Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, nr 4, s. A320-A338Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-power positive LixNi0.8Co0.15Al0.05O2 composite porous electrodes are known to be the main source of impedance increase in batteries based on GEN2 chemistry. The impedance of positive electrodes, both fresh and harvested from coin cells aged in an accelerated EUCAR hybrid electric vehicle lifetime matrix, was measured in a three-electrode setup and the results fitted with a physically based impedance model. A methodology for fitting the impedance data, including an optimization strategy incorporating a global genetic routine, was used to fit either fresh or aged positive electrodes simultaneously at different states of charge down to 0.5 mHz. The fresh electrodes had an exchange current density of approximately 1.0 A m(-2), a solid-phase diffusion coefficient of approximately 1.4 x 10(-1)5 m(2) s(-1), and a log-normal active particle size distribution with a mean radius of 0.25 mu m. Aged electrode impedance results were shown to be highly dependent on both the electrode state of charge and the pressure applied to the electrode surface. An aging scenario incorporating loss of active particles, coupled with an increase both in the local contact resistance between the active material and the conductive carbon and the resistance of a layer on the current collector, was shown to be adequate in describing the measured aged electrode impedance behavior.

  • 20.
    Brown, Shelley
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Ogawa, Keita
    Adv Engn Serv Co Ltd, Tsukuba.
    Kumeuchi, Youichi
    NEC Tokin Corp, Kanagawa.
    Enomoto, Shinsuke
    NEC Tokin Corp, Kanagawa.
    Uno, Masatoshi
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa.
    Saito, Hirobumi
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa.
    Sone, Yoshitsugu
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa.
    Abraham, Daniel
    Argonne Natl Lab, Div Chem Engn, Argonne.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites: I. Full Cell Results2008Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 185, nr 2, s. 1444-1453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lithium-ion batteries are a candidate for the energy storage system onboard low-earth-orbit satellites. Cycle life performance under both orbital and terrestrial conditions must be investigated in order to evaluate any inadvertent effects due to the former and the validity of the latter, with a successful comparison allowing for the extension of terrestrial experimental matrices in order to identify the effects of ageing. The orbital Performance of LixMn2O4-based pouch cells onboard the microsatellite REIMEI was monitored and compared with terrestrial experiments, with the cells found to be unaffected by orbital conditions. A lifetime matrix of different cycling depths-of-discharge (DODs: 0,20,40%) and temperatures (25, 45 degrees C) was undertaken with periodic reference performance tests. A decrease in both the cell end of-discharge cycling voltage and capacity was accelerated by both higher temperatures and larger DODs. Impedance spectra measured for all ageing conditions indicated that the increase was small, manifested in a state-of-charge dependent increase of the high-frequency semi-circle and a noticeable increase in the high-frequency real axis intercept. An evaluation of the change of both the resistance and capacity of 3 Ah cells led to the development of a potential prognostic state-of-health indicator. The use of elevated temperatures to accelerate cell ageing was validated.

  • 21.
    Brown, Shelley
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Ogawa, Keita
    Adv Engn Serv Co Ltd, Tsukuba.
    Kumeuchi, Youichi
    NEC Tokin Corp, Kanagawa .
    Enomoto, Shinsuke
    NEC Tokin Corp, Kanagawa .
    Uno, Masatoshi
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Kanagawa.
    Saito, Hirobumi
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Kanagawa.
    Sone, Yoshitsugu
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Kanagawa.
    Abraham, Daniel
    Argonne Natl Lab, Div Chem Engn.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites: II. Harvested Electrode Examination2008Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 185, nr 2, s. 1454-1464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lithium-ion batteries area candidate for the energy storage system onboard low-earth-orbit satellites. Terrestrial experiments are able to capture the performance degradation of cells in orbit, therefore providing the opportunity for lifetime investigations. The lifetime performance of 3 Ah commercial LixMn2O4-based pouch cells was evaluated in a matrix of different cycling depths-of-discharge (DODs: 0, 20,40%) and temperatures (25, 45 degrees C). Aged cells were disassembled and the electrochemical performance of harvested electrodes investigated with two- and three-electrode pouch cells. The positive electrode had a larger decrease in capacity than the negative electrode. Both the positive and negative electrode contributed to the increase of cell impedance measured at high states-of-charge (SOCs). The data at low SOCs indicated that the increase of cell impedance was associated with the positive electrode, which showed a significant increase in the magnitude of the high-frequency semi-circle. This SOC-dependence was observed for cells cycled for either extended periods of time or at higher temperatures with a 40% DOD swing. Low-current cycling of positive electrodes revealed a change in the second potential plateau, possibly reflecting a structural change of the LixMn2O4. This could impact on the electrode kinetics and provide a possible explanation for the SOC-dependent change of the impedance.

  • 22.
    Brumboiu, Iulia Emilia
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Prokopiou, G.
    Kronik, L.
    Brena, B.
    Valence electronic structure of cobalt phthalocyanine from an optimally tuned range-separated hybrid functional2017Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, nr 4, artikkel-id 044301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse the valence electronic structure of cobalt phthalocyanine (CoPc) by means of optimally tuning a range-separated hybrid functional. The tuning is performed by modifying both the amount of short-range exact exchange (α) included in the hybrid functional and the range-separation parameter (γ), with two strategies employed for finding the optimal γ for each α. The influence of these two parameters on the structural, electronic, and magnetic properties of CoPc is thoroughly investigated. The electronic structure is found to be very sensitive to the amount and range in which the exact exchange is included. The electronic structure obtained using the optimal parameters is compared to gas-phase photo-electron data and GW calculations, with the unoccupied states additionally compared with inverse photo-electron spectroscopy measurements. The calculated spectrum with tuned γ, determined for the optimal value of α = 0.1, yields a very good agreement with both experimental results and with GW calculations that well-reproduce the experimental data.

