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  • 1.
    Abbasalizadeh, Aida
    et al.
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Venkatesan, Prakash
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Sietsma, Jilt
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Yang, Yongxiang
    Delft Univ Technol TU Delft, Dept Mat Sci & Engn, Mekelweg 2, NL-2628 CD Delft, Netherlands..
    Use of iron reactive anode in electrowinning of neodymium from neodymium oxide2019Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 310, s. 146-152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrolytic production of metallic neodymium is carried out in fused neodymium fluoride salts containing neodymium oxide. Two major challenges pertaining to neodymium production in fluoride salts are a) low solubility of neodymium oxide in fluoride melt, b) possibility of anodic gas evolution (CO, CO2, CF4, C2F6). In this study, iron is used as a reactive anode in the electrolysis process, promoting electrochemical dissolution of iron into the melt, preventing PFC (perfluorocarbon) gas evolution at the anode. Further, the rare earth oxide is converted to rare earth fluoride by the use of iron fluoride formed as the result of iron dissolution. Thus, the fluoridizing agent is constantly regenerated in-situ which enables the continuous conversion of neodymium oxide feed. The cathodic product is Nd-Fe alloy which can be used as a master alloy for the production of NdFeB magnets. 

  • 2.
    Adhikari, Arindam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pani, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Deidinaitei, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 12, s. 4239-4247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 3.
    Afzal, Muhammad
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Raza, R.
    Du, S.
    Lima, R.B.d
    Zhu, Bin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik. Hubei Univ, Fac Phys & Elect Technol, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Peoples R China.
    Synthesis of Ba0.3Ca0.7Co0.8Fe0.2O3-δ composite material as novel catalytic cathode for ceria-carbonate electrolyte fuel cells2015Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 178, s. 385-391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work reports a new composite BaxCa1-xCoyFe1-yO3-delta (BCCF) cathode material for advanced and low temperature solid oxide fuel cells (SOFCs). The BCCF-based composite material was synthesized by sol gel method and investigated as a catalytic cathode for low temperature (LT) SOFCs. XRD analysis of the as-prepared material revealed the dominating BCCF perovskite structure as the main phase accompanied with cobalt and calcium oxides as the secondary phases resulting into an overall composite structure. Structure and morphology of the sample was observed by Field Emission Scanning Electron Microscope (FE-SEM). In particular, the Ba0.3Ca0.7Co0.8Fe0.2O3-delta (BCCF37) showed a maximum conductivity of 143 S cm(-1) in air at 550 degrees C measured by DC 4 probe method. The BCCF at the optimized composition exhibited much higher electrical conductivities than the commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) perovskite cathode material. A maximum power density of 325 mW cm(-2) at 550 degrees C is achieved for the ceria-carbonate electrolyte fuel cell with BCCF37 as the cathode material.

  • 4. Behm, Mårten
    et al.
    Irvine, J. T. S.
    Influence of structure and composition upon performance of tin phosphate based negative electrodes for lithium batteries2002Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, nr 11, s. 1727-1738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tin oxide and amorphous tin borophosphates have recently received significant attention as possible new negative electrode materials for lithium batteries. In this study. we have carefully investigated a number of different well-characterised tin phosphates as electrodes in Li-ion cells, in order to better understand the mode of operation of these materials and how their performance is related to structure and composition. The materials that were investigated were crystalline cubic and layered SnP2O7, LiSn2(PO4)(3). Sn2P2O7, and Sn-3(PO4)(2). and amorphous Sn2BPO6. Cubic SnP2O7 showed the best performance with a reversible specific charge capacity of > 360 mA h g(-1) and a capacity retention of 96% over 50 cycles when cycled between 0.02 and 1.2 V versus Li-m. The three Sn(IV) materials showed lower initial reversible capacity but better capacity retention than the three Sn(II) materials in the study. Their higher proportion of inert matrix material can partly explain this. However. cubic SnP2O7 cycled significantly better than its layered polymorph. which shows that the structure of the starting material is also of great importance. Another important conclusion drawn front the results is that it is not necessary for the starting material to be amorphous, or if crystalline, to have small grain size, to cycle well. The three pyrophosphates all show an initial reduction capacity that corresponds to around 2 Li per P2O74- unit more than is predicted by theory. This might be explained by reductive break-up of the P 0 P bond.

  • 5. Bencsik, Gábor
    et al.
    Janáky, Csaba
    Endrődi, Balázs
    University of Szeged, Hungary.
    Visy, Csaba
    Electrocatalytic properties of the polypyrrole/magnetite hybrid modified electrode towards the reduction of hydrogen peroxide in the presence of dissolved oxygen2012Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 73, s. 53-58Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we report on the electrocatalytic behaviour of a polypyrrole/magnetite hybrid electrode towards the reduction of hydrogen peroxide. The electrocatalytic activity of the composite electrode was demonstrated by cyclic voltammetric and chrono-amperometric measurements in comparison with the identically prepared neat polymer film. The stationary reduction currents, measured at an appropriately chosen potential (here at E = -0.3 V), plotted against the peroxide concentration gave a perfect linear correlation in nitrogen atmosphere in the micromolar concentration range. The performance of the composite electrode was not affected by the presence of sulphate, nitrate or chloride anions. In the presence of dissolved oxygen a complex electrocatalytic activity was observed, involving the reduction of both oxygen and H2O2. However, a linear dependence was found also in oxygen containing media, although with much higher currents, but with the same slope (even at different oxygen concentrations). This fact may trigger the development of such hybrid electrodes towards hydrogen peroxide sensors in different aqueous (including natural) samples.

  • 6.
    Bettini, Eleonora
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Eriksson, Tom
    Bostrom, Magnus
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Influence of metal carbides on dissolution behavior of biomedical CoCrMo alloy: SEM, TEM and AFM studies2011Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, nr 25, s. 9413-9419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of precipitate carbides on dissolution tendency and behavior of a biomedical CoCrMo alloy was investigated at microscopic scale. SEM/EDS, TEM/EDS and XRD were performed to characterize crystallographic structure and composition of different precipitate carbides. Scanning Kelvin probe force microscope (SKPFM) was used to evaluate relative nobility of the carbides. In addition to polarization curves, in situ electrochemical AFM (EC-AFM) measurements were performed to investigate the effect of the carbides on local dissolution processes. SEM/EDS, TEM/EDS and XRD characterizations showed non-uniform structure and composition of Cr and Mo carbides. SKPFM analysis suggested the carbide boundaries as preferential sites for corrosion/dissolution process. Cyclic polarization curves of the alloy in phosphate-buffered saline (PBS) solution showed a large current density increase above a certain potential, but only a small hysteresis loop during reverse scan. No noticeable pitting corrosion was observed by SEM after the experiments. In situ AFM images of the sample in PBS showed a stable surface at potentials in the passive region and around the potential corresponding to the current increase and slight etching-like dissolution around the carbides at higher potentials. Carbide boundaries are preferential sites for metal dissolution and carbides with non-uniform composition might exhibit different dissolution rates.

