Change search
Refine search result
12 1 - 50 of 79
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Afzal, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Wang, Baoyuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhang, Wei
    He, Yunjuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Binzhu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, p. 136-142Article in journal (Refereed)
    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. Agrell, J.
    et al.
    Birgersson, H.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Steam reforming of methanol over a Cu/ZnO/Al2O3 catalyst: a kinetic analysis and strategies for suppression of CO formation2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 106, no 1-2, p. 249-257Conference paper (Refereed)
    Abstract [en]

    Steam reforming of methanol (CH3OH + H2O --> CO2 + 3H(2)) was studied over a commercial Cu/ZnO/Al2O3 catalyst for production of hydrogen onboard proton exchange membrane (PEM) fuel cell vehicles. A simple power-law rate expression was fitted to experimental data in order to predict the rates Of CO2 and H-2 formation under various reaction conditions. The apparent activation energy (E-a) was estimated to be 100.9 kJ mol(-1), in good agreement with values reported in the literature. Appreciable amounts of CO by-product were formed in the reforming process at low contact times and high methanol conversions. Being a catalyst poison that deactivates the electrocatalyst at the fuel cell anode at concentrations exceeding a few ppm, special attention was paid to the pathways for CO formation and strategies for its suppression. It was found that increasing the steam-methanol ratio effectively decreases CO formation. Likewise, addition of oxygen or air to the steam-methanol mixture minimises the production of CO. By shortening the contact time and lowering the maximum temperature in the reactor, CO production can be further decreased by suppressing the reverse water-gas shift reaction.

  • 3. Benamira, M.
    et al.
    Ringuede, A.
    Albin, V.
    Vannier, R. -N
    Hildebrandt, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Cassir, M.
    Gadolinia-doped ceria mixed with alkali carbonates for solid oxide fuel cell applications: I. A thermal, structural and morphological insight2011In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, no 13, p. 5546-5554Article in journal (Refereed)
    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.

  • 4.
    Birgersson, Erik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Faxén Laboratory.
    Vynnycky, Michael
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Faxén Laboratory.
    A quantitative study of the effect of flow-distributor geometry in the cathode of a PEM fuel cell2006In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 153, no 1, p. 76-88Article in journal (Refereed)
    Abstract [en]

    An isothermal three-dimensional model describing mass, momentum and species transfer in the cathode of a proton exchange membrane fuel cell has been used to study four different flow-distributors: interdigitated, coflow and counterflow channels, and a foam. A quantitative comparison of the results shows; that the interdigitated channels can sustain the highest current densities, followed in descending order by the foam, the counterflow and the coflow channels. The foam yields the most uniform current density distribution at higher currents, but care should be taken as to its permeability to avoid unreasonably high-pressure drops.

  • 5.
    Bodén, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Di, Jing
    School of Chemical Engineering and Technology, Tianjin University, China.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wang, Cheng Yang
    School of Chemical Engineering and Technology, Tianjin University, China.
    Conductivity of SDC and (Li/Na)2CO3 composite electrolytes in reducing and oxidising atmospheres2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 172, no 2, p. 520-529Article in journal (Refereed)
    Abstract [en]

    Composite electrolytes made of samarium-doped cerium oxide and a mixture of lithium carbonate and sodium carbonate salts are investigated with respect to their structure, morphology and ionic conductivity. The composite electrolytes are considered promising for use in so called intermediate temperature solid oxide fuel cells (IT-SOFC), operating at 400-600 degrees C. The electrolytes are tested in both gaseous anode (reducing) and cathode (oxidising) environments and at different humidities and carbon dioxide partial pressures. For the structure and morphology measurements, it was concluded that no changes occur to the materials after usage. From measurements of melting energies, it was concluded that the melting point of the carbonate salt phase decreases with decreasing fraction of carbonate salt and that a partial melting occurs before the bulk melting point of the salt is reached. For all the composites, two regions may be observed for the conductivity, one below the carbonate salt melting point and one above the melting point. The conductivity is higher when electrolytes are tested in anode gas than when tested in cathode gas, at least for electrolytes with less than half the volume fraction consisting of carbonate salt. The higher the content of carbonate salt phase, the higher the conductivity of the composite for the temperature region above the carbonate melting point. Below the melting point, though, the conductivity does not follow this trend. Calculations on activation energies for the conductivity show no trend or value that indicates a certain transport mechanism for ion transport, either when changing between the different composites or between different gas environments.

  • 6.
    Bodén, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Yoshikawa, Masahiro
    Central Research Institute of Electric Power Industry, Energy Engineering Research Laboratory, Kanagawa ,Japan.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    The solubility of Ni in molten Li2CO3–Na2CO3 (52/48) in H2/H2O/CO2 atmosphere2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 166, no 1, p. 59-63Article in journal (Refereed)
    Abstract [en]

    In this work the solubility of a Ni-Al anode for MCFC has been studied at atmospheric pressure and two different temperatures using various gas compositions containing H-2/H2O/CO2. It is well known that nickel is dissolved at cathode conditions in an MCFC. However, the results in this study show that nickel can be dissolved also at the anode, indicating that the solubility increases with increasing CO2 partial pressure of the inlet gas and decreasing with increasing temperature. This agrees with the results found by other authors concerning the solubility of NiO at cathode conditions. The dissolution of Ni into the melt can proceed in two ways, either by the reduction of water or by the reduction of carbon dioxide.

  • 7.
    Brown, Shelley
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    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, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites: I. Full Cell Results2008In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 185, no 2, p. 1444-1453Article in journal (Refereed)
    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.

  • 8.
    Brown, Shelley
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    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, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Cycle Life Evaluation of 3 Ah LixMn2O4-based Lithium-Ion Secondary Cells for Low-Earth-Orbit Satellites: II. Harvested Electrode Examination2008In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 185, no 2, p. 1454-1464Article in journal (Refereed)
    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.

  • 9.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Shanghai Institute of Technology, China.
    Ionic conductivity of dense BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) (Ln = Y, Sm, Gd, Dy) electrolytes2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 272, p. 786-793Article in journal (Refereed)
    Abstract [en]

    BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) (BZCLn532, Ln = Y, Sm, Gd, Dy) based electrolytes were successfully synthesized by a cost-effective solid-state reactive sintering (SSRS) method while using 1.0 wt.% NiO as a sintering aid. Dense pellets of BZCLn532 compounds can be prepared at sintering temperatures of 1600 degrees C (BZCY532) and 1400 degrees C (BZCS532, BZCG532 and BZCD532). The conductivities of the dense BZCLn532 ceramics were tested in dry and wet air at temperatures of 700 degrees C-200 degrees C. On the basis of the obtained results, it could be concluded that the BZCY532-based electrolyte show promise for use as oxygen-ion conductors and proton conductors in intermediate temperature solid oxide fuel cells (ITSOFCs).