  • 23. Bultel, Yann
    et al.
    Wiezell, Katarina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Jaouen, Frédéric
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Ozil, P.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Investigation of mass transport in gas diffusion layer at the air cathode of a PEMFC2005Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, nr 3, s. 474-488Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a polymer electrolyte membrane fuel cell (PEMFC), slowdiffusion in the gas diffusion electrode may induce oxygen depletion when using air at the cathode. This work focuses on the behavior of a single PEMFC built with a Nafion® based MEA and an E-TEK gas diffusion layer and fed at the cathode with nitrogen containing 5, 10 and 20% of oxygen and working at different cell temperatures and relative humidities. The purpose is to apply the experimental impedance technique to cells wherein transport limitations at the cathode are significant. In parallel, a model is proposed to interpret the polarization curves and the impedance diagrams of a single PEMFC. The model accounts for mass transport through the gas diffusion electrode. It allows us to qualitatively analyze the experimental polarization curves and the corresponding impedance spectra and highlights the intra-electrode processes and the influence of the gas diffusion layer.

  • 24. Chen, Hong
    et al.
    Zhao, Huishuang
    Yu, Zheng-Bao
    Wang, Lei
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Sun, Licheng
    Sun, Junliang
    Construct Polyoxometalate Frameworks through Covalent Bonds2015Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 54, nr 17, s. 8699-8704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An emerging strategy for exploring the application of polyoxometalates (POMs) is to assemble POM clusters into open-framework materials, especially inorganic organic hybrid three-dimensional (3D) open-framework materials, via the introduction of different organic linkers between the POM clusters. This strategy has yielded a few 3D crystalline POMs of which a typical class is the group of polyoxometalate metal organic frameworks (POMMOFs). However, for reported POMMOFs, only coordination bonds are involved between the linkers and POM clusters, and it has not yet produced any covalently bonded polyoxometalate frameworks. Here, the concept of "covalently bonded POMs (CPOMs)" is developed. By using vanadoborates as an example, we showed that the 3D CPOMs can be obtained by a condensation reaction through the oxolation mechanism of polymer chemistry. In particular, suitable single crystals were harvested and characterized by single-crystal X-ray diffraction. This work forges a link among polymer science, POM chemistry, and open-framework materials by demonstrating that it is possible to use covalent bonds according to polymer chemistry principles to construct crystalline 3D open-framework POM materials.

  • 25. Chen, Si
    et al.
    Nyholm, Leif
    Jokilaakso, Nima
    KTH, Skolan för bioteknologi (BIO), Molekylär Bioteknologi.
    Karlström, Amelie Eriksson
    KTH, Skolan för bioteknologi (BIO), Molekylär Bioteknologi.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Smith, Ulf
    Zhang, Shi-Li
    Current Instability for Silicon Nanowire Field-Effect Sensors Operating in Electrolyte with Platinum Gate Electrodes2011Inngår i: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 14, nr 7, s. J34-J37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Current instability is observed for silicon nanowire field-effect transistors operating in electrolytes with Pt gate electrodes. A comparative study involving an Ag/AgCl-reference gate electrode reveals that the effect results from a drift in the potential at the Pt-electrode/electrolyte interface. In a phosphate buffer saline of pH 7.4, the stabilization of the potential of the Pt electrode was found to require approximately 1000 s. A concurrent potential drift, with a comparable time constant, occurring at the electrolyte/oxidized-nanowire interface rendered a complex device current response which complicated the interpretation of the results.

  • 26. Cheng, Minglun
    et al.
    Wang, Mei
    Zheng, Dehua
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Effect of the S-to-S bridge on the redox properties and H-2 activation performance of diiron complexes related to the [FeFe]-hydrogenase active site2016Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, nr 44, s. 17687-17696Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three biomimetic models of the [FeFe]-hydrogenase active site, namely diiron dithiolates of [(mu-edt){Fe(CO)(3)}{Fe(CO)(kappa(2)-PNP)}] (1, edt = ethane-1,2-dithiolate, PNP = Ph2PCH2N(nPr)CH2PPh2), [(mu bdtMe){Fe(CO)(3)}{Fe(CO)(kappa(2)-PNP)}] (2, bdtMe = 4-methylbenzene-1,2-dithiolate), and [(mu-adtBn){Fe(CO)(3)} {Fe(CO)(kappa(2)-PNP)}] (3, adtBn = N-benzyl-2-azapropane-1,3-dithiolate), were prepared and structurally characterized. These complexes feature the same PNP ligand but different S-to-S bridges. Influence of the S-to-S bridge on the electrochemical properties and chemical oxidation reactivity of 1-3 was studied by cyclic voltammetry and by in situ IR spectroscopy. The results reveal that the S-to-S bridge has a considerable effect on the oxidation reactivity of 1-3 and on the stability of in situ generated single-electron oxidized complexes, [1](+), [2](+), and [3](+). The performances of [1](+) and [2](+) for H-2 activation were explored in the presence of a mild chemical oxidant, while rapid decomposition of [3](+) thwarted the further study of this complex. Gratifyingly, 1 was found to be catalytically active, although in a low turnover number, for H-2 oxidation in the presence of excess mild oxidant and a proton trapper under 1 atm H-2 at room temperature.