  • 7.
    Bettini, Eleonora
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Kivisäkk, Ulf
    Sandvik Materials Technology.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Study of corrosion behavior of a 22% Cr duplex stainless steel: influence of nano-sized chromium nitrides and exposure temperature2013Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 113, s. 280-289Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chromium nitrides may precipitate in duplex stainless steels during processing and their influence on the corrosion behavior is of great importance for the steel performance. In this study, the influence of nano-sized quenched-in chromium nitrides on the corrosion behavior of a heat treated 2205 duplex stainless steel was investigated at room temperature and 50 °C (just above critical pitting temperature). The microstructure was characterized by SEM/EDS and AFM analyses, and quenched-in nitrides precipitated in the ferrite phase were identified by TEM analysis. Volta potential mapping at room temperature suggests lower relative nobility of the ferrite matrix. Electrochemical polarization and in-situ AFM measurements in 1 M NaCl solution at room temperature show a passive behavior of the steel despite the presence of the quenched-in nitrides in the ferrite phase, and preferential dissolution of ferrite phase occurred only at transpassive conditions. At 50 °C, selective dissolution of the austenite phase was observed, while the ferrite phase with the quenched-in nitrides remained to be stable. It can be concluded that the finely dispersed quenched-in nitrides do not cause localized corrosion, whereas the exposure temperature has a strong influence on the corrosion behavior of the duplex stainless steel.

  • 8. Bora, Tanujjal
    et al.
    Kyaw, Htet H
    Dutta, Joydeep
    Center of Excellence in Nanotechnology, Asian Institute of Technology, Thailand.
    Zinc oxide–zinc stannate core–shell nanorod arrays for CdS quantum dot sensitized solar cells2012Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 68, s. 141-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanorod arrays of zinc oxide–zinc stannate core–shell photoelectrodes were prepared by a simple hydrothermal process and cadmium sulfide (CdS) quantum dot sensitized solar cells were fabricated. The photocurrent density of the core–shell photoelectrode was found to improve by ∼2.4 times compared to ZnO nanorod photoelectrodes, due to improved surface area and charge transport in the core–shell photoelectrodes. With a thin layer of ZnS on the CdS quantum dot surface, the core–shell quantum dot sensitized solar cell demonstrated maximum power conversion efficiency of 1.24% under 1 sun illumination (AM1.5).

  • 9. 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 PEMFC2005Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, nr 3, s. 474-488Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Bursell, Martin
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Pirjamali, M.
    Kiros, Yohannes
    KTH, Tidigare Institutioner                               , Kemiteknik.
    La0.6Ca0.4CoO3, La0.1Ca0.9MnO3 and LaNiO3 as bifunctional oxygen electrodes2002Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, nr 10, s. 1651-1660Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of perovskite catalysts was investigated for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte and at room temperature, supplied by oxygen or air. A meniscus cell was used to screen-test candidate catalysts for their bifunctionality and assess their activity for ORR at 3 mm depth of immersion (DOI) in the electrolyte. Based on the meniscus data LaNiO3, La0.1Ca0.9MnO3 and La0.6Ca0.4CoO3 were selected for further assessment in microelectrode and half-cell studies. Activity tests for the ORR and OER, Tafel slopes at high current densities and apparent activation energies for the ORR were determined using a microelectrode technique on samples of the selected perovskites, La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3 with and without graphite support. Tafel slopes of ca. 120 mV per decade and apparent activation energies of approximately 18 kcal mol(-1) were measured at high cathodic current densities. Cycle-life and performance of La0.1Ca0.9MnO3, La0.6Ca0.4CoO3 and LaNiO3-based gas-diffusion electrodes in half-cell configurations were tested at a constant current density of 25 mA cm(-2) With subsequent and intermittent polarizations. Similar activities resulted in the ORR, while increased numbers of cycles were observed for the La0.1Ca0.9MnO3-based electrode. Furthermore, electrode material compositions, especially PTFE contents were optimized to conform to the establishment of the three phase interactions of the electrode structure, Transmission Electron microscopy (TEM) and BET-surface area analyses were carried out in order to find out the morphological and surface properties of the perovskite materials.

  • 11.
    Carlson, Annika
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Shapturenka, Pavel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Björn
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Wreland Lindström, Rakel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Electrode parameters and operating conditions influencing the performance of anion exchange membrane fuel cells2018Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 277, s. 151-160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A deeper understanding of porous electrode preparation and performance losses is necessary to advance the anion exchange membrane fuel cell (AEMFC) technology. This study has investigated the performance losses at 50 °C for varied: Tokuyama AS-4 ionomer content in the catalyst layer, Pt/C loading and catalyst layer thickness at the anode and cathode, relative humidity, and anode catalyst. The prepared gas diffusion electrodes in the interval of ionomer-to-Pt/C weight ratio of 0.4–0.8 or 29–44 wt% ionomer content show the highest performance. Varying the loading and catalyst layer thickness simultaneously shows that both the cathode and the anode influence the cell performance. The effects of the two electrodes are shown to vary with current density and this is assumed to be due to non-uniform current distribution throughout the electrodes. Further, lowering the relative humidity at the anode and cathode separately shows small performance losses for both electrodes that could be related to lowered ionomer conductivity. Continued studies are needed to optimize, and understand limitations of, each of the two electrodes to obtain improved cell performance.

  • 12.
    Chang, Tingru
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Univ Sci & Technol Beijing, Peoples R China.
    Jin, Ying
    Wen, Lei
    Zhang, Chensheng
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Zhang, Junping
    Synergistic effects of gelatin and convection on copper foil electrodeposition2016Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 211, s. 245-254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Copper foil electrodeposition has been explored using a pure titanium rotating disk electrode (RDE) in acidic electrolytes containing gelatin and/or chloride ions under different convection conditions. In the plating bath without gelatin, the results indicate that stronger convection promotes hydrogen evolution, which reduces the current efficiency during copper plating. Gelatin restrains the growth of copper grains in the lateral direction parallel to the surface. This results in grain refinement on the shiny side, an increase in local grain misorientation and in internal stresses on both the shiny and the matte side, and a reduction in their internal stress difference. At strong convection conditions and with gelatin present, copper deposits as strip-like grains along the centrifugal direction of the cross section, and finally forms a spiral-shaped pattern on the matte side. The causes of these features are discussed in detail. The combined influences of hydrogen and gelatin adsorption are further elaborated in a model for a copper deposition. The current investigation suggests that a moderate convection (somewhat lower than 1000 rpm) and a concentration of 2 ppm gelatin in the plating bath are sufficient for copper foil fabrication in the presence of chloride ions (20 ppm).

  • 13. Chen, H.
    et al.
    Gao, Y.
    Lu, Z.
    Ye, L.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, DUT-KTH Joint Education and Research Center on Molecular Devices, Dalian University of Technology (DUT), Dalian 116024, China.
    Copper Oxide Film In-situ Electrodeposited from Cu(II) Complex as Highly Efficient Catalyst for Water Oxidation2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 230, s. 501-507Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water splitting is deemed as an effective pathway for producing ideal clean energy, such as hydrogen. Here, a copper oxide film (Cu-Tris film) was prepared in-situ from a 0.2 M phosphate buffer solution (pH = 12.0) containing 1.0 mM Cu2+ and 2.0 mM Tris via controlled-potential electrodeposition. The Cu-Tris film showed a significantly low overpotential of 390 mV at a current density of 1.0 mA/cm2 for electrocatalytic water oxidation. Simultaneously, a considerably low Tafel slope of 41 mV/decade was achieved. This Cu-Tris film also exhibited a high and stable current density of ca. 7.5 mA/cm2 at 1.15 V vs. NHE for long-term electrocatalysis (10 h). These results demonstrated the superior performance of the developed Cu-Tris film, which should be attributed to the regulating effect of the five coordinated planar structure of the Cu-Tris complex precursor during the process of electrodeposition.