  • 10.
    Bursell, Martin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    a sealed rechargeable metal-oxygen battery for traction purposes1980In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 8, p. 513-521Article in journal (Refereed)
    Abstract [en]

    A prototype of a sealed, rechargeable iron-oxygen battery that is based on a new oxygen electrode design is described, noting that the electrode design has made it possible to considerably simplify construction. It is pointed out that the oxygen electrode can be described as a self-breathing oxygen pocket electrode. It reaches 2 cm above the electrolyte in the battery and is fed with oxygen at the top of the battery by virtue of the pressure difference between the top of the electrode and the bottom.

  • 11. Ciosek Högström, Katarzyna
    et al.
    Lundgren, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wilken, Susanne
    Zavalis, Tommy G.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Edström, Kristina
    Jacobsson, Per
    Johansson, Patrik
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Impact of the flame retardant additive triphenyl phosphate (TPP) on the performance of graphite/LiFePO4 cells in high power applications2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 256, p. 430-439Article in journal (Refereed)
    Abstract [en]

    This study presents an extensive characterization of a standard Li-ion battery (LiB) electrolyte containing different concentrations of the flame retardant triphenyl phosphate (TPP) in the context of high power applications. Electrolyte characterization shows only a minor decrease in the electrolyte flammability for low TPP concentrations. The addition of TPP to the electrolyte leads to increased viscosity and decreased conductivity. The solvation of the lithium ion charge carriers seem to be directly affected by the TPP addition as evidenced by Raman spectroscopy and increased mass-transport resistivity. Graphite/LiFePO4 full cell tests show the energy efficiency to decrease with the addition of TPP. Specifically, diffusion resistivity is observed to be the main source of increased losses. Furthermore, TPP influences the interface chemistry on both the positive and the negative electrode. Higher concentrations of TPP lead to thicker interface layers on LiFePO4. Even though TPP is not electrochemically reduced on graphite, it does participate in SEI formation. TPP cannot be considered a suitable flame retardant for high power applications as there is only a minor impact of TPP on the flammability of the electrolyte for low concentrations of TPP, and a significant increase in polarization is observed for higher concentrations of TPP.

  • 12. Di, Jing
    et al.
    Chen, Mingming
    Wang, Chengyang
    Zheng, Jiaming
    Fan, Liangdong
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Samarium doped ceria-(Li/Na)(2)CO3 composite electrolyte and its electrochemical properties in low temperature solid oxide fuel cell2010In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, no 15, p. 4695-4699Article in journal (Refereed)
    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.

  • 13.
    Ekström, Henrik
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Fridholm, B.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Comparison of lumped diffusion models for voltage prediction of a lithium-ion battery cell during dynamic loads2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 402, p. 296-300Article in journal (Refereed)
    Abstract [en]

    Three different time-dependent lumped battery models are presented, using a limited set of only either three or four fitting parameters. The models all include one linear (resistive), one non-linear (kinetic) and one time-dependent element, the latter describing the diffusive processes in the battery. The voltage predictive capabilities of the models versus experimental dynamic load data for a plug-in hybrid vehicle battery are compared. It is shown that models based on a diffusion equation in an idealized particle perform similarly to a model based on an RC (resistive-capacitor) pair. In addition, by exchanging the RC element by a diffusion equation in an idealized particle it is also shown that it is possible to reduce the number of needed fitting parameters by one. 

  • 14. Escudero, M. J.
    et al.
    Hontanon, E.
    Schwartz, S.
    Boutonnet, Magali
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Daza, L.
    Development and performance characterisation of new electrocatalysts for PEMFC2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 106, no 1-2, p. 206-214Conference paper (Refereed)
    Abstract [en]

    New electrocatalysts based on Pt, Pt-Ru and Pt-Pd have been prepared by the microemulsion method. This method allows the production of a very narrow size distribution of metal particles, with an average size smaller than that of conventional electrocatalysts prepared by impregnation. Eight membrane electrode assemblies (MEAs) with an active surface area of 50 cm(2) were characterised in a single fuel cell. The MEAs consist of Nation 117 as membrane and a commercial electrocatalyst (40% Pt/C from E-TEK) on the cathode side, Four MEAs have electrocatalysts prepared by the microemulsion technique and the other four have commercial electrocatalysts on the anode side. The performance of the eight MEAs was evaluated by measuring the fuel cell polarisation curves and the internal resistance with H-2/O-2 and H-2/air, at 60 T and pressure in the range from I to 3 bar. The MEAs with the electrocatalysts prepared by microemulsion showed a performance comparable to that of the MEAs with commercial electrocatalysts. The satisfactory results obtained show that microemulsion is a promising method for the preparation of electrocatalysts for fuel cells. Further effort will be devoted to the optimisation of the method, mainly, the deposition of the metal particles on the carbon support, which it is expected to enhance the fuel cell performance.

  • 15.
    Fan, Liangdong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wang, Chengyang
    Chen, Mingming
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Recent development of ceria-based (nano)composite materials for low temperature ceramic fuel cells and electrolyte-free fuel cells2013In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 234, p. 154-174Article, review/survey (Refereed)
    Abstract [en]

    In the last ten years, the research of solid oxide fuel cells (SOFCs) or ceramic fuel cells (CFC) had focused on reducing the working temperature through the development of novel materials, especially the high ionic conductive electrolyte materials. Many progresses on single-phase electrolyte materials with the enhanced ionic conductivity have been made, but they are still far from the criteria of commercialization. The studies of ceria oxide based composite electrolytes give an alternative solution to these problems because of their impressive ionic conductivities and tunable ionic conduction behaviors. Significant advances in the understanding the ceria based composite material and construction of efficient fuel cell systems have been achieved within a short period. This report reviews recent developments of ceria-based composite from different aspects: materials, fundamentals, technologies, fabrication/construction parameters, electrochemistry and theoretical studies. Particular attention is given to ceria-carbonate (nano)composite, including its fuel cell performance, multi-ionic transport properties, advanced applications, corresponding electrode material and stability concerning. Besides, several novel fuel cell (FC) concepts like nanowire FC, all-nanocomposite FC and single-component/electrolyte-free fuel cell (SC-EFFC) are presented. This mini-review emphasizes the promise of ceria-based composites for advanced FC application and highlights the breakthrough of SC-EFFC research for high efficient energy conversion.

  • 16.
    Fan, Liangdong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wang, Chengyang
    Osamudiamen, Ose
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Singh, Manish
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Mixed ion and electron conductive composites for single component fuel cells: I. Effects of composition and pellet thickness2012In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 217, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Electrochemical performances of single component fuel cells (SCFCs) based on mixed ion and electron conductors have been studied as a function of composition and pellet thickness by polarization curves and electrochemical impedance spectroscopy. The electronic conductor of LNCZO shows conductivities of 21.7 and 5.3 S cm(-1) in H-2 and in air, respectively. SCFC using 40 wt. % of LNCZO and 60 wt. % of ion conductive SDC-Na2CO3 with a thickness of 1.10 mm shows the highest power density of 0.35 W cm(-2) at 550 degrees C. The performance is correlated to the mixed conduction properties (ionic and electronic, p and n-type) and the microstructure of the functional SCFC layer.