  • 27. Cieclik, Monika
    et al.
    Kot, M.
    Reczyński, W.
    Engvall, Klas
    Rakowski, W.
    Kotarba, Andrzej
    Parylene coatings on stainless steel 316L surface for medical applications - Mechanical and protective properties2012Inngår i: Materials Science and Engineering C, Vol. 32, nr 1, s. 31-35Artikkel i tidsskrift (Fagfellevurdert)
  • 28. Cieślik, Monika
    et al.
    Reczyński, W.
    Janus, A. M.
    Engvall, Klas
    Socha, R. P.
    Kotarba, Andrzej
    Metal release and formation of surface precipitate at stainless steel grade 316 and Hanks solution interface - Inflammatory response and surface finishing effects2009Inngår i: Corrosion Science, Vol. 51, nr 5, s. 1157-1162Artikkel i tidsskrift (Fagfellevurdert)
  • 29.
    Cornell, Ann
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Rodrigo, Manuel
    Univ Castilla La Mancha, Dept Chem Engn, Ciudad Real, Spain..
    Bouzek, Karel
    Univ Chem & Technol Prague, Prague, Czech Republic..
    Special Issue: 11th European Symposium in Electrochemical Engineering (ESEE 11) Foreword2018Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 48, nr 6, s. 559-560Artikkel i tidsskrift (Fagfellevurdert)
  • 30.
    Cucarella Cabañas, Victor
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Mark- och vattenteknik.
    Recycling Filter Substrates used for Phosphorus Removal from Wastewater as Soil Amendments2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis studied the viability of recycling filter substrates as soil amendments after being used in on-site systems for phosphorus (P) removal from wastewater. Focus was put on the materials Filtra P and Polonite, which are commercial products used in compact filters in Sweden. A prerequisite for this choice was to review filter materials and P sorption capacity. The filter substrates (Filtra P, Polonite and wollastonite tailings) were recycled from laboratory infiltration columns as soil amendments to a neutral agricultural soil and to an acid meadow soil to study their impacts on soil properties and yield of barley and ryegrass. The amendments tended to improve the yield and showed a liming effect, significantly increasing soil pH and the availability of P. In another experiment, samples of Filtra P and Polonite were equilibrated in batch experiments with the two soils in order to study the P dynamics in the soil-substrate system.  Batch equilibrations confirmed the liming potential of Filtra P and Polonite and showed that improved P availability in soils was strongly dependent on substrate P concentration, phase of sorbed P, and soil type. Finally, samples of Polonite used for household wastewater treatment were recycled as soil amendments to a mountain meadow and to an agricultural field for wheat cropping. The liming effect of Polonite was confirmed under field conditions and the results were similar to those of lime for the mountain meadow soil. However, the results were quite different for the agricultural field, where Polonite did not affect soil pH or any other chemical and physical soil properties investigated and had no impact on wheat yield and quality. The results from field experiments suggested that Polonite can be safely recycled to meadows and cropping fields at rates of 5-10 ton ha-1 but long-term studies are needed to forecast the effects of accumulation.

  • 31.
    Dahlin, Oskar
    KTH, Skolan för kemivetenskap (CHE).
    Syntes och karakterisering av ogiftiga organiska metall halid halvledare för solceller2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The endeavor to have more efficient solar cells and as environmentally beneficial as possible are the driving forces for this work. The way to reach this is by research to better the understanding of the mechanisms and parameters that govern the performance of solar cells. New materials are essential to develop because the current ones lack stability and are water, temperature and UV-radiation sensitive. In this work the lead (Pb2+), which is poisonous and hazardous is intended to be replaced in the organic metal halide (OMH) perovskite structure. This is tested with gold or silver combined with bismuth and silver by itself. Also trimethylsulfonium gold or silver iodides are investigated. The methylammonium cation is also substituted to cesium. The perovskite material both absorbs light and transports charges in the solar cells. Materials based on AuI/AgI, BiI3 and CH3NH3I and AuI/AgI and [Me3S]I and AgI, BiI3 and CsI were synthesized and analyzed by XRD on thin film and mesoporous substrate and Raman spectroscopy to determine material structure and bonding. J-V measurements were performed to see the function in solar cells. After this conductivity and absorption parameters were determined by an electrical conductivity test and UV-vis absorption spectroscopy.

    XRD measurements indicate that the perovskite structure could have been obtained because the materials match with the XRD spectra of [20] foremost T3, T5 and T6, Cs1 and Cs2. In T7 some new structure is formed. The bismuth could be partially substituted by silver as the metal cation. The samples are quite amorphous, but still containing crystalline peaks, the product material could be a mixture of a crystalline and an amorphous phase. The crystalline phase could have the desired perovskite structure. To have mesoporous TiO2 as substrate seem to enhance a more crystalline structured material. All the materials seem to have formed some new structures because the pure reactants does not seem to be present, exceptions could be P1 and T1 that contained AuI. The change of cation from methylamine to cesium though results in a shift of the peak positions because of the change of cation size as in [20], but the structure is most likely the same.

    Raman spectroscopy indicate that there is a change in structure, some new bond being present, when increasing the methylamine ratio for the presumed methylammonium silver bismuth iodide perovskites. This concerns materials T5, T6, T7 with increasing ratio of methylamine. This new bond is most pronounced in T7 where the methylamine content is the highest. Both Silver and bismuth iodide bonds seem to be present and cannot be coupled to be the pure reactants recrystallizing and some new bonds of these are present in all materials to some extent. The organic bond vibration has low intensity and might indicate that there is not so much organic cation present in the product and thus the probability of having the desired product anion decreases.

    The solar cells made with Spiro-OMeTAD were 700-4000 times more efficient than those made with Sulphur polymer HTM.

    Solar cells made with Spiro-OMeTAD as HTM gives slightly higher efficiency when increasing the methylammonium cation ratio. For cesium as cation the combined metal cation constellation with bismuth and silver gives a little higher efficiency than bismuth alone. Methylammonium as cation gives a higher efficiency than cesium.

    Solar cells made with Sulphur polymer HTM show approximately 3-30 times higher efficiency with methylammonium as cation compared to cesium as cation. HTM material seem to affect the perovskite material making some of the cells completely transparent and some of them paler, water in the solvent chlorobenzene can be a possible explanation. The transparency can be the reason for the low efficiency obtained for the solar cells. Also the measurement methodology of these solar cells can also have been false, measuring the contacts, and the etching procedure could be another source of this.