  • 14.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Håkansson, Bo
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Ruthenium based DSA in chlorate electrolysis–critical anode potential and reaction kinetics2003Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, nr 5, s. 473-481Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ruthenium based DSA®s have been investigated in chlorate electrolyte using rotating discs made from commercial electrodes. Measurements of the voltammetric charge, q*, and of iR-corrected polarisation curves up to current densities of 40 kA/m2 were recorded on new anodes and on aged anodes from 3 years of production in a chlorate plant. Anodic polarisation curves in chloride containing electrolytes bend towards a higher slope at approximately 1.2 V versus Ag/AgCl, likely due to oxidation of ruthenium. The potential and current density at which the curves bend have been defined as the critical potential, Ecr, and the critical current density, icr. New anodes that operate at a relatively high potential, >Ecr, obtain an increase in real surface area and thereby a decrease in anode potential and in the selectivity for oxygen formation during the first months of operation. Experiments at constant ionic strength under chlorate process conditions showed that Ecr decreased with increasing chloride concentration with a factor of −0.09 V/log Cl, whereas icr increased with increasing chloride concentration. The chlorine evolution reaction was of the first order with respect to chloride concentration. A possible reaction mechanism for chlorine formation is suggested.

  • 15.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Simonsson, Daniel
    KTH, Tidigare Institutioner, Kemiteknik.
    The effect of addition of chromate on the hydrogen evolution reaction and on iron oxidation in hydroxide and chlorate solutions1992Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 37, nr 10, s. 1873-1881Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The addition of chromate to the electrolyte has been shown in previous papers to hinder almost completely the electroreduction of hypochlorite, while the hydrogen evolution reaction can still proceed on the cathode surface. The effect of chromate on the latter reaction has been studied with cyclic voltammetry and by measuring polarization curves for iron electrodes in both chlorate and hydroxide electrolyte. For the sake of comparison, the investigations have also included the effects on the gold electrode in hydroxide solution. The results showed that the kinetics is changed in a way that decreases the differences in electrocatalytic activity between different electrode materials. Also, the innermost layer of the chromium hydroxide film seems to be the most active part in the HER. The chromate also affects the oxidation of the iron surface. A practical result of this is that the activity for the HER on corroded iron in chlorate electrolyte depends on whether the electrolyte contained chromate during the period of corrosion. The activation becomes much smaller if chromate is present.

  • 16.
    Crespo, Gaston A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Recent Advances in Ion-selective membrane electrodes for in situ environmental water analysis2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 245, s. 1023-1034Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Ion-selective membrane electrodes (ISEs) have become very attractive sensing platforms for environmental water analysis. This review mainly presents recent advances in polymeric-based ISEs relevant to water research and primarily focused on alkali and alkali earth-metal cations, ammonium ions, halide anions and certain oxoanions involved in biogeochemical cycles (e.g. nutrients (NO2 −, NO3 −), carbon (HCO3 −/CO3 2−) and phosphorus (HPO4 2−/H2PO4 −)). Clearly, ISEs have the potential to be the icon of decentralized ion chemical information for water research as in the case of wearable ISE sensors. The modern development of robust ISEs (mainly in all-solid-state format) has allowed an easy implementation either into submersible or non-submersible probes that maintain, to an acceptable degree, the required analytical performance. Remarkable benefits, such as avoidance of sample contamination, sample preservation and determination of perturbations of chemical speciation, are significant to enhancing the fundamental knowledge of ongoing biogeochemical process. A perspective on the current requirements of ISEs in terms of analytical performance and engineering construction is provided initially and is followed by recent contributions listed according to the sampling methodology, including i) on-board/on-site sampling with subsequent coverage of decentralized analysis (on moving or fixed platforms) and ii) in situ monitoring with submersible sensing probes. On the one hand, there is difficulty in making a general statement about ISEs for water research, specifically in terms of whether they are suitable. This lies in the complexity and heterogeneity of the samples. Accordingly, particular scenarios are discussed. On the other hand, it is also evident that further steps are still needed at the fundamental level, including development of receptors, robust membranes and novel alternatives that would enable the sensing of ions at deep-sea. Importantly, there is a plenty of room for improvement and new approaches; and it should be stressed that the recent progress in water research using ISEs has been owing to multidisciplinary efforts. Facing this challenge is very exciting and the development of ISE platforms that enable working in real conditions is quite plausible.

  • 17. Crespo, Gaston A.
    et al.
    Afshar, Majid Ghahraman
    Barrabes, Noelia
    Pawlak, Marcin
    Bakker, Eric
    Characterization of Salophen Co(III) Acetate Ionophore for Nitrite Recognition2015Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 179, s. 16-23Artikel i tidskrift (Refereegranskat)
  • 18. Cuartero, Maria
    et al.
    Acres, Robert G.
    Bradley, John
    Jarolimova, Zdenka
    Wang, Lu
    Bakker, Eric
    Crespo, Gaston A.
    University of Geneva, Switzerland.
    De Marco, Roland
    Electrochemical Mechanism of Ferrocene-Based Redox Molecules in Thin Film Membrane Electrodes2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 238, s. 357-367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cyclic voltammetry (CV) in chloride-based aqueous electrolytes of ferrocene molecule doped thin membranes (similar to 200 nm in thickness) on glassy carbon (GC) substrate electrodes, both plasticized poly (vinyl chloride) (PVC) and unplasticized poly(methyl methacrylate)/poly(decyl methacrylate) (PMMA-PDMA) membranes, has shown that the electrochemical oxidation behavior is irreversible due most likely to degradation of ferrocene at the buried interface (GC vertical bar membrane). Furthermore, CV of the ferrocene molecules at GC electrodes in organic solvents employing chloride-based and chloride-free organic electrolytes has demonstrated that the chloride anion is inextricably linked to this irreversible ferrocene oxidation electrochemistry. Accordingly, we have explored the electrochemical oxidation mechanism of ferrocene-based redox molecules in thin film plasticized and unplasticized polymeric membrane electrodes by coupling synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and near edge X-ray absorption fine structure (NEXAFS) with argon ion sputtering to depth profile the electrochemically oxidized thin membrane systems. With the PVC depth profiling studies, it was not possible to precisely study the influence of chloride on the ferrocene reactivity due to the high atomic ratio of chloride in the PVC membrane; however, the depth profiling results obtained with a chlorine-free polymer (PMMA-PDMA) provided irrefutable evidence for the formation of a chloride-based iron product at the GC| PMMA-PDMA interface. Finally, we have identified conditions that prevent the irreversible conversion of ferrocene by utilizing a high loading of redox active reagent and/or an ionic liquid (IL) membrane plasticizer with high ionicity that suppresses the mass transfer of chloride.