  • 17.
    Fan, Liangdong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Chen, Mingming
    Chemical engineering and technology.
    Wang, Chengyang
    Chemical engineering and technology.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Qin, Haiying
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wang, Xuetao
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Wang, Xiaodi
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Ma, Ying
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    High performance transition metal oxide composite cathode for low temperature solid oxide fuel cells2012In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 203, no 1, p. 65-71Article in journal (Refereed)
    Abstract [en]

    Low temperature solid oxide fuel cells (SOFCs) with metal oxide composite cathode on the ceria–carbonate composite electrolyte have shown promising performance. However, the role of individual elements or compound is seldom investigated. We report here the effect of the ZnO on the physico-chemical and electrochemical properties of lithiated NiO cathode. The materials and single cells are characterized by X-ray diffraction, scanning electron microscopy, DC polarization electrical conductivity, electrochemical impedance spectroscopy and fuel cell performance. The ZnO modified lithiated NiO composite materials exhibit smaller particle size and lower electrical conductivity than lithiated NiO. However, improved electro-catalytic oxygen reduction activity and power output are achieved after the ZnO modification. A maximum power density of 808 mW cm−2 and the corresponding interfacial polarization resistance of 0.22 Ω cm2 are obtained at 550 °C using ZnO modified cathode and 300 μm thick composite electrolyte. The single cell keeps reasonable stability over 300 min at 500 °C. Thus, ZnO modified lithiated NiO is a promising cathode candidate for low temperature SOFCs.

  • 18.
    Folkesson, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Andersson, Christian
    Lund Univ, Dept Ind Elect Engn & Automat.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alaküla, Mats
    Lund Univ, Dept Ind Elect Engn & Automat.
    Overgaard, Lars
    Bus Chassis Pre Dev Dept, Scania.
    Real life testing of a hybrid PEM fuel cell bus2003In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 118, no 1-2, p. 349-357Article in journal (Refereed)
    Abstract [en]

    Fuel cells produce low quantities of local emissions, if any, and are therefore one of the most promising alternatives to internal combustion engines as the main power source in future vehicles. It is likely that urban buses will be among the first commercial applications for fuel cells in vehicles. This is due to the fact that urban buses are highly visible for the public, they contribute significantly to air pollution in urban areas, they have small limitations in weight and volume and fuelling is handled via a centralised infrastructure.

    Results and experiences from real life measurements of energy flows in a Scania Hybrid PEM Fuel Cell Concept Bus are presented in this paper. The tests consist of measurements during several standard duty cycles. The efficiency of the fuel cell system and of the complete vehicle are presented and discussed. The net efficiency of the fuel cell system was approximately 40% and the fuel consumption of the concept bus is between 42 and 48% lower compared to a standard Scania bus. Energy recovery by regenerative braking saves up 28% energy. Bus subsystems such as the pneumatic system for door opening, suspension and brakes, the hydraulic power steering, the 24 V grid, the water pump and the cooling fans consume approximately 7% of the energy in the fuel input or 17% of the net power output from the fuel cell system.

    The bus was built by a number of companies in a project partly financed by the European Commission's Joule programme. The comprehensive testing is partly financed by the Swedish programme "Den Grona Bilen" (The Green Car). A 50 kW(el) fuel cell system is the power source and a high voltage battery pack works as an energy buffer and power booster. The fuel, compressed hydrogen, is stored in two high-pressure stainless steel vessels mounted on the roof of the bus. The bus has a series hybrid electric driveline with wheel hub motors with a maximum power of 100 kW.

    Hybrid Fuel Cell Buses have a big potential, but there are still many issues to consider prior to full-scale commercialisation of the technology. These are related to durability, lifetime, costs, vehicle and system optimisation and subsystem design. A very important factor is to implement an automotive design policy in the design and construction of all components, both in the propulsion system as well as in the subsystems.

  • 19. Fu, Q. X.
    et al.
    Zha, S. W.
    Zhang, W.
    Peng, D. K.
    Meng, G. Y.
    Zhu, Bin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Intermediate temperature fuel cells based on doped ceria-LiCl-SrCl2 composite electrolyte2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 104, no 1, p. 73-78Article in journal (Refereed)
    Abstract [en]

    A new type of oxide-salt composite electrolyte, gadolinium-doped ceria (GDC)-LiCl-SrCl2, was developed and demonstrated its promising use for intermediate temperature (400-700 degreesC) fuel cells (ITFCs). The dc electrical conductivity of this composite electrolyte (0.09-0.13 S cm(-1) at 500-650 degreesC) was 3-10 times higher than that of the pure GDC electrolyte, indicating remarkable proton or oxygen ion conduction existing in the LiCl-SrCl2 chloride salts or at the interface between GDC and the chloride salts. Using this composite electrolyte, peak power densities of 260 and 510 mW cm(-2), with current densities of 650 and 1250 mA cm(-2) were achieved at 550 and 625 degreesC, respectively. This makes the new material a good candidate electrolyte for future low-cost ITFCs.

  • 20.
    Gao, Zhan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Liu, Xingmin
    Bergman, Bill
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Enhanced ionic conductivity of Ce0.8Sm0.2O2-delta by Sr addition2012In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 208, p. 225-231Article in journal (Refereed)
    Abstract [en]

    Sm and Sr co-doped ceria-based electrolyte with compositions of Ce-0.8(Sm1-xSrx)(0.2)O2-delta (x = 0, 0.3, 0.5, 0.7) are synthesized and investigated with the aim of improving the electrical properties of Ce0.8Sm0.2O2-delta. X-ray diffraction (XRD) and electron microscope (SEM and TEM) techniques are employed to characterize the microstructure of powders and sintered pellets. The ionic conductivity has been examined by the A.C. impedance spectroscopy in air. The Ce-0.8(Sm0.7Sr0.3)(0.2)O2-delta exhibits the highest bulk conductivity among the series, which can be mainly ascribed to the increase of oxygen vacancy concentration. The specific grain-boundary conductivities are observed to increase with the Sr doping content up to x = 0.5. Further increase in Sr concentration will lead to reduced specific grain-boundary conductivities. The total conductivities of all Sm and Sr co-doped ceria are higher than that of Ce0.8Sm0.2O1.9. The results indicate that Sr co-doping opens a new avenue to improve ionic conductivity in Ce0.8Sm0.2O1.9.