    The solar cells had quite low efficiencies compared to [20], although same presumed material and procedure has been used and thus there might be something wrong in the accuracy of the manufacturing. The cells should probably been made several times and possible sources of error should be analyzed and corrected for.

    The materials were all relatively conductive. P1 gave the highest conductivity, almost three times higher than for methylammonium lead iodide that has a conductivity of 1,1x10-4 s/cm [3]. Increasing the methylammonium ratio gave an increase of the conductivity both with bismuth and silver as metal cations and silver alone. The increase of the methylammonium ratio might result in a new structure formed which has lattice planes that are more conductive. A change of gold to silver for the trimethylsulfonium iodide materials gave a large decrease in conductivity.

    The materials have different absorption curves meaning that they have different bandgaps and this indicates differences in structure. The bandgaps of all materials are indirect contrary to what is proven to be the case for perovskites that are believed to have direct bandgaps in general. To have indirect bandgaps requires a shift in momentum in the electronic transitions and is not as beneficial as having direct bandgaps. Compared to methylammonium lead iodide that has a direct bandgap of 1,6 eV, the bandgaps are at least 0,5 eV higher and range between 2,2-2,36 eV. P1 had a low bandgap of 1,6 eV meaning it absorbs a wide range of wavelengths.

    The conductivity does not seem to be the obstacle and the cells that are not transparent absorb light. It is highly possible that the low solar cell performance, at least to a certain extent, has to do with the production process. The low scan rate could also affect the low efficiencies and HTM Spiro-OMeTAD should be used.

    Currently the efficiency of the perovskite materials with silver/bismuth, gold/bismuth and silver are too low, and not able to substitute lead in the perovskite structure solar cells. Neither trimethylsulfonium gold or silver iodide cells nor cesium perovskites have enough efficiency at present. The conductivities for the materials are promising and the materials that are not completely transparent absorb light.

  • 32. Davoodi, Ali
    et al.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Parvizi, Reza
    Minuscule device for hydrogen generation/electrical energy collection system on aluminum alloy surface2011Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, nr 4, s. 2855-2859Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cogeneration of hydrogen and electrical energy in a single system is still a challenging issue. In this work, in a micro scale, a novel miniaturized system is introduced to capture the electrical energy of produced hydrogen on aluminum alloy by using an ultra-microelectrode based on scanning electrochemical microscopy (SECM). Sophisticated nanosize atomic force microscopy (AFM) based SECM probe could collect the electrochemical current close proximity distance from the aluminum surface to attain the highest possible current efficiency. Various collected current levels were associated to the aluminum microstructure constituents. It is expected that future development in instrumentation could principally facilitate SECM as a tool for hydrogen economy.

  • 33.
    Delandar, Arash Hosseinzadeh
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gorbatov, O. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering. Applied Physics, Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187, Luleå, Sweden; Laboratory for Mechanics of Gradient Nanomaterials, Nosov Magnitogorsk State Technical University, 455000, Magnitogorsk, Russia.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gornostyrev, Yu. N.
    Ryssland.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. National University of Science and Technology ”MISiS”, 119049, Moscow, Russia.
    Ab-initio based search for late blooming phase compositions in iron alloys2018Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 509, s. 225-236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a systematic analysis, based on ab initio calculations, of concentrated solute arrangements and precipitate phases in Fe-based alloys. The input data for our analysis are the calculated formation and interaction energies of point defects in the iron matrix, as well as the energies of ordered compounds that represent end-members in the 4-sublattice compound energy model of a multicomponent solid solution of Mg, Al, Si, P, S, Mn, Ni, and Cu elements and also vacancies in bcc Fe. The list of compounds also includes crystal structures obtained by geometric relaxation of the end-member compounds that in the cubic structure show weak mechanical instabilities (negative elastic constants) and also the G-phase Mn-6(Ni,Fe)(16)(Si,P)(7) having a complex cubic structure. A database of calculated thermodynamic properties (crystal structure, molar volume, enthalpy of formation, and elastic constants) of the most stable late-blooming-phase candidates is thus obtained. The results of this ab initio based theoretical analysis compare well with the recent experimental observations and predictions of thermodynamic calculations employing Calphad methodology.

  • 34. Dermenci, K.B.
    et al.
    Turan, S.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Effect of cathode slurry composition on the electrochemical properties of Li-ion batteries2015Inngår i: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 66, nr 9, s. 285-293Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance difference between commercial and laboratory scale cells remains a problem to be solved. Different way of battery electrode preparation is considered to be the main reason underlying various battery performance. In this work, the effect of slurry composition on electrochemical properties of Li-ion batteries is reported. Slurry preparation with various compositions of LiFePO4 active material (76-88%), PVdF binder (6-12%) and Super P Carbon conductive additive (6-12%) has been studied. Charge-discharge curves and capacity fade of electrodes are also investigated. Selected electrodes were pressed in order to see the effect of pressing on the final performance. Results showed that varying PVdF and carbon content mainly effects charge-discharge characteristics. For unpressed samples, higher amount of PVdF and carbon could result higher maximum specific capacity and lower internal resistance during lithiation and delithiation of positive electrode. Pressing reduces the distance between slurry particles, which enhances the conductivity of the prepared cell.