  • 19.
    Cuartero, Maria
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Chai, Lijun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Zhang, Biaobiao
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Organisk kemi.
    De Marco, Roland
    Univ Sunshine Coast, Fac Sci Hlth Educ & Engn, 90s Sippy Downs Dr, Sippy Downs, Qld 4556, Australia.;Univ Queensland, Sch Chem & Mol Biosci, Brisbane, Qld 4072, Australia.;Curtin Univ, Fuels & Energy Technol Inst, Perth, WA 6102, Australia..
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Ferrocene self assembled monolayer as a redox mediator for triggering ion transfer across nanometer-sized membranes2019Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 315, s. 84-93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modulation of ion-transfer processes across nanometer-sized voltammetry membranes by ferrocene-based self-assembled monolayer on regular glassy carbon electrode is herein demonstrated. The composition of the membrane is advantageously tuned to promote either cation or anion transfer: the presence of an exchangeable cation results in cation transfer, whereas a lipophilic salt induces anion transfer through the fulfilment of the electroneutrality of the system. When an anodic scan oxidizes ferrocene moieties in the monolayer, these are stabilized by the pairing of lipophilic anions present in the membrane. As a result, either, hydrophilic cations present in the membrane are expelled into the solution or anions enter from the solution generating hence reversible and voltammetric waves for these transfers. The use of a redox active monolayer rather than a conducting polymer film or a redox active compound into the membrane overcomes a number of drawbacks previously manifested by these systems. The confinement of the redox process in a thin film at the immediate vicinity of the membrane allows to avoid the need of elevated number of redox moieties to be sued in the membrane, therefore suppressing its acute leaching and being compatible with the incorporation of both cation and anion ionophores for the first time. In this sense, assisted transfer of lithium and chloride are shown as proof-of-concept. Here, the peak potential of the associated voltammetric waves shifts according to the Nernst equation, in analogy to potentiometric sensors. Analytical detection of lithium and chloride ions in real samples is additionally presented.

  • 20. Danielsson, Carl-Ola
    et al.
    Dahlkild, Anders
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Velin, Anna
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    A Model for the Enhanced Water Dissociation On Monopolar Membranes2009Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 11, s. 2983-2991Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A model for the enhanced water dissociation that takes place at the solution/membrane interface in electromembrane processes is presented. The mechanisms behind the enhanced water dissociation are poorly understood and therefore a semi-empirical approach is suggested. The enhanced water dissociation is introduced as a heterogeneous surface reaction similar to the well established Butler–Volmer law for electrode reactions. In the model there are two parameters that need to be determined through experiments. A 1D diffusion boundary layer problem is presented and solved in order to show that a sufficient rate of water dissociation can be obtained with the model. The advantage of the presented model is that it can easily be incorporated into simulations of electromembrane processes such as electrodialysis, electrodeionization and electropermutation. The influence of the enhanced water dissociation on these processes can then be studied.

  • 21. Darab, Mandi
    et al.
    Barnett, Alejandro Oyarce
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. SINTEF, Norway.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thomassen, Magnus Skinlo
    Sunde, Svein
    The Influence of Catalyst Layer Thickness on the Performance and Degradation of PEM Fuel Cell Cathodes with Constant Catalyst Loading2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 232, s. 505-516Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three catalytic layers containing Pt nanoparticles supported on high surface area carbon of different Pt loading but with the same total amount of platinum and therefore of different thickness were employed as cathode catalytic layers (CCLs) in a PEM fuel cell. The layers were subjected to a degradation protocol with an upper potential limit of 1.5 V. Upon exposure to the degradation protocol particle size increased, the electrochemical areas (ECAs) of the catalysts decreased, the catalytic layers became thinner, and the average pore size decreased, indicating both carbon and Pt corrosion. The relative decrease in the ECA was approximately the same for all three layers and was therefore approximately independent of CCL thickness. For all samples the reaction order with respect to oxygen was one half and the samples showed doubling of the slope of the potential vs. log current curve (dEld logi) at high current densities. This indicates that kinetics control the potential at low currents and kinetics and proton migration (ohmic drops in the catalytic layer) at high. However, the degradation protocol also introduced limitations due to oxygen diffusion in the agglomerates. This led to a quadrupling of the dEld logi-slope in 13% oxygen in the samples with the highest catalyst area per volume. For the sample with the lowest catalyst area per volume this slope increased by a factor of six in 13% oxygen, indicating that the local current density exceeded that required for the Tafel slope of the oxygen-reduction reaction (ORR) to double.

  • 22.
    Davoodi, Ali
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Norgren, S.
    Sapa Technology, Finspång.
    Integrated AFM and SECM for in situ studies of localized corrosion of Al alloys2007Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, nr 27, s. 7697-7705Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rolled 3xxx series Al alloys, e.g., EN AW-3003, are generally used as fin or tube material in heat exchangers for automobiles. With reducing fin thickness, maintaining fin material integrity is of increasing importance. This study aimed at exploring the differences in intrinsic corrosion properties between EN AW-3003 and a newly developed Al–Mn–Si–Zr fin alloy using state-of-the-art local probing techniques. Volta potential mapping of both alloys by scanning Kelvin probe force microscopy (SKPFM) indicates a cathodic behaviour of constituent intermetallic particles (>0.5 μm) relative to the alloy matrix. Compared to EN AW-3003, the Al–Mn–Si–Zr alloy has a smaller number of particles with large Volta potential difference relative to the matrix. In situ atomic force microscopy (AFM) measurements in slightly corrosive solutions showed extensive localized dissolution and deposition of corrosion products on EN AW-3003, and only a small number of corroding sites and “tunnel-like” pits on Al–Mn–Si–Zr. Probing the ongoing localized corrosion process by integrated AFM and scanning electrochemical microscopy (SECM) revealed more extensive local electrochemical activity on EN AW-3003 than on Al–Mn–Si–Zr. In all, the lower corrosion activity and smaller tunnel-like pits resulted in lower material loss of the Al–Mn–Si–Zr alloy, a beneficial property when striving towards thinner fin material.

  • 23.
    Diklic, Natasa P.
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Dobrota, Ana S.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Pasti, Igor
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mentus, Slavko, V
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia.;Serbian Acad Arts & Sci, Knez Mihajlova 35, Belgrade 11000, Serbia..
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Skorodumova, Natalia, V
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sodium storage via single epoxy group on graphene - The role of surface doping2019Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 297, s. 523-528Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to its unique physical and chemical properties, graphene is being considered as a promising material for energy conversion and storage applications. Introduction of functional groups and dopants on/in graphene is a useful strategy for tuning its properties. In order to fully exploit its potential, atomic-level understanding of its interaction with species of importance for such applications is required. We present a DFT study of the interaction of sodium atoms with epoxy-graphene and analyze how this interaction is affected upon doping with boron and nitrogen. We demonstrate how the dopants, combined with oxygen-containing groups alter the reactivity of graphene towards Na. Dopants act as attractors of epoxy groups, enhancing the sodium adsorption on doped oxygen-functionalized graphene when compared to the case of non-doped epoxy-graphene. Furthermore, by considering thermodynamics of the Na interaction with doped epoxy-graphene it has been concluded that such materials are good candidates for Na storage applications. Therefore, we suggest that controlled oxidation of doped carbon materials could lead to the development of advanced anode materials for rechargeable Na-ion batteries.