  • 21.
    Gao, Zhan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Liu, Xingmin
    Bergman, Bill
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Investigation of oxygen reduction reaction kinetics on Sm(0.5)Sr(0.5)CoO(3-delta) cathode supported on Ce(0.85)Sm(0.075)Nd(0.075)O(2-delta) electrolyte2011In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, no 22, p. 9195-9203Article in journal (Refereed)
    Abstract [en]

    Sm(0.5)Sr(0.5)CoO(3-delta) (SSC) cathode prepared by a glycine-nitrate process (GNP) is investigated for solid oxide fuel cells (SOFCs) based on Ce(0.85)Sm(0.075)Nd(0.075)O(2-delta) (SNDC) electrolyte. SSC forms cubic perovskite structure after being annealed at 1100 degrees C for 5 h. SSC cathode and SNDC electrolyte can retain their own structure and there is no reaction between the two compositions. The microstructure of the cathode and the interfaces between cathodes and SNDC electrolytes are studied by scanning electron microscopy (SEM) after sintering at various temperatures. Impedance spectroscopy measurements reveal that area specific resistances (ASRs) of SSC-SNDC30 cathode are much lower than those of SSC cathode. Kinetics of oxygen reduction reaction (ORR) on porous SSC cathode is investigated by analysis of impedance spectra. Medium-frequency conductivities show no dependency on oxygen partial pressure (Po(2)), which can be attributed to the oxygen ions transfer across the electrode/electrolyte interface. The dependencies of low-frequency conductivities on oxygen partial pressure (Po(2)) vary in the range from ca. 0.31 to ca. 0.34 and increase with the increasing temperatures. The low-frequency electrode process is a mixing process involving oxygen reduction reaction related to atomic oxygen and oxygen ions conduction step together with total charge-transfer step. IR-compensated current density (i)-overpotential (eta) relationship is established and the exchange current densities i(0) originated from high-field approximations are much higher than those of low-field approximations and a.c. impedance data under OCV state. It demonstrates the polarization overpotential has great effect on the kinetics of ORR. The polarization current is observed to increase with time in the long-term stability measurement, which can be ascribed to the propagation process of oxygen vacancies.

  • 22. Georen, P.
    et al.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    On the use of voltammetric methods to determine electrochemical stability limits for lithium battery electrolytes2003In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 124, no 1, p. 213-220Article in journal (Refereed)
    Abstract [en]

    In previous studies a novel amphiphilic co-polymer was developed for use in lithium-ion batteries. In order to evaluate the electrochemical stability of that electrolyte and compare it with others, a voltammetric method was applied on a set of electrolytes with different salts, solvents and polymers. However, initially the voltammetric methodology was studied. Platinum was found to be the most suited electrode material, experiencing no significant interfering reactions and a proper diffusion-controlled kinetic behaviour when sweep rate was varied. Furthermore, the influence on the voltammograms of adding water traces to the electrolytes was studied. It could be established that the oxidation peak around 3.8 V versus Li was related to water reactions. It was concluded that quantitative voltage values of the stability limits were difficult to assess using voltammetry. On the other hand, the method seemed well suited for comparison of electrolytes and to investigate the influences of electrolyte components on the stability. The voltammetric results varied little between the different electrolytes evaluated and the anodic and cathodic limits, as defined here, were in the range of I and 4.5 V vs. Li, respectively. Although the novel polymer did not affect the stability limit significantly it seemed to promote the breakdown reaction rate in all electrolytes tested. Furthermore, the use of LiTFSI salt reduced the stability window.

  • 23.
    Gustavsson, Marie
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Kasemo, Bengt
    Chalmers tekniska högskola, Göteborg.
    Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 163, no 2, p. 671-678Article in journal (Refereed)
    Abstract [en]

    Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.

  • 24.
    Haraldsson, Kristina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effects of Ambient Conditions on Fuel Cell Vehicle Performance2005In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 145, no 2, p. 298-306Article in journal (Refereed)
    Abstract [en]

    Ambient conditions have considerable impact on the performance of fuel cell hybrid vehicles. Here, the vehicle fuel consumption, the air compressor power demand, the water management system and the heat loads of a fuel cell hybrid sport utility vehicle (SUV) were studied. The simulation results show that the vehicle fuel consumption increases with 10% when the altitude increases from 0 m up to 3000 m to 4.1 L gasoline equivalents/100 km over the New European Drive Cycle (NEDC). The increase is 19% on the more power demanding highway US06 cycle. The air compressor is the major contributor to this fuel consumption increase. Its load-following strategy makes its power demand increase with increasing altitude. Almost 40% of the net power output of the fuel cell system is consumed by the air compressor at the altitude of 3000 m with this load-following strategy and is thus more apparent in the high-power US06 cycle.

    Changes in ambient air temperature and relative humidity effect on the fuel cell system performance in terms of the water management rather in vehicle fuel consumption. Ambient air temperature and relative humidity have some impact on the vehicle performance mostly seen in the heat and water management of the fuel cell system. While the heat loads of the fuel cell system components vary significantly with increasing ambient temperature, the relative humidity did not have a great impact on the water balance. Overall, dimensioning the compressor and other system components to meet the fuel cell system requirements at the minimum and maximum expected ambient temperatures, in this case 5 and 40 degrees C, and high altitude, while simultaneously choosing a correct control strategy are important parameters for efficient vehicle power train management.

  • 25.
    Haraldsson, Kristina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Folkesson, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Fuel Cell Buses in the Stockholm CUTE Project: First Experiences from a Climate Perspective2005In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 145, no 2, p. 620-631Article in journal (Refereed)
    Abstract [en]

    This paper aims to share the first experiences and results from the operation of fuel cell buses in Stockholm within the Clean Urban Transport for Europe (CUTE) project. The project encompasses implementation and evaluation of both a hydrogen fuel infrastructure and fuel cell vehicles in nine participating European cities. In total, 27 fuel cell buses, 3 in each city, are in revenue service for a period of 2 years.

    The availability of the fuel cell buses has been better than expected, about 85% and initially high fuel consumption has been reduced to approximately 2.2 kg H-2/10 km corresponding to 7.51 diesel equivalents/10 km. Although no major breakdowns have occurred so far, a few cold climate-related issues did arise during the winter months in Stockholm.

  • 26.
    Haraldsson, Kristina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Molin, Andreas
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Alvfors, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Cold Climate Thermal Management for Fuel Cells Using Phase Change MaterialsIn: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755Article in journal (Other academic)
  • 27.
    Haraldsson, Kristina
    et al.
    National Renewable Energy Laboratory, Golden, United States.
    Wipke, Keith
    National Renewable Energy Laboratory, Golden, United States.
    Evaluating PEM Fuel Cell System Models2004In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 126, no 1-2, p. 88-97Article in journal (Refereed)
    Abstract [en]

    Many proton exchange membrane (PEM) fuel cell models have been reported in publications and some are available commercially. This paper helps users match their modeling needs with specific fuel cell models. The paper has three parts. First, it describes the model selection criteria for choosing a fuel cell model. Second, it applies these criteria to select state-of-the-art fuel cell models available in the literature and commercially. The advantages and disadvantages of commercial models are discussed. Third, the paper illustrates the process of choosing a fuel cell model with an example: the National Renewable Energy Laboratory's (NREL's) evaluation of two detailed stand-alone fuel cell system models. One is from Virginia Tech University, and the other is from Sweden's Royal Institute of Technology. Both models have been integrated into NREL's vehicle simulation model ADVISOR(TM) 2003 (Advanced Vehicle Simulator).