  • 35. Di, Jing
    et al.
    Chen, Mingming
    Wang, Chengyang
    Zheng, Jiaming
    Fan, Liangdong
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Samarium doped ceria-(Li/Na)(2)CO3 composite electrolyte and its electrochemical properties in low temperature solid oxide fuel cell2010Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, nr 15, s. 4695-4699Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A composite of samarium doped ceria (SDC) and a binary carbonate eutectic (52 mol% Li2CO3/48 mol% Na2CO3) is investigated with respect to its morphology, conductivity and fuel cell performances. The morphology study shows the composition could prevent SDC particles from agglomeration. The conductivity is measured under air, argon and hydrogen, respectively. A sharp increase in conductivity occurs under all the atmospheres, which relates to the superionic phase transition in the interface phases between SDC and carbonates. Single cells with the composite electrolyte are fabricated by a uniaxial die-press method using NiO/electrolyte as anode and lithiated NiO/electrolyte as cathode. The cell shows a maximum power density of 590 mW cm(-2) at 600 degrees C, using hydrogen as the fuel and air as the oxidant. Unlike that of cells based on pure oxygen ionic conductor or pure protonic conductor, the open circuit voltage of the SDC-carbonate based fuel cell decreases with an increase in water content of either anodic or cathodic inlet gas, indicating the electrolyte is a co-ionic (H+/O2-) conductor. The results also exhibit that oxygen ionic conductivity contributes to the major part of the whole conductivity under fuel cell circumstances. (C) 2010 Elsevier B.V. All rights reserved.

  • 36. Djouambi, Nadia
    et al.
    Bougheloum, Chafika
    Messalhi, Abdelrani
    Bououdina, Mohamed
    Banerjee, Amitava
    Chakraborty, Sudip
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    New Concept on Photocatalytic Degradation of Thiophene Derivatives: Experimental and DFT Studies2018Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 27, s. 15646-15651Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the photocatalytic degradation of seven sulfur compounds (2-methylthiophene, 3-methylthiophene, 2-phenylthiophene, 3-phenylthiophene, 2,5-diphenylthiophene, 2-(2-thienyl) pyridine, and 2-(3-thienyl) pyridine in semiaqueous medium are compared to thiophene. The apparent-reaction-rate constant (k) is found to decrease in the following order: 2,5-diphenylthiophene > 2-(2-thienyl) pyridine > 2-penhylthiophene methylthiophene > 3-penhylthiophene > 2-methylthiophene > 2-(3-thienyl) pyridine > 3-thiophene. From the data obtained by UV light absorption (lambda(max)) measurements and electronic structure calculations (frontier orbitals energy, global hardness, and global softness), the kinetic parameters of the reaction have been determined. Among the studied compounds, thiophene with a high lambda(max) and low calculated LUMO-HOMO gap energy has showed higher activity under UV irradiation. Interestingly, a lower activity is observed with low lambda(max) and high LUMO-HOMO gap energy. This demonstrates, for the first time, that the reactivity depends essentially on the thermodynamic stability of the sulfur compound rather than on the nature or the position of the substituent on the ring.

  • 37. Dobrota, Ana S.
    et al.
    Pasti, Igor A.
    Mentus, Slavko V.
    Skorodumova, Natalia V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    A DFT study of the interplay between dopants and oxygen functional groups over the graphene basal plane - implications in energy-related applications2017Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, nr 12, s. 8530-8540Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the ways graphene can be functionalized is of great importance for many contemporary technologies. Using density functional theory calculations we investigate how vacancy formation and substitutional doping by B, N, P and S affect the oxidizability and reactivity of the graphene basal plane. We find that the presence of these defects enhances the reactivity of graphene. In particular, these sites act as strong attractors for OH groups, suggesting that the oxidation of graphene could start at these sites or that these sites are the most difficult to reduce. Scaling between the OH and H adsorption energies is found on both reduced and oxidized doped graphene surfaces. Using the O-2 molecule as a probe we show that a proper modelling of doped graphene materials has to take into account the presence of oxygen functional groups.

  • 38. Dong, Wenjing
    et al.
    Yaqub, Azra
    Janjua, Naveed K.
    Raza, Rizwan
    Afzal, Muhammad
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Faculty of Physics and Electronic Science, Hubei University, Wuhan, Hubei, China.
    All in One Multifunctional Perovskite Material for Next Generation SOFC2016Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 193, s. 225-230Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multifunctional roles of La0.2Sr0.25Ca0.45TiO3 (LSCT) perovskite material as anode, cathode, and electrolyte for low temperature solid oxide fuel cell (LT-SOFC) are discovered for the first time, and have been investigated via electrochemical impedance spectroscopy (EIS) and fuel cell (FC) measurements. LSCT resistance decreases prominently in FC environment as shown in this study. An improved performance was observed by compositing LSCT with samaria doped ceria (SDC) at 550 degrees C when the FC power density increased from tens of mW cm(-2) for the pure LSCT system up to hundreds of mW cm(-2). The improved conductivity of LSCT-SDC composite is highlighted. The multifunctionality of LSCT as cathode, anode and electrolyte could be attributed to different conducting behavior at high and low oxygen partial pressures and ionic conduction at intermediate oxygen partial pressures. These new discoveries not only indicate great potential for exploring multifunctional perovskites for the next generation SOFC, but also deepen SOFC science and develop new technologies.

  • 39.
    Ekeroth, Ella
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Radiation Induced Oxidative Dissolution of UO22006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Sammanfattning

    Denna doktorsavhandling berör oxidativ upplösning av UO2 (som modellsubstans för utbränt kärnbränsle) orsakad av radiolys av vatten samt effekten av H2 på denna denna process.

    Hastighetskonstanter för oxidation av UO2-pulver med olika oxidanter såsom H2O2 har bestämts experimentellt. Logaritmen för andra ordningens hastighetskonstant, ln k, för oxidation av UO2 uppvisar ett linjärt beroende av oxidantens en-elektronreduktionspotential, E0. Detta indikerar att det hastighetsbestämmande steget för oxidation av UO2 är en en-elektronöverföring. Oxidationshastigheten för reaktionen mellan UO2 och OH• samt CO3•- är diffusionskontrollerad, k = 10-3 m/min.