  • 24. Ding, Xin
    et al.
    Gao, Yan
    Fan, Ting
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ji, Yongfei
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhang, Linlin
    Yu, Ze
    Ahlquist, Mårten S. G.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi. Dalian University of Technology (DUT), China.
    Silicon Compound Decorated Photoanode for Performance Enhanced Visible Light Driven Water Splitting2016Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 215, s. 682-688Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An efficient dye (1) sensitized photoelectrochemical cell (DS-PEC) has been assembled with a silicon compound (3-chloropropyl) trimethoxy-silane (Si-Cl) decorated working electrode (WE) TiO2(1 + 2). The introduction of this Si-Cl molecule on photoanode leads to better performances on efficiency than untreated ones for light driven water splitting. The firm Si-O layer formed on TiO2 increased the resistance of the TiO2/catalyst interface which is assumed to decrease charge recombination from TiO2 to the oxidized catalyst 2. The work presented here provides an effective method to improve the performances of DS-PECs.

  • 25. Ding, Xin
    et al.
    Gao, Yan
    Zhang, Linlin
    Yu, Ze
    Liu, Jianhui
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Artificial photosynthesis: A two-electrode photoelectrochemical cell for light driven water oxidation with molecular components2014Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 149, s. 337-340Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An efficient two-electrode molecular PEC was assembled, in which a photoanode was constructed using a co-adsorbed method with a molecular photosensitizer (PS) 1 and a molecular catalyst 2 on TiO2-sintered FTO electrode (TiO2(1 + 2)). Without applied bias against a reference electrode, the system achieves remarkable photocurrent densities and carries out light driven water oxidation as evidenced by Clark electrode measurements in solution. A photocurrent density of 70 mA/cm(2) has been obtained within 10 s illumination time, and a TON of about 220 was obtained with a maximum turnover frequency (TOF) of ca. 4 min(-1) within the initial 5 minutes illumination duration.

  • 26. Dobrota, Ana S.
    et al.
    Pasti, Igor A.
    Mentus, Slavko V.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Uppsala University, Sweden.
    Skorodumova, Natalia V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Uppsala University, Sweden.
    Functionalized graphene for sodium battery applications: the DFT insights2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 250, s. 185-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Considering the increasing interest in the use of graphene-based materials for energy conversion and storage applications, we have performed a DFT study of Na interaction with doped graphene, both in non-oxidized and oxidized forms. Oxidation seems to play the crucial role when it comes to the interaction of doped graphene materials with sodium. The dopants act as attractors of OH groups, making the material prone to oxidation, and therefore altering its affinity towards Na. In some cases, this can result in hydroxide or water formation - an irreversible change lethal for battery performance. Our results suggest that one should carefully control the oxidation level of doped graphene-based materials if they are to be used as sodium battery electrode materials as the optimal oxidation level depends on the dopant type.

  • 27. Dobrota, Ana S.
    et al.
    Pasti, Igor A.
    Skorodumova, Natalia V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Uppsala University, Sweden.
    Oxidized graphene as an electrode material for rechargeable metal-ion batteries - a DFT point of view2015Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 176, s. 1092-1099Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In line with a growing interest in the use of graphene-based materials for energy storage applications and active research in the field of rechargeable metal-ion batteries we have performed a DFT based computational study of alkali metal atoms (Li, Na and K) interaction with an oxidized graphene. The presence of oxygen surface groups (epoxy and hydroxyl) alters the chemisorption properties of graphene. In particular, we observe that the epoxy groups are redox active and enhance the alkali metal adsorption energies by a factor of 2 or more. When an alkali metal atom interacts with hydroxyl-graphene the formation of metal-hydroxide is observed. In addition to a potential boost of metal ion storage capability, oxygen functional groups also prevent the precipitation of the metal phase. By simulating lithiation/de-lithiation process on epoxy-graphenes, it was concluded that the oxidized graphene can undergo structural changes during battery operation. Our results suggest that the content and the type of oxygen surface groups should be carefully tailored to maximize the performance of metal-ion batteries. This is mainly related to the control of the oxidation level in order to provide enough active centers for metal ion storage while preserving sufficient electrical conductivity.

  • 28. Dolidze, T. D.
    et al.
    Khoshtariya, D. E.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Glaser, Julius
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Two-equivalent electrochemical reduction of a cyano-complex Tl-III(CN)(2) (+) and the novel di-nuclear compound (CN)(5)Pt-II-Tl-III (0)2005Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 50, nr 22, s. 4444-4450Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Extending our recent insights in two-electron transfer microscopic mechanisms for a Tl-III/Tl-I redox system, the electrochemical response of glassy carbon electrode in acidified solutions of Tl-III (ClO4)(3) containing different concentrations of sodium cyanide has been extensively studied for the first time by use of cyclic voltammetry and the CVSIM curve simulation PC program. The complex [Tl-III(CN)(2)](+) has been thoroughly identified electrochemically and shown to display a single welldefined reduction wave (which has no anodic counterpart), ascribed to the two-equivalent process yielding [Tl-I(aq)](+). This behavior is similar to that of [Tl-III (aq)](3+) ion in the absence of sodium cyanide, disclosed in the previous work, and is compatible with the quasi-simultaneous yet sequential two-electron transfer pattern (with two reduction waves merged in one), implying the rate-determining first electron transfer step (resulting in the formation of a covalently interacting di-thallium complex as a metastable intermediate), and the fast second electron transfer step. Some preliminary studies of the two-equivalent reduction of directly metal-metal bonded stable compound [(CN)(5)Pt-II-Tl-III](0) has been also performed displaying two reduction waves compatible with a true sequential pattern.

  • 29. 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 SOFC2016Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 193, s. 225-230Artikel i tidskrift (Refereegranskat)
    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.

  • 30. Ebin, B.
    et al.
    Gümen, S.
    Arslan, C.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical properties of nanocrystalline LiFe xMn 2-xO 4 (x = 0.2-1.0) cathode particles prepared by ultrasonic spray pyrolysis method2012Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 76, s. 368-374Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nanocrystalline LiFe xMn 2-xO 4 (x = 0.2-1.0) particles were prepared by ultrasonic spray pyrolysis method using nitrate salts of ingredients at 800°C in air atmosphere. Particle properties were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy. Besides, cyclic voltammetry and galvanostatic tests were performed to investigate the effects of the iron substituent amount on electrochemical behavior. Particle characterization studies show that nanocrystalline particles have spinel structure and they are in submicron size range with spherical morphology. The lowest iron doped sample (LiFe 0.2Mn 1.8O 4) exhibits 117 mAh g -1 cumulative discharge capacity at 0.5 C and 88% capacity retention for 4 V plateau after 50 cycles. At higher iron concentrations, substituent tends to occupy the 8a tetrahedral sites, which prevent the lithium transport in the lattice during charge-discharge process. Increasing of the iron amount in the spinel structure causes the deterioration of the electrochemical performance.