  • 28.
    Hedström, Lars
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Wallmark, Cecilia
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Alvfors, Per
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rissanen, Markku
    Stridh, Bengt
    Ekman, Josefin
    Description and modelling of the solar–hydrogen–biogas-fuel cell system in GlashusEtt2004In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, no 131, p. 340-350Article in journal (Refereed)
    Abstract [en]

    The need to reduce pollutant emissions and utilise the world's available energy resources more efficiently has led to increased attention towards e.g. fuel cells, but also to other alternative energy solutions. In order to further understand and evaluate the prerequisites for sustainable and energy-saving systems, ABB and Fortum have equipped an environmental information centre, located in Hammarby Sjostad, Stockholm, Sweden, with an alternative energy system. The system is being used to demonstrate and evaluate how a system based on fuel cells and solar cells can function as a complement to existing electricity and heat production. The stationary energy system is situated on the top level of a three-floor glass building and is open to the public. The alternative energy system consists of a fuel cell system, a photovoltaic (PV) cell array, an electrolyser, hydrogen storage tanks, a biogas burner, dc/ac inverters, heat exchangers and an accumulator tank. The fuel cell system includes a reformer and a polymer electrolyte fuel cell (PEFC) with a maximum rated electrical output of 4 kW(el) and a maximum thermal output of 6.5 kW(th). The fuel cell stack can be operated with reformed biogas, or directly using hydrogen produced by the electrolyser. The cell stack in the electrolyser consists of proton exchange membrane (PEM) cells. To evaluate different automatic control strategies for the system, a simplified dynamic model has been developed in MATLAB Simulink. The model based on measurement data taken from the actual system. The evaluation is based on demand curves, investment costs, electricity prices and irradiation. Evaluation criteria included in the model are electrical and total efficiencies as well as economic parameters.

  • 29.
    Hellqvist Kjell, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Malmgren, Sara
    Ciosek, Katarzyna
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Edström, Kristina
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Comparing aging of graphite/LiFePO4 cells at 22 degrees C and 55 degrees C - Electrochemical and photoelectron spectroscopy studies2013In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 243, p. 290-298Article in journal (Refereed)
    Abstract [en]

    Accelerated aging at elevated temperature is commonly used to test lithium-ion battery lifetime, but the effect of an elevated temperature is still not well understood. If aging at elevated temperature would only be faster, but in all other respects equivalent to aging at ambient temperature, cells aged to end-of-life (EOL) at different temperatures would be very similar. The present study compares graphite/LiFePO4-based cells either cycle- or calendar-aged to EOL at 22 degrees C and 55 degrees C. Cells cycled at the two temperatures show differences in electrochemical impedance spectra as well as in X-ray photoelectron spectroscopy (XPS) spectra. These results show that lithium-ion cell aging is a complex set of processes. At elevated temperature, the aging is accelerated in process-specific ways. Furthermore, the XPS results of cycle-aged samples indicate increased deposition of oxygenated LiPF6 decomposition products in both the negative and positive electrode/electrolyte interfaces. The decomposition seems more pronounced at elevated temperature, and largely accelerated by cycling, which could contribute to the observed cell impedance increase.

  • 30. Hu, H.
    et al.
    Lin, Q.
    Muhammad, Afzal J.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Electrochemical study of lithiated transition metal oxide composite for single layer fuel cell2015In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 286, p. 388-393Article in journal (Refereed)
    Abstract [en]

    This study analyzed the effect of various semiconductors of transition metal oxides in modified lithiated NiO on the electrochemical performance of a single layer fuel cell (SLFC). A typical ionic conductor Ce0.8Sm0.2O2-δ (SDC) and three types of semiconductors Li0.3Ni0.6Cu0.07Sr0.03O2-δ (LNCuS), Li0.3Ni0.6Mn0.07Sr0.03O2-δ (LNMnS) and Li0.3Ni0.6Co0.07Sr0.03O2-δ (LNCoS), were the fundamental components of the SLFCs. The components were characterized by using X-ray diffraction (XRD), a scanning electron microscope (SEM), and an energy-dispersive X-ray spectrometer (EDS). The stability of the synthesized materials was evaluated using thermal gravity analysis (TGA). The ohmic resistances at 500 °C were 0.36, 0.48 and 0.58 Ω cm2 for 6SDC-4LNMnS, 6SDC-4LNCoS and 6SDC-4LNCuS, respectively. Among the three SLFCs, the single cell with 6SDC-4LNMnS achieves the highest power density (422 mW cm-2) but the lowest temperature stability, while the single cell with 6SDC-4LNCuS achieved the lowest power density (331 mW cm-2) but the highest temperature stability during the operation temperature.

  • 31. Hu, Huiqing
    et al.
    Lin, Qizhao
    Zhu, Zhigang
    Liu, Xiangrong
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Afzal, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    He, Yunjuan
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. Hubei Univ, Fac Phys & Elect Technol, Hubei Collaborat Innovat Ctr Adv Mat, Wuhan 430062, Hubei, Peoples R China.
    Effects of composition on the electrochemical property and cell performance of single layer fuel cell2015In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 275, p. 476-482Article in journal (Refereed)
    Abstract [en]

    In this study, the enhanced electrochemical performance of single layer fuel cells (SLFCs) based upon mixed ion and electron conductors is analyzed as a function of composition. We synthesize a series of Ce0.8Sm0.2O2-delta-Li0.3Ni0.6Cu0.07Sr0.03O2-delta (SDC-LNCS) with different weight ratios. The microstructure and morphology of the composite materials are characterized through X-ray diffraction (XRD), transmission electron microscope (TEM), and energy-dispersive X-ray spectrometer (EDS). Stability of the synthesized samples is evaluated by thermal gravity analysis (TGA). The SLFC with 6SDC-4LNCS exhibits a uniform distribution of the two compositions as well as demonstrates the highest power density of 312 mW cm-2 at 550 mu C. The performance is correlated to the balance of the conduction properties (ionic and electronic) of the functional SLFC layer. The results are a critical contribution to further development of this new energy transfer device.

  • 32. Hu, Huiqing
    et al.
    Lin, Qizhao
    Zhu, Zhigang
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Liu, Xianrong
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Fabrication of electrolyte-free fuel cell with Mg0.4Zn0.6O/Ce0.8Sm0.2O2-delta-Li0.3Ni0.6Cu0.07Sr0.03O2-delta layer2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 248, p. 577-581Article in journal (Refereed)
    Abstract [en]

    Electrolyte-free fuel cell (EFFC) which holds the similar function with the traditional solid oxide fuel cell (SOFC) but possesses a completely different structure, has draw much attention during these years. Herein, we report a complex of MZSDC LNCS (Mg0.4Zn0.6O/Ce0.8Sm0.2O2-delta-Li0.3Ni0.6Cu0.07Sr0.03O2-delta) for EFFC that demonstrates a high electrochemical power output of about 600 mW cm(-2) at 630 degrees C. The co-doped MZSDC is synthesized by a co-precipitation method. Semiconductor material of LNCS is synthesized by direct solid state reaction. The microstructure and morphology of the composite materials are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive Xray spectrometer (EDS). The performance of the cell with a large size (6 x 6 cm(2)) is comparable or even better than that of the conventional solid oxide fuel cells with large sizes. The maximum power output of 9.28 W is obtained from the large-size cell at 600 degrees C. This paper develops a new functional nanocomposite for EFFC which is conducive to its commercial use.