    Effekten av karbonat på oxidationskinetiken har studerats där H2O2 har adderats till suspensioner innehållande UO2-pulver. Andra ordningens hastighetskonstant för den rena oxidationsreaktionen mellan UO2 och H2O2 har bestämts till 4.4 x 10 -6 m/min. Den karbonatberoende upplösningshastigheten har visat sig vara diffusionskontrollerad. Hastighetskonstanten för upplösning av UO22+ i vatten fritt från karbonat är (7 +- 1) x 10-8 mol m-2 s-1.

    Den relativa effektiviteten (per elektron) för en- respektive två-elektronoxidanter som orsakar upplösning av UO2 har studerats. Utbytena för upplösning med en-elektronoxidanter har ett starkt koncentrationsberoende m.a.p. oxidanten (särskilt vid låga konc.).

    Reduktion av UO22+ i karbonatlösningar med H2 (p = 40 bar) vid olika temperaturer har studerats som en funktion av reaktionstiden. Hastighetskonstanten och aktiveringsenergin har bestämts, k298 = 3.6 x 10-9 M-1 s-1 och Ea = 130 +- 24 kJ/mol. Reduktionen av UO22+ till UO2 sker i frånvaro av en katalysator.

    Den relativa inverkan av radiolysprodukter på oxidativ upplösning av UO2 har klargjorts. Mängden upplöst UO22+ mättes som en funktion av tiden i gasmättade gamma-bestrålade karbonatlösningar innehållande en UO2-kuts. Den simulerade upplösningshastigheten beräknades utifrån ytarea, oxidantkoncentrationer och hastighetskonstanter erhållna från det linjära sambandet (se ovan). De simulerade hastigheterna jämfördes med de experimentellt bestämda upplösningshastigeherna och korrelation är förhållandevis bra. Därmed kan inverkan av varje enskild oxidant i det undersökta systemet uppskattas. Endast de molekylära oxidanterna är av vikt i system som är relevanta för säkerhetsanalyser av ett djupförvar.

  • 40.
    Ekeroth, Ella
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Jonsson, Mats
    KTH, Tidigare Institutioner                               , Kemi.
    Oxidation of UO2 by radiolytic oxidants2003Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 322, nr 03-feb, s. 242-248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The kinetics of UO2 oxidation by H2O2 has been studied using aqueous suspensions Of UO2-powder. The second order,rate constant for the reaction between H2O2 and UO2 has been determined to 8 x 10(-7) m/min (based on the surface to solution volume ratio) in the absence of carbonate. By studying the reaction between UO2 and other oxidants, it is possible to draw conclusions concerning the mechanism. The logarithm of the second order rate constant, ln k, for UO2 oxidation appears to be linearly related to the one-electron reduction potential, E-0, of the oxidant. This indicates that the rate limiting step in the oxidation of UO2 is one-electron transfer. A Fenton like mechanism is plausible for the reaction between UO2 and H2O2. The diffusion controlled rate constant in this particular system is approximately 10(3) m/min, and therefore the reactions with OH- and CO3- are estimated to be diffusion controlled.

  • 41.
    Ekeroth, Ella
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Jonsson, Mats.
    KTH, Tidigare Institutioner, Kemi.
    Eriksen, Trygve
    KTH, Tidigare Institutioner, Kemi.
    Ljungqvist, Kristina
    KTH, Tidigare Institutioner, Kemi.
    Kovacs, Sandor
    Puigdomenech, Ignasi
    Reduction of UO22+ by H-22004Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 334, nr 1, s. 35-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reactivity of H, towards UO22+ has been studied experimentally using a PEEK coated autoclave where the UO22+ concentration in aqueous solution containing 2 mM carbonate was measured as a function of time at p(H2) similar to 40 bar. The experiments were performed in the temperature interval 74-100 degreesC. In addition, the suggested catalytic activity of UO2 on the reduction of UO22+ by H-2 was investigated. The results clearly show that H-2 is capable of reducing UO22+ to UO2 without the presence of a catalyst. The reaction is of first order with respect to UO22+. The activation energy for the process is 130 +/- 24 U mol(-1) and the rate constant is k(298K) = 3.6 x 10(-9) l mol(-1) s(-1). The activation enthalpy and entropy for the process was determined to 126 kJ mol(-1) and 16.5 J mol(-1) K-1, respectively. Traces of oxygen were shown to inhibit the reduction process. Hence, the suggested catalytic activity of freshly precipitated U02 on the reduction of UO22+ by H-2 could not be confirmed.

  • 42.
    Ekeroth, Ella
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    The relative impact of radiolysis products in radiation induced oxidative dissolution of UO22006Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 355, nr 1-3, s. 38-46Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relative impact of radiolysis products in radiation induced oxidative dissolution Of UO2 has been studied experimentally. The experiments were performed by y-irradiating an aqueous solution containing HCO3 and a UO2-pellet. The U(VI) concentration in the solution was measured as a function of irradiation time. The aqueous solution was saturated with Ar, N2O, N2O/O-2 (80/20), air and O-2 in order to vary the conditions and the initial oxidant yields. The measured rate of oxidation was significantly higher for the O-2- and air saturated systems compared to the other systems. Using oxidant concentrations derived from numerical simulations of the corresponding homogeneous systems and previously determined rate constants for oxidation Of UO2, the relative trend in rate of oxidation in the different systems was reproduced. The results from the simulations were also used to estimate the relative impact of the oxidative radiolysis products as a function of irradiation time, both for gamma- and alpha-irradiated systems. For 7-irradiated systems saturated with Ar, air or 02, the most important oxidant is H2O2 while for N2O- and N2O/O-2-saturated systems the most important oxidant is CO3.-. For a-irradiated systems the most important oxidant was found to be H2O2.

  • 43.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Evaluating Cathode Catalysts in the Polymer Electrolyte Fuel Cell2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The polymer electrolyte membrane fuel cell (PEMFC) converts the chemical energy of hydrogen and oxygen (air) into usable electrical energy. At the cathode (the positive electrode), a considerable amount of platinum is generally required to catalyse the sluggish oxygen reduction reaction (ORR). This has implications regarding the cost in high-power applications, and for making a broad commercialisation of the PEMFC technology possible, it would be desirable to lower the amount of Pt used to catalyse the ORR.

    In this thesis a number of techniques are described that have been developed in order to investigate catalytic activity at the cathode of the PEMFC. These methodologies resemble traditional three-electrode research in liquid electrolytes, including cyclic voltammetry in inert gas, but with the advantage of performing the experiments in the true PEMFC environment.

    From the porous electrode studies it was seen that it is possible to reach mass activities close to 0.2 gPt/kW at potentials above 0.65 V at 60 ◦C, but that the mass activities may become considerably lower when raising the temperature to 80 ◦C and changing the measurement methodology regarding potential cycling limits and electrode manufacturing.

    The model electrode studies rendered some interesting results regarding the ORR at the Pt/Nafion interface. Using a novel measurement setup for measuring on catalysed planar glassy carbon disks, it was seen that humidity has a considerable effect on the ORR kinetics of Pt. The Tafel slopes become steeper and the activity decreases when the humidity level of the inlet gases decreases. Since no change in the the electrochemical area of the Pt/Nafion interface could be seen, these kinetic phenomena were ascribed to a lowered Pt oxide coverage at the lower humidity level, in combination with a lower proton activity.

    Using bi-layered nm-thick model electrodes deposited directly on Nafion membranes, the behaviour of TiO2 and other metal oxides in combination with Pt in the PEMFC environment was investigated. Kinetically, no intrinsic effect could be seen for the model electrodes when adding a metal oxide, but compared to porous electrodes, the surface (specific) activity of a 3 nm film of Pt deposited on Nafion seems to be higher than for a porous electrode using ∼4 nm Pt grains deposited on a carbon support. Comparing the cyclic voltammograms in N2, this higher activity could be ascribed to less Pt oxide formation, possibly due to a particle size effect.

    For these bi-layered films it was also seen that TiO2 may operate as a proton-conducting electrolyte in the PEMFC.

  • 44.
    Ekström, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hanarp, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gustavsson, Marie
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Fridell, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A Novel Approach for Measuring Catalytic Activity of Planar Model Catalysts in the Polymer Electrolyte Fuel Cell Environment2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 153, nr 4, s. A724-A730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrochemical oxygen reduction reaction on nanostructured supported platinum electrodes is measured using a newly developed solid-state polymer electrolyte electrochemical cell. Measurements were made on three types of catalytic surfaces on glassy carbon supports: nanostructured model electrodes prepared by colloidal lithography, a thin thermally evaporated Pt film, and a pure glassy carbon surface. Measurements in nitrogen and oxygen at several different humidities were performed at 60 degrees C in a fuel-cell-like environment. Lowering humidity showed a higher Tafel slope at high potentials for oxygen reduction on the nanostructured catalyst. Good agreement between the electrochemical active area from the hydrogen adsorption peaks and the catalytic area determined from scanning electron microscopy images was found. No significant change of the electrochemically active area with humidity could be found. Double-layer capacitance and oxygen reduction currents increased with increased humidification temperatures.

  • 45.
    Ekström, Henrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wickman, Björn
    Chalmers tekniska högskola, Göteborg.
    Gustavsson, Marie
    Chalmers tekniska högskola, Göteborg.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Nanometer-thick films of titanium oxide acting as electrolyte in the polymer electrolyte fuel cell2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, nr 12, s. 4239-4245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    0-18nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nation 117 membranes, and used as thin spacer electrolyte layers between the Nation and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 degrees C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activity is seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte.

  • 46.
    Elger, Ragna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Swerea KIMAB.
    High temperature corrosion in biomass-fired energy applications: Alloying effects and test environment comparisons2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    To reduce the greenhouse effect, the use of renewable fuel has to be increased. As renewable fuel has different characteristics compared to fossil fuel regarding content of trace metals, alkali, chlorine and sulphur, the corrosion characteristics in high temperature energy processes have to be evaluated. This thesis concerns high temperature corrosion in the superheater region of a boiler and the syngas cooler area of a gasifier.

    For the superheater region, laboratory exposures were performed. The methods included a salt dip exposure, where samples were dipped in an equimolar solution of ZnCl2 and KCl, and two salt bed exposures with different chlorine concentrations, 10 and 20 wt%. Ranking of the materials showed that a Ni content above 10 wt% and Cr above 20 wt% reduced corrosion rates in the salt dip and in the 10% Cl salt bed exposure. For exposure in the 20% Cl bed, even higher alloying was needed. An alumina forming austenitic steel showed future potential in sulphidising-chlorinating environments.

    For the gasifier region, the effect of HCl in a simulated gasifier atmosphere was studied and also samples exposed in the syngas section of a biomass gasifier were investigated. Metal loss was low for all exposures and it was observed that chlorine had minor influence. For the plant exposed samples, a difference compared to that reported for coal gasifiers was the absence of FeS for the lowest alloyed steel. Instead, a deposit with pronounced content of Zn, Ca, S and O was present on the surface. Zinc was suggested to mitigate corrosion.

    Thermodynamic modelling was used to explain phases present and to predict the nitridation behaviour of an alumina forming austenitic steel. Equilibrium and kinetic modelling of the nitridation showed good coherence with the observed microstructures. However, the kinetic modelling resulted in larger nitridation depths than observed experimentally which was attributed to the presence of a thin oxide layer on the surface of the samples.

  • 47. Fako, Edvin
    et al.
    Dobrota, Ana S.
    Pasti, Igor A.
    Lopez, Nuria
    Mentus, Slavko V.
    Skorodumova, Natalia V.
    Lattice mismatch as the descriptor of segregation, stability and reactivity of supported thin catalyst films2018Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 3, s. 1524-1530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The increasing demand and high prices of advanced catalysts motivate a constant search for novel active materials with reduced contents of noble metals. The development of thin films and core-shell catalysts seems to be a promising strategy along this path. Using density functional theory we have analyzed a number of surface properties of supported bimetallic thin films with the composition A(3)B (where A = Pt and Pd, and B = Cu, Ag and Au). We focus on the surface segregation, dissolution stability and surface electronic structure. We also address the chemisorption properties of Pd3Au thin films supported by different substrates, by probing the surface reactivity with CO. We find a strong influence of the support in the case of mono- and bilayers, while the surface strain seems to be the predominant factor in determining the surface properties of supported trilayers and thicker films. In particular, we show that the studied properties of the supported trilayers can be predicted from the lattice mismatch between the overlayer and the support. Namely, if the strain dependence of the corresponding quantities for pure strained surfaces is known, the properties of strained supported trilayers can be reliably estimated. The obtained results can be used in the design of novel catalysts and predictions of the surface properties of supported ultrathin catalyst layers.

  • 48. Fan, Ke
    et al.
    Zou, Haiyuan
    Lu, Yue
    Beijing Univ Technol, Inst Microstruct & Properties Adv Mat, Beijing 100124, Peoples R China..
    Chen, Hong
    Li, Fusheng
    Liu, Jinxuan
    Sun, Licheng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Tong, Lianpeng
    Toney, Michael F.
    Sui, Manling
    Yu, Jiaguo
    Direct Observation of Structural Evolution of Metal Chalcogenide in Electrocatalytic Water Oxidation2018Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, nr 12, s. 12369-12379Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As one of the most remarkable oxygen evolution reaction (OER) electrocatalysts, metal chalcogenides have been intensively reported during the past few decades because of their high OER activities. It has been reported that electron-chemical conversion of metal OER chalcogenides into oxides/hydroxides would take place after the OER. However, the transition mechanism of such unstable structures, as well as the real active sites and catalytic activity during the OER for these electrocatalysts, has not been understood yet; therefore a direct observation for the electrocatalytic water oxidation process, especially at nano or even angstrom scale, is urgently needed. In this research, by employing advanced Cs-corrected transmission electron microscopy (TEM), a step by step oxidational evolution of amorphous electrocatalyst CoSx into crystallized CoOOH in the OER has been in situ captured: irreversible conversion of CoSx to crystallized CoOOH is initiated on the surface of the electrocatalysts with a morphology change via Co(OH)(2) intermediate during the OER measurement, where CoOOH is confirmed as the real active species. Besides, this transition process has also been confirmed by multiple applications of X-ray photoelectron spectroscopy (XPS), in situ Fourier-transform infrared spectroscopy (FTIR), and other ex situ technologies. Moreover, on the basis of this discovery, a high-efficiency electrocatalyst of a nitrogen-doped graphene foam (NGF) coated by CoSx has been explored through a thorough structure transformation of CoOOH. We believe this in situ and in-depth observation of structural evolution in the OER measurement can provide insights into the fundamental understanding of the mechanism for the OER catalysts, thus enabling the more rational design of low-cost and high-efficient electrocatalysts for water splitting.

  • 49.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Marton, Andras
    Johns Hopkins University.
    Narducci-Sarjeant, Amy A.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Influence of ion pairing on the oxidation of iodide by MLCT excited states2011Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, nr 15, s. 3830-3838Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The oxidation of iodide to diiodide, I2[radical dot]-, by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)3]2+, where deeb is 4,4[prime or minute]-(CO2CH2CH3)2-2,2[prime or minute]-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)3]2+ were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)3]2+* and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (KD = 1.0 +/- 0.01 [times] 105 M-1, kq = 4.8 [times] 1010 M-1 s-1). Excited state reactivity was observed to be the result of reductive quenching that yielded the reduced ruthenium compound, [Ru(deeb-)(deeb)2]+, and the iodine atom, I[radical dot]. In dichloromethane, excited state quenching was primarily static (photoluminescence amplitude quenching) and [Ru(deeb-)(deeb)2]+ formed within 10 ns, consistent with the formation of ion pairs in the ground state that react rapidly upon visible light absorption. In both solvents the appearance of I2[radical dot]- could be time resolved. In acetonitrile, the rate constant for I2[radical dot]- growth, 2.2 +/- 0.2 [times] 1010 M-1 s-1, was found to be about a factor of two slower than the formation of [Ru(deeb-)(deeb)2]+, indicating it was a secondary photoproduct. The delayed appearance of I2[radical dot]- was attributed to the reaction of iodine atoms with iodide. In dichloromethane, the growth of I2[radical dot]-, 1.3 +/- 0.4 [times] 1010 M-1 s-1, was similar to that in acetonitrile, yet resulted from iodine atoms formed within the laser pulse. These results are discussed within the context of solar energy conversion by dye-sensitized solar cells and storage via chemical bond formation.

  • 50.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Flash-Quench Technique Employed To Study the One-Electron Reduction of Triiodide in Acetonitrile: Evidence for a Diiodide Reaction Product2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 22, s. 10223-10225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The one-electron reduction of triiodide (I3?) by a reduced ruthenium polypyridyl compound was studied in an acetonitrile solution with the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [RuII(deeb)3]2+ by iodide generated the reduced ruthenium compound [RuII(deeb?)(deeb)2]+ and diiodide (I2??). The subsequent reaction of [RuII(deeb?)(deeb)2]+ with I3? indicated that I2?? was a product that appeared with a second-order rate constant of (5.1 ± 0.2) ? 109 M?1 s?1. After correction for diffusion and some assumptions, Marcus theory predicted a formal potential of ?0.58 V (vs SCE) for the one-electron reduction of I3?. The relevance of this reaction to solar energy conversion is discussed.

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