  • 31. Edwards, M. O. M.
    et al.
    Boschloo, Gerrit
    Gruszecki, T.
    Pettersson, H.
    Sohlberg, R.
    Hagfeldt, A.
    'Electric-paint displays' with carbon counter electrodes2001Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 46, nr 13-14, s. 2187-2193Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    'Electric-paint displays' are electrochromic displays with dyed nanostructured metal-oxide electrodes, e.g. viologen-derivatized nanostructured titanium dioxide electrodes. Such displays are particularly promising for applications with low switch frequency, large segment areas, and high demands on colours, background brightness, and large viewing-angles. The concept is simple and well suited for inexpensive industrial production methods. We present blue-on-white electric-paint displays with porous carbon counter electrodes. The initial results with laboratory prototypes are promising. The switch time is about 1/2 s and the reflectance in the bleached state is as high as 40-55% in the visible region. Furthermore, the display prototypes sustain more than 100 000 switching cycles without severe degradation. The results from spectroelectrochemical measurements on the assembled displays are presented.

  • 32.
    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 cell2007Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, nr 12, s. 4239-4245Artikel i tidskrift (Refereegranskat)
    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.

  • 33.
    Endrodi, Balazs
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. University of Szeged, Hungary.
    Simic, Nina
    Wildlock, Mats
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A review of chromium(VI) use in chlorate electrolysis: Functions, challenges and suggested alternatives2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 234, s. 108-122Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Sodium chlorate is industrially produced by electrolysis of an aqueous salt solution, in which chromium ( VI) constitutes an important excipient component. It is added to a concentration of a few grams Na2Cr2O7/ liter to the electrolyte and has several functions in the process, the most important being to increase the Faradaic efficiency for hydrogen evolution in the undivided electrochemical cells. A thin film of Cr(OH)(3) x nH(2)O formed by reductive deposition on the cathodes decreases the rate of unwanted side reactions, while still enabling hydrogen evolution to occur. In addition chromium(VI) buffers the electrolyte at the optimum pH for operation and promotes the desired homogeneous reactions in the electrolyte bulk. Chromium species also affect the rates of hydrogen and oxygen evolution at the electrodes and are said to protect the steel cathodes from corrosion. Although chromium(VI) stays in a closed loop during chlorate production, chromate is a highly toxic compound and new REACH legislation therefore intends to phase out its use in Europe from 2017. A production without chromium(VI), with no other process modifications is not possible, and today there are no commercially available alternatives to its addition. Thus, there is an urgent need for European chlorate producers to find solutions to this problem. It is expected that chromium-free production will be a requirement also in other parts of the world, following the European example. As the chromium(VI) addition affects the chlorate process in many ways its replacement might require a combination of solutions targeting each function separately. The aim of this paper is to explain the role and importance of chromium(VI) in the chlorate manufacturing process. Previous achievements in its replacement are summarized and critically evaluated to expose the current state of the field, and to highlight the most promising avenues to be followed. An attempt is also made to reveal connections with other research fields (e.g. photochemical water splitting, corrosion science) facing similar problems. Allied effort of these different communities is expected to open up research avenues to the mutual benefit of these fields.

  • 34.
    Endrődi, Balázs
    et al.
    University of Szeged, Hungary.
    Kormányos, A.
    Janáky, C.
    Berkesi, O.
    Visy, C.
    Fixation of laccase enzyme into polypyrrole, assisted by chemical interaction with modified magnetite nanoparticles: A facile route to synthesize stable electroactive bionanocomposite catalysts2014Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 122, s. 282-288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effective bio-electrocatalysts require stable immobilization of sufficient amounts of the bioactive component. In this study, a novel and efficient method for specific binding of laccase enzyme onto magnetite nanoparticles (NPs) is presented. The interaction between the chemically modified magnetite NPs and the enzyme was evidenced by both infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Subsequently, the enzyme-coated magnetite NPs were successfully incorporated into polypyrrole (PPy) matrix during galvanostatic electropolymerization. The encapsulation of laccase covered NPs was proved by EQCN, TEM, and FT-IR spectroscopy; whereas the electrochemical behaviour of the formed bionanocomposite was characterized by cyclic voltammetiy. In oxygen saturated solution a cathodic charge surplus was observed, related to the electrochemical reduction of oxygen. This surplus was two times higher in the case of the laccase containing layer compared to its only magnetite containing counterpart. Kinetic aspects of the oxygen reduction reaction (ORR) on the laccase containing films were investigated by hydrodynamic voltammetry, and the four-electron route was found to be exclusive, which is promising from the fuel cell perspective. Such synergistic combination of inorganic NPs and enzymes may open new avenues in the application of these bio-nanocomposite materials.

  • 35.
    Fontes, Eduardo
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Lagergren, Carina
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Simonsson, Daniel
    KTH, Tidigare Institutioner                               , Kemiteknik.
    MATHEMATICAL-MODELING OF THE MCFC CATHODE1993Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 38, nr 18, s. 2669-2682Artikel i tidskrift (Refereegranskat)
  • 36.
    Ge, Xinlei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Wang, Xidong
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Copper extraction from copper ore by electro-reduction in molten CaCl2-NaCl2009Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 18, s. 4397-4402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sintered solid porous pellets of copper sulfide (Cu2S) and Cu2S/FeS were electrolysed at a cell voltage of 2.2-2.8 V to elemental Cu, S and Cu, Fe, S, respectively in molten CaCl2-NaCl at 800 degrees C under the protection of argon gas. The process parameters for optimal electrolysis are presented. The electrolysis products are characterized by microscopic techniques and XRD. The product characteristics are linked to the process parameters. The direct electrolysis of the sulfide to copper with the emission of elemental sulphur offers an attractive green process route for the treatment of copper ore.

  • 37. Georen, P.
    et al.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Characterisation and modelling of the transport properties in lithium battery polymer electrolytes2001Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, nr 4, s. 577-587Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ionic transport properties of solid polymer electrolytes can limit the performance of lithium batteries and are difficult to characterise. Few characterisation methods are available and the reported results show large discrepancies and the methods do not take variations of the properties with salt concentration into account although such are typical for polymer electrolytes. In this study, numerical macroscopic modelling, using the concentrated solution theory, was employed to determine the transport properties and thermodynamic activity factor, allowing concentration-dependent parameters. A copolymer of ethylene oxide and propylene oxide with 0.11 - 2 M LiTFSI was characterised at 25 degreesC using chronopotentiometry and concentration cell experiments. The determined ionic conductivity, kappa, apparent salt diffusion coefficient, D-s and cationic transport number, t(+)(0), were in line with previous results and kappa was also verified using electrochemical impedance spectroscopy. t(+)(0) values below 0.25 were measured, showing a decrease with increasing salt concentration. It was found that it was important to take into account the concentration dependence of the transport properties as well as the ionic interaction and the activity factor of the salt. The study resulted in a transport model well suited for the system that can easily be used to simulate the electrolyte behaviour for any current.

  • 38.
    Georen, Peter
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Characterisation and modelling of the transport properties in lithium battery gel electrolytes - Part I. The binary electrolyte PC/LiClO42004Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 49, nr 21, s. 3497-3505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no full characterisation or modelling study could be found in the literature. In this paper, which is the first part of a study of the transport in the ternary gel system PMMA/PC/LiClO4, the liquid electrolyte PC/LiClO4 is characterised and modelled for concentrations between 0.1 and 2 M according to a previously employed methodology, based on electrochemical measurements. A model using concentration dependent interaction parameters proved to describe the results in the whole concentration region well. The cationic transport number and salt diffusivity were determined to be approximately 0.3 and 1e-10m(2)/s, respectively. The mean ionic activity factor variations prove to be substantial. Furthermore, it was demonstrated that the inter-ionic friction was important to consider at concentrations above 1 M. The fundamental friction parameters determined in this part will be used in the following part of the study to describe the friction between ions and solvent.