  • 33. Jalani, Nikhil H.
    et al.
    Ramani, Manikandan
    Ohlsson, Kristina
    KTH.
    Buelte, Steve
    Pacifico, Greg
    Pollard, Richard
    Staudt, Rhonda
    Datta, Ravindra
    Performance analysis and impedance spectral signatures of high temperature PBI-phosphoric acid gel membrane fuel cells2006In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, no 2, p. 1096-1103Article in journal (Refereed)
    Abstract [en]

    Polarization curves, i.e., dc performance, and impedance spectral signatures of polybenzimidazole (PBI)-phosphoric acid (H3PO4) membrane fuel cells are obtained in the temperature range of 160-180 degrees C, in an effort to investigate the effect of temperature, anode humidification, various cathode stoichs, and use of oxygen versus air. Thus, in situ electrochemical impedance spectroscopy (EIS) was used to obtain various resistances, ohmic as well as charge-transfer resistances, under these conditions. The results obtained show that PBI-H3PO4 gel membrane fuel cells exhibit very good performance in the temperature range of 160-180 degrees C with an ohmic resistance similar to Nation. Mass transfer limitations were determined by comparing performance polarization curves with air and oxygen along with EIS. Further EIS was also used to obtain signatures during fuel starvation, and electrical shorting across the cell.

  • 34.
    Jaouen, Frédéric
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Haasl, Sjoerd
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Lundblad, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Adhesive copper films for an air-breathing polymer electrolyte fuel cell2005In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 144, no 1, p. 113-121Article in journal (Refereed)
    Abstract [en]

    A design for an air-breathing and passive polymer electrolyte fuel cell is presented. Such a type of fuel cell is in general promising for portable electronics. In the present design, the anode current collector is made of a thin copper foil. The foil is provided with an adhesive and conductive coating, which firstly tightens the hydrogen compartment without mask or clamping pressure, and secondly secures a good electronic contact between the anode backing and the current collector. The cathode comprises a backing, a gold-plated stainless steel mesh and a current collector cut out from a printed circuit board. Three geometries for the cathode current collector were evaluated. Single cells with an active area of 2 cm(2) yielded a peak power of 250-300 MW cm(-2) with air and pure H-2 in a complete passive mode except for the controlled flow of H-2. The cells' response was investigated in steady state and transient modes.

  • 35.
    Ji, Yongfei
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Univ Sci & Technol China.
    Structure-dependent photocatalytic decomposition of formic acid on the anatase TiO2(101) surface and strategies to increase its reaction rate2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 306, p. 208-212Article in journal (Refereed)
    Abstract [en]

    Formic acid is a typical molecule that is involved in a lot important solar energy conversion processes. We perform first-principles calculations on the molecular mechanism of its photocatalytic decomposition reaction (PCD) on the anatase TiO2(101) surface. We find that the reaction barrier is sensitively dependent on the adsorption structure of the molecule. The one-step PCD of the monodentate formic acid has a lower barrier than that of bidentate formate. Coadsorbed water molecules can transform the formate from a bidentate to a monodentate configuration which greatly lower its decomposition barrier. Water molecule can also induce the spontaneous dissociation of the formic acid molecule. The monodentate dissociated formic acid is stabilized by the hydrogen bonds which will slightly enhance the barrier for its photodecomposition. However, the reaction rate can be further enhanced if the hydrogens are removed (for example, by oxygen molecules). Therefore, using coadsorbate and deliberately introducing and removing hydrogen bonds can be two strategies to tailor the photoreaction rate of the molecules.

  • 36.
    Kiros, Yohannes
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Schwartz, S.
    Long-term hydrogen oxidation catalysts in alkaline fuel cells2000In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 87, no 02-jan, p. 101-105Article in journal (Refereed)
    Abstract [en]

    Pt/Pd bimetallic combination and Raney Ni catalysts were employed in long-term electrochemical assessment of the hydrogen oxidation reaction (HOR) in 6 M KOH. Steady-state current vs. potential measurements of the gas diffusion electrodes have shown high activity for these types of catalysts. Durability tests of the electrodes have shown increased stability for the Pt/Pd-based catalysts than the Raney Ni at a constant load of 100 mA/cm(2) and at temperatures of 55 degrees C and 60 degrees C, respectively. Surface, structural and chemical analyses by BET surface area, transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) were used to characterize the composite electrode/catalyst both before and after the electrochemical testing.

  • 37. Kivisaari, T.
    et al.
    Bjornbom, P.
    Sylwan, Christopher
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Studies of biomass fuelled MCFC systems2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 104, no 1, p. 115-124Article in journal (Refereed)
    Abstract [en]

    In the present work, the methods, techniques and results obtained during the studies of biomass fuelled molten carbonate fuel cell (MCFC) systems within the Swedish national fuel cell program are presented. The power plants are 60 MW class, utilising biomass (i.e. wood chips) as the primary fuel. The biomass is converted via pressurised gasification into a gaseous form that, after subsequent cleaning, can be used in the fuel cells. An investigation of the effects of gasification pressure, temperature and the influence of internal reforming on the overall system performance is presented. All studies were carried out using the Aspen Plus(TM) with Model Manager(TM) simulation package.

  • 38.
    Kjellin, Per
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Palmqvist, Anders
    Chalmers tekniska högskola, Göteborg.
    On the activity and stability of Sr3NiPtO6 and Sr3CuPtO6 as electrocatalysts for the oxygen reduction reaction in a polymer electrolyte fuel cell2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 168, no 2, p. 346-350Article in journal (Refereed)
    Abstract [en]

    Sr3NiPtO6 and Sr3CUPtO6 were evaluated as low-platinum alternative oxygen reduction catalysts in a solid polymer electrolyte fuel cell at 80 degrees C. The oxides were synthesised using a new method based on an organometallic precursor route. The electrochemical evaluation showed similar oxygen reduction performance for Sr3NiPtO6 and Sr3CUPtO6, with a slightly higher activity for Sr3NiPtO6. In comparison with the oxides, the oxygen reduction activity for a commercial Pt/C catalyst was approximately 10 times higher. XRD analysis of the used electrodes revealed that the oxides were not stable in the PEMFC environment, and converted into platinum during operation. Elemental analysis of the used electrodes also showed a difference in platinum formation, where the platinum content on the surface of the electrode facing the gas diffusion layer was several times higher for Sr3NiPtO6 than Sr3CUPtO6. This indicates that the Sr3NiPtO6 electrode may be more susceptible to platinum migration.