  • 39.
    Gil, Harveth
    et al.
    Department of Materials, University of Antioquia.
    Echavarria, Alejandro
    Department of Materials, University of Antioquia.
    Echeverria, Felix
    Department of Materials, University of Antioquia.
    Electrochemical reduction modeling of copper oxides obtained during in situ and ex situ conditions in the presence of acetic acid2009Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 20, s. 4676-4681Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used the potentiodynamic reduction technique to study the mechanism of copper oxide formation inthe presence of acetic acid.We performed all reductions under neutral conditions (0.1MKCl) until hydrogenevolution. We produced the copper oxides in an environment containing 0, 500, and 800 ppb aceticacid at high relative humidity. We then compared experimental results between electrochemically producedoxide films obtained by imposing anodic potentials to copper specimens in several concentrationsof pure acetic acid (1, 0.1, 0.01 and 0.001 M). We found that, as the concentration of the acid decreases,the formation of the copper oxide (I) increases.We also found the same peaks in samples produced underthe synthetic environment.We modeled the curves, taking into account the electrochemical reduction ofcopper (II) oxide (CuO), amorphous cuprite (Cu2O)am, intermediate cuprite (Cu2O)in, crystalline cuprite(Cu2O)cr, and hydrogen. These oxides have been previously detected in similar conditions. We found noevidence of copper carboxylate founding samples produced by the electrochemical method.

  • 40.
    Gode, Peter
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Jaouen, Frederic
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Lundblad, Anders
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Sundholm, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Influence of the composition on the structure and electrochemical characteristics of the PEFC cathode2003Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, nr 28, s. 4175-4187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence the composition of the cathode has on its structure and electrochemical performance was investigated for a Nafion content spanning from 10 to 70 wt.%. The cathodes were formed on a Nafion membrane by the spray method and using 20 wt.% Pt on Vulcan (E-TEK). Materials characterisation (SEM, STEM, gas and mercury porosimetry, electron conductivity) and electrochemical characterisation (steady-state polarisation curve, impedance spectroscopy in O-2 and current-pulse measurements in N-2) were performed. The impedance spectra were analysed using our dynamic agglomerate model. The results indicate that the agglomerate model is valid until a Nafion content of about 45 wt.%. Pt/C and Nation are homogeneously mixed for any composition and no Nafion film was observed. The cathodes containing 36-43 wt.% Nation display a single or double Tafel slope behaviour ascribed to diffusion limitations in the agglomerates. At larger Nation content, the agglomerate model can describe the curves only by assuming a diffusion coefficient 3-4 decades smaller than that of gases. At such compositions, the porosity was only 10%. These results were interpreted as a blocking of the pores and a non-percolating pore system for too large Nafion contents.

  • 41.
    Hallberg, Fredrik
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Vernersson, Thomas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Thyboll Pettersson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Dvinskikh, Sergey V.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Furo, Istvan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Fysikalisk kemi.
    Electrokinetic transport of water and methanol in Nafion membranes as observed by NMR spectroscopy2010Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, nr 10, s. 3542-3549Artikel i tidskrift (Refereegranskat)
    Abstract [en]
    Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nation 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant. (C) 2010 Elsevier Ltd. All rights reserved.
  • 42.
    He, Yunjuan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Faculty of Computer and Information, Hubei University, Wuhan, Hubei, China.
    Fan, Liangdong
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Faculty of Computer and Information, Hubei University, Wuhan, Hubei, China.
    Afzal, Muhammad
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Singh, Manish
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Zhang, Wei
    Zhao, Yufeng
    Li, Junjiao
    Zhu, Bin
    Faculty of Computer and Information, Hubei University, Wuhan, Hubei, China.
    Cobalt oxides coated commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta as high performance cathode for low-temperature SOFCs2016Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 191, s. 223-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to improve the catalytic activity of commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) for low-temperature solid oxide fuel cells (LTSOFC) (300-600 degrees C), CoOx has been used to modify the commercial BSCF through a solution coating approach. Phase and morphology of samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive spectrometry (EDS), respectively. BSCF with 10 wt% CoOx exhibited an improved conductivity of 44 S/cm, and achieved a peak power density of 463 mW/cm(2) at 550 degrees C for LTSOFC, which is a 100% enhancement than that with the BSCF cathode. The cathode oxygen reduction reaction (ORR) promoted by CoOx and enhanced device performance mechanism have been proposed. This work provides a new way for the exploitation of high effective cathode materials for LTSOFCs.

  • 43.
    Hedberg, Yolanda S.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Karolinska Inst, Sweden.
    Pradhan, Sulena
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Cappellini, F.
    Karlsson, Maria-Elisa
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst Sweden, Sweden.
    Karlsson, H. L.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Hedberg, Jonas F.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Electrochemical surface oxide characteristics of metal nanoparticles (Mn, Cu and Al) and the relation to toxicity2016Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 212, s. 360-371Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most metal nanoparticles (NPs), except noble metal NPs, rapidly form a thin surface oxide in ambient conditions. The protective properties of these oxides improve or worsen depending on the environment, e.g., the human lung. Several properties, including the chemical/electrochemical stability and defect density, determine the capacity of these surface oxides to hinder the bulk metal from further oxidation (corrosion). The aim of this study was to investigate whether electrochemical surface oxide characterization of non-functionalized base metal NPs of different characteristics (Al, Mn and Cu) can assist in understanding their bioaccessibility (metal release) in cell media (DMEM+) and their cytotoxic properties following exposure in lung epithelial (A549) cells. The composition and valence states of surface oxides of metal NPs and their electrochemical activity were investigated using an electrochemical technique based on a graphite paste electrode to perform cyclic voltammetry in buffer solutions and open circuit potential measurements in DMEM+. The electrochemical surface oxide characterization was complemented and verified by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The open circuit potential trends in DMEM+ correlated well with metal release results in the same solution, and provided information on the kinetics of oxide dissolution in the case of Cu NPs. Extensive particle agglomeration in cell medium (DMEM+) was observed by means of photon-cross correlation spectroscopy for all metal NPs, with sedimentation taking place very quickly. As a consequence, measurements of the real dose of added non-functionalized metal NPs to cell cultures for cytotoxicity testing from a sonicated stock solution were shown necessary. The cytotoxic response was found to be strongly correlated to changes in physico-chemical and electrochemical properties of the surface oxides of the metal NPs, the most potent being Cu NPs, followed by Mn NPs. No cytotoxicity was observed for Al NPs. The electrochemical surface oxide characterization corresponded well with other tools commonly used for nanotoxicological characterization and provided additional information.

  • 44. Hjelm, A. K.
    et al.
    Eriksson, T.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Electrochemical investigation of LiMn2O4 cathodes in gel electrolyte at various temperatures2002Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, nr 2, s. 171-179Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A composite lithium battery electrode of LiMn2O4 in combination with a gel electrolyte (1 M LiBF4/24 wt% PMMA/1:1 EC:DEC) has been investigated by galvanostatic cycling experiments and electrochemical impedance spectroscopy (EIS) at various temperatures, i.e. -3 < T < 56 degreesC, For analysis of EIS data, a mathematical model taking into account local kinetics and potential distribution in the liquid phase within the porous electrode structure was used. Reasonable values of the double-layer capacitance, the exchange-current density and the solid phase diffusion were found as a function of temperature. The apparent activation energy of the charge-transfer ( similar to 65 kJ mol(-1)), the solid phase transfer ( similar to 45 kJ mol(-1)) and of the ionic bulk and effective conductance in the gel phase ( similar to 34 kJ mol(-1)), respectively, were also determined, The kinetic results related to ambient temperature were compared to those obtained in the corresponding liquid electrolyte. The incorporated PMMA was found to reduce the ionic conductivity of the free electrolyte, and it was concluded that the presence of 24 wt% PMMA does not have a significant influence on the kinetic properties of LiMn2O4.

  • 45. Hjelm, A. K.
    et al.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Experimental and theoretical analysis of LiMn2O4 cathodes for use in rechargeable lithium batteries by electrochemical impedance spectroscopy (EIS)2002Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 47, nr 11, s. 1747-1759Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comparative study of the impedance response measured with composite electrodes and thin film electrodes of LiMn2O4 was conducted. The electrodes were prepared on different current collectors (i.e. aluminium, carbonised aluminium and gold) and the experiments were run at various state-of-discharge (SOD) and liquid electrolyte compositions. The impedance response was shown to be strongly dependent on the current collector used. It was demonstrated that the high-to-medium frequency semicircle can be attributed to the contact resistance between the current collector and the active electrode material and that the medium-to-low frequency semicircle can be ascribed to the active electrode material. For the analysis, a mathematical model based on a resistance between the current collector and the active electrode material, interfacial-charge transfer coupled to the double-layer charging and solid-phase diffusion was developed. Potential distribution due to porous electrode effects was also considered, Fitting the model to experimental data enabled reasonable values of the exchange-current density, the double-layer capacitance and the solid-phase diffusion coefficient. However, the very low fitted value of the effective conductivity in the liquid phase indicates that this model does not give a satisfying description of the intercalation process of LiMn2O4.

  • 46. Ihonen, J.
    et al.
    Jaouen, F.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Sundholm, G.
    A novel polymer electrolyte fuel cell for laboratory investigations and in-situ contact resistance measurements2001Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 46, nr 19, s. 2899-2911Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel polymer electrolyte membrane fuel cell and assembly was developed for laboratory investigations. In this cell a simultaneous measurement of clamping pressure and contact resistances is possible. In the study presented this paper, the cell was utilised in in-situ contact resistance measurements of unplated and plated stainless steel (type 316). These contact resistances were studied in situ as a function of time, clamping pressure, gas pressure and current density. Ex-situ measurements were used to validate the in-situ contact resistance measurements. The validity and error sources of the applied in-situ measurement method were studied using both computer simulations and experiments.

  • 47.
    Karacic, Dalibor
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Korac, Selma
    Univ Sarajevo, Fac Sci, Dept Chem, Zmaja Bosne 33-35, Sarajevo 71000, Bosnia & Herceg..
    Dobrota, Ana S.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Pasti, Igor A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Skorodumova, Natalia, V
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gutic, Sanjin J.
    Univ Sarajevo, Fac Sci, Dept Chem, Zmaja Bosne 33-35, Sarajevo 71000, Bosnia & Herceg..
    When supporting electrolyte matters - Tuning capacitive response of graphene oxide via electrochemical reduction in alkali and alkaline earth metal chlorides2019Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 297, s. 112-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ability to tune charge storage properties of graphene oxide ( GO) is of utmost importance for energy conversion applications. Here we show that the electrochemical reduction of GO is highly sensitive to the cations present in the solution. GO is reduced at more negative potential in alkali metal chloride solutions than in alkaline earth metal chlorides. During the reduction, the capacitance of GO increases from 10 to 70 times. The maximum capacitances of reduced GO are between 65 and 130 F g(-1), depending on the electrolyte and the presence of conductive additive. We propose that different interactions of cations with oxygen functional groups of GO during the reduction are responsible for the observed effect. This hypothesis has been confirmed by Density Functional Theory calculations of alkali and alkaline earth metals interactions with epoxy-functionalized graphene sheet.

  • 48.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, Lars G. M.
    The electrocatalytic properties of doped TiO22015Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 180, s. 514-527Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To rationally control the catalytic properties of heterogeneous catalysts is the goal in heterogeneous (electro)catalysis research. Recent developments of theoretical methods based on density functional theory have enabled computational screening of catalysts, to achieve fundamental understanding of which catalyst is optimal for a certain reaction. In the present work, such screening is employed to elucidate the electrocatalytic properties of doped rutile TiO2. Electrodes based on this material are widely used in industrial production of, e.g., chlorine and sodium chlorate. The screening covers 38 different dopants, including all fourth, fifth and sixth row transition metals. Several dopants are predicted to activate TiO2, resulting in a material optimal either for the oxygen evolution reaction, or for selective chlorine evolution. The results can serve as a map for the rational design of electrocatalysts based on TiO2.

  • 49.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hansen, Heine A.
    Bligaard, Thomas
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, Lars G. M.
    Ti atoms in Ru0.3Ti0.7O2 mixed oxides form active and selective sites for electrochemical chlorine evolution2014Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 146, s. 733-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrocatalytic properties of the (1 1 0) surface of Ru-doped TiO2, Ti-doped RuO2 and the industrially important Dimensionally Stable Anode (DSA) composition Ru0.3Ti0.7O2 have been examined using density functional theory. It is found that the oxygen adsorption energy on a Ti site is strongly affected by the presence of small amounts of Ru dopant, whereas oxygen adsorption is relatively unaffected by Ti dopants in RuO2. The calculations also indicate that coordinatively unsaturated Ti sites on Ru-doped TiO2 and on Ru0.3Ti0.7O2 could form active and selective sites for Cl-2 evolution. These results suggest a reason for why DSA shows a higher chlorine selectivity than RuO2 and propose an experimental test of the hypothesis.

  • 50.
    Kiros, Yohannes
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Pirjamali, M.
    Bursell, Martin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk reaktionsteknik.
    Oxygen reduction electrodes for electrolysis in chlor-alkali cells2006Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, nr 16, s. 3346-3350Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oxygen reduction electrodes, containing non-noble metal catalysts supported on high surface area carbon and wet-proofed with PTFE were tested under reaction conditions for the chlor-alkali electrolysis. Double-layer gas diffusion electrodes were prepared by rolling of an active layer and diffusion layer on a nickel wire screen, compressed and sintered at 300 degrees C. Electrochemical measurements for substantiating the activity and stability of the half-cells were conducted in 8 M NaOH by supplying oxygen at a cell temperature of 70 degrees C and a constant current load of 300 mA cm(-2). An electrolysis cell with a dimensionally stable anode (DSA) and double-layered cathode was assembled, where 4.8 M NaCl and oxygen were supplied, respectively, for the production of chlorine and NaOH. The cell performances as well as stability of the electrodes were investigated at about 80 degrees C. This study shows that by replacing the high voltage consuming hydrogen-evolving reaction and by adopting highly active electrocatalysts as cathode materials, energy savings of more than 30% could be realized.

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