  • 39.
    Klass, Verena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    A support vector machine-based state-of-health estimation method for lithium-ion batteries under electric vehicle operation2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 270, p. 262-272Article in journal (Refereed)
    Abstract [en]

    Capacity and resistance are state-of-health (SOH) indicators that are essential to monitor during the application of batteries on board electric vehicles. For state-of-health determination in laboratory environment, standard battery performance tests are established and well-functioning. Since standard performance tests are not available on-board a vehicle, we are developing a method where those standard tests are applied virtually to a support vector machine-based battery model. This data-driven model is solely based on variables available during ordinary electric vehicle (EV) operation such as battery current, voltage and temperature. This article contributes with a thorough experimental validation of this method, as well as the introduction of new features capacity estimation and temperature dependence. Typical EV battery usage data is generated and exposed to the suggested method in order to estimate capacity and resistance. These estimations are compared to direct measurements of the SOH indicators with standard tests. The obtained estimations of capacities and instantaneous resistances demonstrate good accuracy over a temperature and state-of-charge range typical for EV operating conditions and allow thus for online detection of battery degradation. The proposed method is also found to be suitable for on-board application in respect of processing power and memory restrictions.

  • 40.
    Klass, Verena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Capturing lithium-ion battery dynamics with support vector machine-based battery model2015In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 298, p. 92-101Article in journal (Refereed)
    Abstract [en]

    During long and high current pulses, diffusion resistance becomes important in lithium-ion batteries. In such diffusion-intense situations, a static support vector machine-based battery model relying on instantaneous current, state-of-charge (SOC), and temperature is not sufficient to capture the time-dependent voltage characteristics. In order to account for the diffusion-related voltage dynamics, we suggest therefore the inclusion of current history in the data-driven battery model by moving averages of the recent current. The voltage estimation performance of six different dynamic battery models with additional current history input is studied during relevant test scenarios. All current history models improve the time-dependent voltage drop estimation compared to the static model, manifesting the beneficial effect of the additional current history input during diffusion-intense situations. The best diffusion resistance estimation results are obtained for the two-step voltage estimation models that incorporate a reciprocal square root of time weighing function for the current of the previous 100 s or an exponential time function with a 20 s time constant (1–8% relative error). Those current history models even improve the overall voltage estimation performance during the studied test scenarios (under 0.25% root-mean-square percentage error).

  • 41.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Eriksson, Rickard
    Uppsala University.
    Groot, Jens
    Chalmers Technical University.
    Svens, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ciosek Högström, Katarzyna
    Uppsala University.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Berg, Helena
    Gustafson, Torbjörn
    Uppsala University.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Edström, Kristina
    Uppsala University.
    Non-uniform aging of cycled commercial LiFePO4//graphite cylindrical cells revealed by post-mortem analysis2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 257, p. 126-137Article in journal (Refereed)
    Abstract [en]

    Aging of power-optimized commercial 2.3 Ah cylindrical LiFePO4//graphite cells to be used in hybrid electric vehicle is investigated and compared for three different aging procedures; (i) using a simulated hybrid electric vehicle cycle within a narrow SOC-range, (ii) using a constant-current cycle over a 100% SOC-range, and (iii) stored during three years at 22 degrees C. Postmortem analysis of the cells is performed after full-cell electrochemical characterization and discharge. EIS and capacity measurements are made on different parts of the disassembled cells. Material characterization includes SEM, EDX, HAXPES/XPS and XRD. The most remarkable result is that both cycled cells displayed highly uneven aging primarily of the graphite electrodes, showing large differences between the central parts of the jellyroll compared to the outer parts. The aging variations are identified as differences in capacity and impedance of the graphite electrode, associated with different SEI characteristics. Loss of cyclable lithium is mirrored by a varying degree of lithiation in the positive electrode and electrode slippage. The spatial variation in negative electrode degradation and utilization observed is most likely connected to gradients in temperature and pressure, that can give rise to current density and potential distributions within the jellyroll during cycling.

  • 42. Le Van, K.
    et al.
    Groult, H.
    Mantoux, A.
    Perrigaud, L.
    Lantelme, F.
    Lindström, Rakel
    Badour-Hadjean, R.
    Zanna, S.
    Lincot, D.
    Amorphous vanadium oxide films synthesised by ALCVD for lithium rechargeable batteries2006In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, no 1, p. 592-601Article in journal (Refereed)
    Abstract [en]

    This study addresses the lithium insertion performances of amorphous vanadium oxide films, synthesized by atomic layer chemical vapour deposition (ALCVD). AFM and SEM investigations showed that the as-deposited films are amorphous, compact and homogeneous. As revealed by XPS and Raman spectroscopy, the ALCVD oxide films after deposition are mainly composed of V2O5, with V4+ surface content (about 10%). The insertion of Li+ into the lattice was investigated in 1 M LiClO4-PC. The results show that the electrochemical performances obtained with amorphous vanadium oxide films, with an optimal thickness of 200 nm (455 mAh g(-1), i.e. composition of Li2.9V2O5), were superior to crystalline V2O5 films. The amorphous films exhibit higher capacity and better cycle ability even for deep lithium insertion ratio compared to crystalline V2O5 films. The chemical diffusion coefficients, deduced from numerical simulation of chronopotentiograms, were comprised between 3 x 10(-12) and 10(-12) cm(2) s(-1) for a lithium insertion ratio comprised between 0 and 2.9. AFM and Raman spectroscopy performed before and after lithiation showed that neither the morphology nor the local order of the amorphous films were significantly affected by the insertion/extraction of lithium. Raman measurements also revealed that a very small amount of lithium are locally trapped in the oxide lattice.

  • 43. Lindström, B.
    et al.
    Pettersson, Lars J.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Development of a methanol fuelled reformer for fuel cell applications2003In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 118, no 02-jan, p. 71-78Article in journal (Refereed)
    Abstract [en]

    A compact methanol reformer for fuel cell vehicles (FCVs) has, been developed and successfully tested. The reformer which has been constructed to serve a 5 Me fuel cell operates by combined reforming of methanol (CRM) (a combination of steam reforming and partial oxidation). The exploitable energy surplus in a fuel cell vehicle is low and therefore a combustion system for heating the reformer which utilizes a catalyst for both evaporation and oxidation of liquid methanol was developed. We were able to obtain start-up times in the region of 4-6 min depending on the oxygen-to-methanol ratio (OMR) used for the combined reforming reaction. The main drawback from decreasing the start-up time by increasing the oxygen-to-methanol ratio was that the CO concentrations in the product stream increased. The reforming reaction was performed over copper-based catalysts while the oxidation took place over a mixture of platinum and manganese-based catalysts. The catalysts were characterized using SEM-EDS, BET surface area measurement and X-ray diffraction (XRD).

  • 44. Lindström, B.
    et al.
    Pettersson, Lars J.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Steam reforming of methanol over copper-based monoliths: the effects of zirconia doping2002In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 106, no 02-jan, p. 264-273Article in journal (Refereed)
    Abstract [en]

    In this paper, an experimental investigation concerning steam reforming of methanol over various alumina-supported monolithic copper-based catalysts is presented. The activity and carbon dioxide selectivity was studied over two sets of catalysts, one of which was doped with zirconium, with five different copper contents. The zirconium-doped catalyst were less active with respect to the hydrogen yield, however, they were at all times more selective towards carbon dioxide over the entire temperature interval. The catalysts have been characterised using Brunauer-Emmett-Teller (BET) surface area measurement and X-ray diffraction (XRD). The results show that the copper loading and modification of the active material by zirconia doping had a great influence on the methanol conversion and carbon dioxide selectivity of the steam reforming reaction.

  • 45.
    Liu, Peng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Aitola, K.
    Sveinbjörnsson, K.
    Zhang, J.
    Boschloo, G.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Design, synthesis and application of a π-conjugated, non-spiro molecular alternative as hole-transport material for highly efficient dye-sensitized solar cells and perovskite solar cells2017In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 344, p. 11-14Article in journal (Refereed)
    Abstract [en]

    Two low-cost, easily synthesized π-conjugated molecules have been applied as hole-transport materials (HTMs) for solid state dye-sensitized solar cells (ssDSSCs) and perovskite solar cells (PSCs). For X1-based devices, high power conversion efficiencies (PCEs) of 5.8% and 14.4% in ssDSSCs and PSCs has been demonstrated. For X14-based devices, PCEs were improved to 6.1% and 16.4% in ssDSCs and PSCs, respectively.

  • 46.
    Lundblad, Anders
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Schwartz, S.
    Bergman, B.
    Effect of sintering procedures in development of LiCoO2-cathodes for the molten carbonate fuel cell2000In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 90, no 2, p. 224-230Article in journal (Refereed)
    Abstract [en]

    LiCoO2-powder was synthesized from carbonate precursors by calcination in air. Greentapes were tape-cast using a non-aqueous slurry and 10 mu m plastic spheres as pore formers. Sintering was carried out in air at 850-950 degrees C and in argon/air at 500/750 degrees C, The two sintering procedures led to very different sub-micron morphologies, with the primary particles being much smaller in the latter case. The electrochemical performance at 650 degrees C, in terms of overpotential at 160 mA/cm(2), for the air- and argon/air-sintered electrodes was 57 and 81 mV, respectively. The potential drop due to contact resistance between electrode and current collector was estimated to be 100 and 70 mV, respectively. The electrode materials were characterized by scanning electron microscopy (SEM), Hg-porosimetry, the BET-method (N-2-adsorption), X-ray diffractometry (XRD), flame atomic absorption spectrometry (F-AAS), carbon analysis and a van der Pauw conductivity measurement set-up.

  • 47.
    Mikkola, Mikko
    et al.
    TKK.
    Tingelöf, Thomas
    VTT.
    Ihonen, Jari
    VTT.
    Modelling compression pressure distribution in fuel cell stacks2009In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 193, no 1, p. 269-275Article in journal (Refereed)
    Abstract [en]

    A general purpose 3D finite element method model has been developed for the estimation of the compression pressure distribution in fuel cell stacks. The model can be used for the optimisation of any type of fuel cell structure at any temperature. The model was validated with pressure sensitive film measurements using PEFC stack components that had low rigidity and were highly deformable.

  • 48.
    Miller, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Bazylak, A.
    A review of polymer electrolyte membrane fuel cell stack testing2011In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 196, no 2, p. 601-613Article, review/survey (Refereed)
    Abstract [en]

    This paper presents an overview of polymer electrolyte membrane fuel cell (PEMFC) stack testing. Stack testing is critical for evaluating and demonstrating the viability and durability required for commercial applications. Single cell performance cannot be employed alone to fully derive the expected performance of PEMFC stacks, due to the non-uniformity in potential, temperature, and reactant and product flow distributions observed in stacks. In this paper, we provide a comprehensive review of the state-of-the art in PEMFC testing. We discuss the main topics of investigation, including single cell vs. stack-level performance, cell voltage uniformity, influence of operating conditions, durability and degradation, dynamic operation, and stack demonstrations. We also present opportunities for future work, including the need to verify the impact of stack size and cell voltage uniformity on performance, determine operating conditions for achieving a balance between electrical efficiency and flooding/dry-out, meet lifetime requirements through endurance testing, and develop a stronger understanding of degradation.

  • 49.
    Mussa, Abdilbari Shifa
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 385, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The effects of external compression on the performance and ageing of NMC(1/3)/Graphite single-layer Li-ion pouch cells are investigated using a spring-loaded fixture. The influence of pressure (0.66, 0.99, 1.32, and 1.98 MPa) on impedance is characterized in fresh cells that are subsequently cycled at the given pressure levels. The aged cells are analyzed for capacity fade and impedance rise at the cell and electrode level. The effect of pressure distribution that may occur in large-format cells or in a battery pack is simulated using parallel connected cells. The results show that the kinetic and mass transport resistance increases with pressure in a fresh cell. An optimum pressure around 1.3 MPa is shown to be beneficial to reduce cyclable-lithium loss during cycling. The minor active mass losses observed in the electrodes are independent of the ageing pressure, whereas ageing pressure affects the charge transfer resistance of both NMC and graphite electrodes and the ohmic resistance of the cell. Pressure distribution induces current distribution but the enhanced current throughput at lower pressures cell does not accelerate its ageing. Conclusions from this work can explain some of the discrepancies in non-uniform ageing reported in the literature and indicate coupling between electrochemistry and mechanics.

  • 50.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Holmström, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Bodén, A.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Operating conditions affecting the contact resistance of bi-polar plates in proton exchange membrane fuel cells2013In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 231, p. 246-255Article in journal (Refereed)
    Abstract [en]

    Both ex-situ and in-situ measurements of contact resistance between gas diffusion layer (GDL) and bi-polar plate (BPP) were carried out using the same fuel cell hardware. Each BPP sample was submitted to ex-situ testing at room temperature, ex-situ testing in simulated fuel cell environment and in-situ testing, isolating the effect of specific operating conditions on the contact resistance. Increasing cell temperatures and relative humidity (RH) of the gases lowered the contact resistance. However, the presence of liquid water, measured as an increase in pressure drop over the cathode, affected the contact resistance negatively. High current density operation raises the temperature of the cell, but simultaneously increases the water content at the cathode, causing an increase of the contact resistance. In the case of uncoated steel 316L and gold-coated steel 316L, high current density operation for an extended period of time also caused a progressive deterioration of the contact resistance, which without this in-situ measurement could have been mistaken for other ohmic losses, e.g. increased membrane resistance due to metal ion poisoning.

12 1 - 50 of 79
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf