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  • 51.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Appetecchi, Giovanni Battista
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Passerini, Stefano
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    The influence of air and its components on the cathodic stability of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 4, s. 1837-1842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although water- and air-stable ionic liquids have been in use for some years, experiments found in the literature are still per-formed in inert gas with ppm levels of oxygen and water. In this study, the influence of different environments (vacuum, argon, nitrogen, air and oxygen and water) on the cathodic electrochemical window of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) is reported and compared with investigations and processes found in the literature. The investigation indicates that this ionic liquid is highly stable in a vacuum and under argon flow. However, its cathodic stability is reduced in nitrogen and dry air. The simultaneous presence of water and air strongly affected the useful electrochemical window, as seen previously for imidazolium-based ionic liquids.

  • 52.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Capobianco, Paolo
    Ansaldo Fuel Cells S.p.A, Italien.
    Corrosion of anode current collectors in MCFC2005Inngår i: / [ed] Pierre Taxil, Catherine Bessada, Michel Cassir, Marcelle Gaune-Escard, 2005, s. 439-441Konferansepaper (Annet vitenskapelig)
  • 53.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Capobianco, Paolo
    Ansaldo Fuel Cells S.p.A.
    Corrosion of anode current collectors in molten carbonate fuel cells2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, nr 2, s. 782-788Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrosion of metallic parts is one of the life-time limiting factors in the molten carbonate fuel cell. In the reducing environment at the anode side of the cell, the corrosion agent is water. As anode current collector, a widely used material is nickel clad on stainless steel since nickel is stable in anode environment, but a cheaper material is desired to reduce the cost of the fuel cell stack. When using the material as current collector one important factor is a low resistance of the oxide layer formed between the electrode and the current collector in order not to decrease the cell efficiency. In this study, some candidates for anode current collectors have been tested in single cell molten carbonate fuel cells and the resistance of the oxide layer has been measured. Afterwards, the current collector was analysed in scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The results show that the resistances of the formed oxide layers give a small potential drop compared to that of the cathode current collector.

  • 54.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Scaccia, Silvera
    Hydrogen and Fuel Cells Project, ENEA.
    Investigation of a Ni(Mg,Fe)O Cathode for Molten Carbonate Fuel Cell Applications2007Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 7, nr 3, s. 218-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Molten Carbonate Fuel Cell (MCFC) converts chemical energy into electrical energy and heat. Since the working temperature is high, less expensive materials can be used compared to low temperature fuel cells. However, the components of the fuel cell still need to be improved. The dissolution of the NiO cathode has, for a long time, been a problem for the Molten Carbonate Fuel Cell (MCFC) and this area is still the focus for MCFC component research. In this study, solubility measurements for a NiC) cathode material doped with magnesium and iron are carried out and the electrochemical performance of this cathode material is tested under the standard conditions of the MCFC over 2,000 hours and compared with the performance of a standard NiO cathode. After operation, nickel precipitation in the matrices is investigated. It is concluded that a NiO cathode with magnesium and iron could be a viable candidate material for the MCFC.

  • 55.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Montanino, Maria
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Appetecchi, Giovanni B.
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Passerini, Stefano
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Effect of water and oxygen traces on the cathodic stability of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2008Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 22, s. 6397-6401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N-alkyl-N-methylpyrrolidinium (PYR1A') cations and bis(trifluoromethanesulfonyl)imide (TFSI-) anion, is reported. The extensive investigation performed by linear sweep voltarnmetry (LSV) and cyclic voltarnmetry (CV) indicates that the TFSl- anion is cathodically stable if the ionic liquid is pure and dry. The N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltarnmetry curves before the massive cation decomposition took place at very low potentials.

  • 56.
    Rashtchi, Hamed
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Acevedo Gomez, Yasna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Raeissi, Keyvan
    Shamanian, Morteza
    Eriksson, Björn
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Zhiani, Mohammad
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wreland Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of a PEM fuel cell using electroplated Ni–Mo and Ni–Mo–P stainless steel bipolar plates2017Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 13, s. F1427-F1436Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The performance and durability of 316L stainless steel bipolar plates (BPP) electroplated with Ni–Mo and Ni–Mo–P coatings are investigated in a proton exchange membrane fuel cell (PEMFC), using a commercial Pt/C Nafion membrane electrode assembly (MEA). The effect of the BPP coatings on the electrochemical performance up to 115 h is evaluated from polarization curves, cyclic voltammetry and electrochemical impedance spectroscopy together with interfacial contact resistance (ICR) measurements between the coatings and the gas diffusion layer. The results show that all the coatings decrease the ICR in comparison to that of uncoated 316L BPP. The Ni-Mo coated BPP shows a low and stable ICR and the smallest effects on MEA performance, including catalyst activity/usability, cathode double layer capacitance, and membrane and ionomer resistance build up with time. After electrochemical evaluation, the BPPs as well as the water effluents from the cell are examined by Scanning Electron Microscopy, Energy Dispersive and Inductively Coupled Plasma spectroscopies. No significant degradation of the coated surface or enhancement in metal release is observed. However, phosphorus addition to the coating does not show to improve its properties, as deterioration of the MEA and consequently fuel cell performance losses is observed.

  • 57.
    Rashtchi, Hamed
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Raeissi, K.
    Shamanian, M.
    Acevedo Gomez, Yasna
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rajaei, V.
    Evaluation of Ni-Mo and Ni-Mo-P Electroplated Coatings on Stainless Steel for PEM Fuel Cells Bipolar Plates2016Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 16, nr 6, s. 784-800Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stainless steel bipolar plates (BPPs) are the preferred choice for proton exchange membrane fuel cells (PEMFCs); however, a surface coating is needed to minimize contact resistance and corrosion. In this paper, Ni–Mo and Ni–Mo–P coatings were electroplated on stainless steel BPPs and investigated by XRD, SEM/EDX, AFM and contact angle measurements. The performance of the BPPs was studied by corrosion and conduction tests and by measuring their interfacial contact resistances (ICRs) ex situ in a PEMFC set-up at varying clamping pressure, applied current and temperature. The results revealed that the applied coatings significantly reduce the ICR and corrosion rate of stainless steel BPP. All the coatings presented stable performance and the coatings electroplated at 100 mA cm−2showed even lower ICR than graphite. The excellent properties of the coatings compared to native oxide film of the bare stainless steel are due to their higher contact angle, crystallinity and roughness, improving hydrophobicity and electrical conductivity. Hence, the electroplated coatings investigated in this study have promising properties for stainless steel BPPs and are potentially good alternatives for the graphite BPP in PEMFC.

  • 58.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    della Pietra, Massimiliano
    University of Perugia.
    McPhail, Stephen
    ENEA.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Molten carbonate fuel cells for CO2 separation and segregation by retrofitting existing plants - An analysis of feasible operating windows and first experimental findings2015Inngår i: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 35, s. 120-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as active carbon dioxide concentrator units are a promising solution to reduce greenhouse gas (GHG) emissions from traditional combustion plants. The cell reaction transfers carbonate ions from the cathode to the anode and allows the fuel cell to simultaneously produce power and separate CO2 from a stream of flue gas. Carbon dioxide separation is of high interest for use in natural gas combined cycles and coal gas combustion plants, as a large part of anthropogenic CO2 worldwide originates from such installations. The flue gas from these types of combustion technologies typically contains 3-15% CO2, which is in the lower operational range of the MCFC. The aim of this work was to investigate the possibility to retrofit existing power plants with MCFC to reduce the total release of CO2 without necessarily reducing the power output, and to understand which kind of power plant could have the major benefits with an MCFC retrofitting. The performance of lab scale MCFC fed with simulated flue gas was evaluated, and a number of operational parameters, such as utilization factor and cathode humidification were varied to study the effect on fuel cell performance. The results show that it is feasible to operate the MCFC as a CO2 separator for simulated gas turbine flue gas; however, the voltage drop due to low CO2 concentration may restrict the operating window depending on various operating conditions.

  • 59.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of MCFC fed with simulated flue gas2013Inngår i: EFC 2013 - Proceedings of the 5th European Fuel Cell Piero Lunghi Conference, 2013, s. 233-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The effect on MCFC performance with CO2 lean oxidant gas, simulating combustion flue gas was evaluated. Furthermore, measurements to test the effect of SO2 in the oxidant gas stream in concentrations up to 24ppm and during 90 min exposure, followed by regeneration with clean gas, was performed. Results show that the performance of the button cell with CO2 lean oxidant gas is acceptable at a base load of 100mA/cm2. The effect on fuel cell performance of short term exposure to SO2 is only clear in the higher range of contaminant concentration (>12ppm). Studying the performance degradation of the fuel cell caused by SO2 in flue gas is important for the use of MCFC as a CCS application.

  • 60.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Effect of sulfur contaminants on MCFC performance2014Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, nr 23, s. 12242-12250Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as carbon dioxide separation units in integrated fuel cell and conventional power generation can potentially reduce carbon emission from fossil fuel power production. The MCFC can utilize CO2 in combustion flue gas at the cathode as oxidant and concentrate it at the anode through the cell reaction and thereby simplifying capture and storage. However, combustion flue gas often contains sulfur dioxide which, if entering the cathode, causes performance degradation by corrosion and by poisoning of the fuel cell. The effect of contaminating an MCFC with low concentrations of both SO2 at the cathode and H2S at the anode was studied. The poisoning mechanism of SO2 is believed to be that of sulfur transfer through the electrolyte and formation of H2S at the anode. By using a small button cell setup in which the anode and cathode behavior can be studied separately, the anodic poisoning from SO2 in oxidant gas can be directly compared to that of H2S in fuel gas. Measurements were performed with SO2 added to oxidant gas in concentrations up to 24 ppm, both for short-term (90 min) and for long-term (100 h) contaminant exposure. The poisoning effect of H2S was studied for gas compositions with high- and low concentration of H-2 in fuel gas. The H2S was added to the fuel gas stream in concentrations of 1, 2 and 4 ppm. Results show that the effect of SO2 in oxidant gas was significant after 100 h exposure with 8 ppm, and for short-term exposure above 12 ppm. The effect of SO2 was also seen on the anode side, supporting the theory of a sulfur transfer mechanism and H2S poisoning. The effect on anode polarization of H2S in fuel gas was equivalent to that of SO2 in oxidant gas.

  • 61.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance degradation of Molten Carbonate Fuel Cells caused by SO2 in simulated flue gasManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The effect on MCFC performance degradation SO2 contaminant at the cathode, in combination with operating the fuel cell with CO2 lean oxidant gas, simulating combustion flue gas, was evaluated. Of special focus was the effect of electrolyte degradation.

     Measurements were performed to test the effect of SO2 in the oxidant gas stream, followed by regeneration with clean gas. A 3cm2 button cell MCFC allowing active electrolyte management by refilling was for 1500h to benchmark the performance degradation without contaminants. In order to study the poisoning effect of SO2 entering the fuel cell gas, the MCFC was operated for 250h with the addition of 18ppm SO2 in the oxidant gas. Electrolyte was added after 1500h of benchmark operation and after 250h of contaminant operation. The addition of 18ppm SO2 greatly accelerated the performance degradation of the fuel cell. Measurements showed that the internal resistance was the single factor which was most affected by the SO2 poisoning, and that the performance degradation after 250h was not reversed by regeneration with clean gas, but with the addition of fresh electrolyte. This led us to conclude that SO2 in oxidant gas leads to an accelerated loss of electrolyte and subsequent decrease in conductivity of the electrolyte, causing loss of performance and meeting end of life criteria after relatively short operational time. Other factors, such as poisoning of the anode and corrosion of cathode side current collectors, were also detected. 

  • 62. Ringuede, Armelle
    et al.
    Wijayasinghe, Athula
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Albin, Valerie
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cassir, Michel
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Solubility and electrochemical studies of LiFeO2-LiCoO2-NiO materials for the MCFC cathode application2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, nr 2, s. 789-795Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dissolution of the state-of-the-art lithiated NiO is still considered as one of the main obstacles to the commercialisation of the molten carbonate fuel cell (MCFC). Development of alternative cathode materials has been considered as a main strategy for solving this problem. Ternary compositions of LiFeO2, LiCoO2 and NiO are expected to decrease the cathode solubility while ensuring a good electrical conductivity and electrochemical activity towards the oxygen reduction. In this work, new material compositions in the LiFeO2-LiCoO2-NiO ternary system were synthesised using Pechini method and investigating their electrical conductivity by the DC four probe method. Then the influence of the cobalt content in the composition was determined in terms of AC impedance analysis and solubility measurements after 200 h of immersion in Li2CO3-Na2CO3 at 650 degrees C. The DC electrical conductivity study reveals the ability of improving the electrical conductivity, adequate for MCFC cathode application, by controlling the Co content of the composition. A special attention was given to the evolution of the open circuit potential as a function of time and to the impedance spectroscopy characterization related to microstructure modifications. Taking into account solubility, electrical conductivity, as well as electrochemical performance in the fuel cell, this study reveals the possibility of using LiFeO2-LiCoO2-NiO ternary materials for MCFC cathode.

  • 63. Ringuedé, A.
    et al.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE).
    Hildebrandt, Lars
    KTH, Skolan för kemivetenskap (CHE).
    Cassir, M.
    Overview on carbonate/oxide composite for high-temperature fuel-cells applications: Key points and breakthroughs2011Inngår i: EFC 2011 - Proceedings of the 4th European Fuel Cell Piero Lunghi Conference and Exhibition, 2011, s. 159-160Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Molten salt/oxide composites are in the heart of an intense field of research for high-temperature fuel cell devices. These electrolytes show a highly enhanced conductivity. This work isfocused on gadolinia-doped ceria and Li-K carbonate composites. It reviews the literature and presents recent results of the authors.

  • 64.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Guan, Tingting
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Ridell, Bengt
    Fuel cell based cogeneration: Comparison of electricity production cost for Swedish conditions2013Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, nr 10, s. 3858-3864Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A good portion of greenhouse gas emissions is caused by the energy used in the built environment. Emission reduction goals may be achieved by combining cogeneration with fuel cells (PC). This paper investigates electricity production costs for PC based cogeneration systems with recent data for Swedish conditions. The types of FCs that are investigated are proton exchange membrane PC and molten carbonate FC. Based solely on cost, PC based cogeneration systems cannot compete with conventional systems. However, our results show that Molten Carbonate PC based cogeneration systems will be profitable by 2020. To compete with conventional systems, the capital cost, lifetime and efficiency of FCs must be improved. Creation of a reasonably broad market is essential since it will greatly help to reduce capital costs and operation and maintenance (O&M) costs, the dominating parts of the overall costs according to the analysis.

  • 65.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    An Economical Comparison of Power-to-Gas Alternatives in Bozcaada - TurkeyManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Although currently conventional electricity generation methods dominate the market, the share of renewable energy systems is constantly increasing. Intermittent nature of solar and wind cause several problems. Power-to-gas is a method that can help with these problems by generating and storing hydrogen gas during off-peak hours so it can be reconverted into electricity via fuel cells and/or H2 internal combustion engines coupled with electricity generators during peak hours. In this study an economical evaluation of power-to-gas systems for an existing photovoltaic-Wind hybrid power system was made. Results indicate that although the photovoltaic-Wind may reduce the energy bill considerably when it is possible to sell electricity to the grid, coupling it with a power-to-gas system makes it unprofitable over the lifetime of the system.

  • 66.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Economic feasibility study of a fuel cell-based combined cooling, heating and power system for a data centre2016Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 111, s. 218-223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The energy use of data centres is increasing as the data storage needs increase. One of the largest items in the energy use of these facilities is cooling. A fuel cell-based combined cooling, heating and power system can efficiently meet such a centre's need for cooling and in the meantime generate enough electricity for the centre and more. In this paper the economic feasibility of a fuel cell-based combined cooling, heating and power system that meets the energy demands of such a facility is investigated using operational data from an existing data centre in Stockholm, Sweden. The results show that although the system is not feasible with current energy prices and technology it may be feasible in the future with the projected changes in energy prices.

  • 67. Wesselmark, M.
    et al.
    Wickman, B.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The impact of iridium on the stability of platinum on carbon thin-filmmodel electrodes2013Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 111, s. 152-159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasing the stability and lifetime of the electrodes is one of the most important factors in order to realise a large scale use of polymer electrolyte membrane fuel cells (PEMFC). By using well-defined thin-film model electrodes, the stability of Pt and Pt on Ir were examined as cathode catalysts in a single cell PEMFC setup. The electrodes were fabricated by evaporating thin layers of Pt and Pt on Ir onto the microporous layer of a gas diffusion layer. The amount of Pt deposited was equivalent to 3 nm (about 6.3 mu g cm(-2)) and the amount of Ir was varied between 1.5 nm and 20 nm (between 3.4 mu g cm(-2) and 45.3 mu g cm(-2)). All samples with Ir showed an increased stability over samples with sole Pt during cyclic corrosion test between 0.6V and 1.2V vs. the reversible hydrogen electrode. For thin layers of Ir, the initial activity for the oxygen reduction reaction was equal to or superior to that of sole Pt but for thicker Ir films it was somewhat lower. Hydrogen underpotential deposition and CO stripping were used to estimate the electrochemical surface area during the experiments and physical characterisation using scanning electron microscopy and X-ray photoelectron spectroscopy were used to determine the structure of the samples. The results suggest that Ir can stabilise Pt in the cathode electrode.

  • 68.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Degradation studies of PEMFC cathodes based on different types of carbon2009Inngår i: ECS Transactions, 2009, Vol. 25, nr 1 PART 2, s. 1241-1250Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study different accelerated degradation tests were used evaluating three different carbon supports as well as a thin model electrode. Cyclic ADTs, by 1000 cycles beween 0.6 and 1.2 V in nitrogen, did not degrade the porous electrodes to any larger extent in terms of oxygen reduction activity, whereas a significant loss of electrochemical surface area was seen, often more than 50%. Potentiostatic hold at 1.4 V during 3 h, did not permanently degrade the electrodes but instead an improved activity was obtained after rest during night. A correlation of increase in double layer capacitance and improved performance was seen and believed to be caused by the good proton conductivity of carbon surface oxides. CO-stripping peaks revealed that the humidity and wetting of Nafion™ may have caused the observed temporary changes during the potentiostatic hold. ©The Electrochemical Society.

  • 69.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methanol and formic acid oxidation in zinc electrowinning under process conditions2008Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 38, nr 1, s. 17-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibility of using methanol or formic acid oxidation as the anode process in zinc electrowinning was examined. The activity for methanol and formic acid oxidation on Pt coated high surface area electrodes was investigated over 36 h, at a current density used in industry. The activity could be maintained at a constant potential level in a synthetic electrowinning electrolyte if the current was reversed for short periods. During the tests, the anode potential was, more than 1.2 V below the potential for the oxygen evolving lead anodes used in modern zinc electrowinning. The lowered anode potential would lead to a significant energy reduction. However, tests in industrial electrolyte resulted in a very low activity for both methanol and formic acid oxidation. The low activity was shown to be caused mainly by chloride impurities. A reduction of the chloride content below 10(-5) M is needed in order to obtain sufficient activity for methanol oxidation on Pt for use in zinc electrowinning. Pt and PtRu electrodes were compared regarding their activity for methanol oxidation and the latter was shown to be more affected by chloride impurities. However, at a potential of 0.7 V vs NHE, with a chloride content of 10(-4) M, formic acid oxidation on PtRu gives the highest current density.

  • 70.
    Wesselmark, Maria
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Lagergren, Carina
    KTH, Tidigare Institutioner, Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Methanol oxidation as anode reaction in zinc electrowinning2004Inngår i: Electrode Processes VII / [ed] Birss, Evans, Josowicz and Osawa, 2004, s. 264-275Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The lead anodes used in zinc electrowinning today are not dimensionally stable and have a high overvoltage for oxygen evolution. By replacing the oxygen evolution in sulphate based electrolytes with methanol oxidation the anode potential could be lowered significantly. This would reduce the energy consumption and also enable the use of new and more stable types of electrodes. In this study, different types of electrodes were compared regarding their activity and stability for methanol oxidation in a zinc electrowinning environment. The activities of the electrodes studied were sufficient for electrowinning processes. The highest activity was obtained with porous PtRu, but platinised titanium was the most stable electrode. All electrodes were deactivated with time and the deactivation mechanism seemed to differ between Pt and PtRu. The best method for reactivation was to periodically reverse the current. The platinised titanium electrode was considered to be most suitable for use in electrowinning processes.

  • 71.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methanol oxidation as anode reaction in zinc electrowinning2005Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, nr 11, s. D201-D207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, different types of Pt- and PtRu-based electrodes were compared regarding their activity and stability for methanol oxidation in an acid zinc sulfate solution. The lead anodes used in zinc electrowinning today are not dimensionally stable and have a high overvoltage for oxygen evolution. By replacing the oxygen evolution in sulfate-based electrolytes with methanol oxidation, the anode potential could be significantly lowered. This would reduce the energy consumption and also enable the use of new and more stable types of electrodes. The activities of the electrodes studied were found sufficient for electrowinning. The highest activity was obtained with porous PtRu, while platinized titanium was the most stable electrode. All electrodes were deactivated with time, and the deactivation rate of PtRu was influenced by mass transport. The dominating reaction mechanism seemed to be different on Pt and on PtRu. Due to deactivation of the electrodes with time, a reactivation method was needed. The best method tested in this study was to periodically reverse the current. After assessing the electrodes with respect to important properties, the platinized titanium electrode was considered to be most suitable for use in electrowinning processes.

  • 72.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wickman, B.
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical performance and stability of thin film electrodes with metal oxides in polymer electrolyte fuel cells2010Inngår i: Electrochimica Acta, ISSN 0013-4686, Vol. 55, nr 26, s. 7590-7596Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin film electrodes are prepared by thermal evaporation of nanometer thick layers of metal oxide and platinum on a gas diffusion layer (GDL), in order to evaluate different metal oxides' impact on the activity and stability of the platinum cathode catalyst in the polymer electrolyte fuel cell. Platinum deposited on tin, tantalum, titanium, tungsten and zirconium oxide is investigated and the morphology and chemistry of the catalysts are examined with scanning electron microscopy and X-ray photoelectron spectroscopy. Cyclic sweeps in oxygen and nitrogen are performed prior and after potential cycling degradation tests. Platinum seems to disperse better on the metal oxides than on the GDL and increased electrochemically active surface area (ECSA) of platinum is observed on tin, titanium and tungsten oxide. A thicker layer metal oxide results in a higher ECSA. Platinum deposited on tungsten performs better than sole platinum in the polarisation curves and displays higher Tafel slopes at higher current densities than all other samples. The stability does also seem to be improved by the addition of tungsten oxide, electrodes with 3 nm platinum on 3, 10 and 20 nm tungsten oxide, performs better than all other electrodes after the accelerated degradation tests.

  • 73.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wickman, B.
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hydrogen oxidation reaction on thin platinum electrodes in the polymer electrolyte fuel cell2010Inngår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 12, nr 11, s. 1585-1588Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method for measuring the kinetics of the hydrogen oxidation reaction (HOR) in a fuel cell under enhanced mass transport conditions is presented. The measured limiting current density was roughly 1600 mA cmPt− 2, corresponding to a rate constant of the forward reaction in the Tafel step of 0.14 mol m− 2 s− 1 at 80 °C and 90% RH. The exchange current density for the HOR was determined using the slope at low overvoltages and was found to be 770 mA cmPt− 2. The high values for the limiting and exchange current densities suggest that the Pt loading in the anode catalyst can be reduced further without imposing measurable voltage loss.

  • 74.
    Wickman, Björn
    et al.
    Competence Centre for Catalysis, Department of Applied Physics, Chalmers.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Tungsten oxide in polymer electrolyte fuel cell: A thin-film model electrode study2011Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, nr 25, s. 9496-9503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films of WO(x) and Pt on WO(x) were evaporated onto the microporous layer of a gas diffusion layer (GDL) and served as model electrodes in the polymer electrolyte fuel cell (PEFC) as well as in liquid electrolyte measurements. In order to study the effects of introducing WO, in PEFC electrodes, precise amounts of WO(x) (films ranging from 0 to 40 nm) with or without a top layer of Pt (3 nm) were prepared. The structure of the thin-film model electrodes was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy prior to the electrochemical investigations. The electrodes were analyzed by cyclic voltammetry and the electrocatalytic activity for hydrogen oxidation reaction (HOR) and CO oxidation was examined. The impact of Nafion in the electrode structure was examined by comparing samples with and without Nafion solution sprayed onto the electrode. Fuel cell measurements showed an increased amount of hydrogen tungsten bronzes formed for increasing WO(x) thicknesses and that Pt affected the intercalation/deintercalation process, but not the total amount of bronzes. The oxidation of pre-adsorbed CO was shifted to lower potentials for WO(x) containing electrodes, suggesting that Pt-WO(x) is a more CO-tolerant catalyst than Pt. For the HOR. Pt on thicker films of WO(x) showed an increased limiting current, most likely originating from the increased electrochemically active surface area due to proton conductivity and hydrogen permeability in the WO(x) film. From measurements in liquid electrolyte it was seen that the system behaved very differently compared to the fuel cell measurements. This exemplifies the large differences between the liquid electrolyte and fuel cell systems. The thin-film model electrodes are shown to be a very useful tool to study the effects of introducing new materials in the PEFC catalysts. The fact that a variety of different measurements can be performed with the same electrode structure is a particular strength.

  • 75. Wijayasinghe, A.
    et al.
    Bergman, Bill
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Lagergren, Carina
    KTH, Tidigare Institutioner                               , Kemiteknik.
    LiFeO2-LiCoO2-NiO cathodes for molten carbonate fuel cells2003Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, nr 5, s. A558-A564Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dissolution of the state-of-the-art lithiated nickel oxide cathode is a major obstacle for the development of molten carbonate fuel cell (MCFC) technology. LiFeO2 and LiCoO2 were reported earlier as the most promising alternative materials; however, they do not satisfactorily substitute for the state-of-the-art cathode material. A solid solution consisting of LiFeO2, LiCoO2, and NiO is expected to posses some desirable properties of these three materials. Powder compositions in the LiFeO2-NiO binary system and a ternary subsystem with a constant 50:50 molar ratio of LiFeO2:NiO were prepared by the Pechini method. After preliminary powder characterizations, the feasibility of new materials for MCFC cathode application was studied. Electrical conductivity and microstructural characteristics were investigated, first in the form of bulk pellets and then in ex situ sintered porous gas diffusion cathodes. Finally, the electrochemical performance of selected cathodes was evaluated by short-time laboratory scale cell operations. The electrical conductivity of the ternary compositions with 50:50 molar ratio of LiFeO2:NiO increases significantly with increasing LiCoO2 content up to about 25 mol %. Further increase of LiCoO2 content decreases conductivity. The cell study indicates the possibility of preparing cathodes suitable for MCFC application with a considerably high LiFeO2 content.

  • 76. Wijayasinghe, A.
    et al.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    LiFeO2-LiCoO2-NiO materials for Molten Carbonate Fuel Cell cathodes. Part I: Powder synthesis and material characterization2006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 1-2, s. 165-173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ternary compositions of LiFeO2LiCoO2 and NiO are expected to posses desirable characteristics for the Molten Carbonate Fuel Cell (MCFC) cathode application. This paper presents a detailed description of the synthesis of LiFeO2-LiCoO2-NiO powders as well as dense sintered materials together with a brief discussion on the common aspects and trends observed in the characterization of these materials for MCFC cathode application. Feasibility of two wet-chemical powder preparation techniques, the Pechini method and the glycine-nitrate method, was investigated to obtain powders with characteristics appropriate for cathode fabrication. Materials in the LiFeO2-NiO binary system and five ternary subsystems, each with a constant molar ratio of LiFeO2/NiO while varying LiCoO2 content, were studied. Powders with characteristics appropriate for MCFC cathode fabrication could be obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on the calcination temperature and the material composition. The electrical conductivity study reveals the ability of preparing LiFeO2-LiCoO2-NiO materials with adequate electrical conductivity for MCFC cathode application.

  • 77. Wijayasinghe, A.
    et al.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    LiFeO2-LiCoO2-NiO materials for Molten Carbonate Fuel Cell cathodes. Part II. Fabrication and characterization of porous gas diffusion cathodes2006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 1-2, s. 175-184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    LiFeO2-LiCoO2-NiO ternary materials are considered as more viable alternatives to lithiated NiO2 in solving the cathode dissolution problem of the Molten Carbonate Fuel Cell (MCFC). This paper presents a detailed description of fabrication and characterization of LiFeO2-LiCoO2-NiO porous gas diffusion cathodes for MCFC, together with a brief discussion on the limitations and trends observed in cathode optimization. Several LiFeO2-LiCoO2-NiO ternary compositions and a LiFeO2-NiO binary composition, were fabricated into porous cathodes by tape casting and sintering. The sintered cathodes were subjected to phase analysis, electrical conductivity and pore structural characterization. A bimodal pore structure, appropriate for the MCFC cathode, could be achieved in sintered cathodes prepared using poreformers and sub-micron size powders. The amount of poreformers significantly influences the pore structure and the electrical conductivity of sintered cathodes. Furthermore, this study indicates the nature of the compromise to be made between the electrical conductivity, phase purity, pore structure and porosity in optimization cathodes for the MCFC application.

  • 78.
    Wijayasinghe, Athula
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Bergman, Bill
    KTH, Tidigare Institutioner, Materialvetenskap.
    Lagergren, Carina
    KTH, Tidigare Institutioner, Kemiteknik.
    A study on LiCoO2-rich cathode materials for the MCFC based on the LiCoO2-LiFeO2-NiO ternary system2004Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 49, nr 26, s. 4709-4717Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study performed in LiCoO2-rich LiCoO2-LiFeO2-NiO ternary materials for the molten carbonate fuel cell (MCFC) cathodes is reported in this paper. LiCoO2-LiFeO2-NiO ternary materials are considered as more viable alternatives to lithiated NiO, however, the work reported so far has mainly been focused on ternary compositions rich in LiFeO2 or NiO. The present work was carried out by investigating the electrical conductivity and microstructural characteristics of the new materials first in the form of bulk pellets and then in ex situ sintered porous-gas-diffusion (PGD) cathodes. The material study reveals the ability of preparing LiCoO2-LiFeO2-NiO ternary compositions with adequate electrical conductivity by controlling the LiCoO2 content. A bimodal pore structure, appropriate for the MCFC cathode, could be achieved in sintered cathodes prepared with fine powders and pore formers. Further, the cathode fabrication study indicates the nature of the compromise to be made between the electrical conductivity, phase purity, pore structure and porosity in optimization cathodes for MCFC application. The study shows the possibility of preparing LiCoO2-rich LiCoO2-LiFeO2-NiO cathodes with promising electrical and pore structural characteristics for the MCFC.

  • 79.
    Wijayasinghe, Athula
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    LiFeO2-LiCoO2-NiO cathodes for molten carbonate fuel cells2005Inngår i: / [ed] Pierre Taxil, Catherine Bessada, Michel Cassir, Marcelle Gaune-Escard, 2005, s. 425-429Konferansepaper (Annet vitenskapelig)
  • 80.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kortsdottir, Katrin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pérez Ferriz, Francisco Javier
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Conde Lopez, Julio Jose
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The Effect of Hydrocarbon Impurities in the Hydrogen Fuel on the Anode Activity in PEMFC2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The reformate fuel cell has recently gained increasing attention both for APUs in vehicles

    operating on diesel and in stationary applications such as micro-CHP operating on natural

    or biogas. In addition to hydrogen gas, reformate contain considerable amounts of CO2,

    nitrogen, water vapour and traces of CO, sulphur species and hydrocarbons. CO and H2S

    are well known poisons to the anode [1] but the influence of hydrocarbon species in the

    fuel cell has not been much investigated. We have previously investigated toluene [2] and

    ethene [3] on the anode Pt/C catalyst in the PEM fuel cell. In this paper we will discuss the

    influences of alkenes and alkanes in the light of some novel results on the effect of

    propene, propane and methane in the PEM fuel cell. We have especially focused on the

    adsorption and deactivation phenomena of low concentrations of contaminant on a Pt/C

    catalyst. In the experiments, in situ stripping voltammetry and on-line mass spectrometer

    were employed. The effects of adsorption potential and temperature are discussed. We

    show that propene is more poisonous to the Pt/C catalyst than ethene as it is adsorbed on

    the catalyst surface within the Hupd region and forms an adlayer that can be oxidized in two

    steps between 0.5-1 V (at 80°C, 90%RH) or be hydrogenated to propane in the Hupd region

    and in the presence of hydrogen.

  • 81.
    Wreland Lindström, Rakel
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Kortsdottir, Katrin
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Active Area Determination of Porous Pt Electrodes Used in Polymer Electrolyte Fuel Cells: Temperature and Humidity Effects2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 12, s. B1795-B1801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper discusses the proper measure of the electrochemically active area (ECA)of carbon supported Pt catalyst in PEM fuel cells employing in situ cyclic voltammetry. The charges of the hydrogen underpotential deposition (Hupd) and CO stripping peak obtained in situ are compared, and the influence of operation temperature (25–80°C) and relative humidity (40%–90%) is discussed. The results show that the charges of the Hupd decrease with rising temperature, while the corresponding charges of the CO stripping peak are essentially independent of temperature, at least at high relative humidity. The unexpectedly small Hupd charges are explained by the significant overlap with the hydrogen evolution reaction in a fuel cell at elevated temperatures. According to our results, it is proposed that a more reliable value of Pt ECA is estimated from the CO stripping charge. However, with decreasing humidity the charges of both Hupd and CO stripping peaks decrease, which is probably an effect of increasing blockage of Pt active sites by hydrophobic domains in the electrode ionomer. Some implications of varying cell conditions on the estimated Pt ECA and its correlation with fuel cell activity are discussed in an example from a fuel cell degradation test.

  • 82. Yli-Rantala, E.
    et al.
    Pasanen, A.
    Kauranen, P.
    Ruiz, V.
    Borghei, M.
    Kauppinen, E.
    Oyarce, Alejandro
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Darab, M.
    Sunde, S.
    Thomassen, M.
    Ma-Andersen, S.
    Skou, E.
    Graphitised Carbon Nanofibres as Catalyst Support for PEMFC2011Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 11, nr 6, s. 715-725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphitised carbon nanofibres (G-CNFs) show superior thermal stability and corrosion resistance in PEM fuel cell environment over traditional carbon black (CB) and carbon nanotube catalyst supports. However, G-CNFs have an inert surface with only very limited amount of surface defects for the anchorage of Pt catalyst nanoparticles. Modification of the fibre surface is therefore needed. In this study Pt nanoparticles have been deposited onto as-received and surface-modified G-CNFs. The surface modifications of the fibres comprise acid treatment and nitrogen doping by pyrolysis of a polyaniline (PANI) precursor. The modified surfaces were studied by FTIR and XPS and the electrochemical characterization, including long-term Pt stability tests, was performed using a low-temperature PEMFC single cell. The performance and stability of the G-CNF supported catalysts were compared with a CB supported catalyst and the effects of the different surface treatments were discussed. On the basis of these results, new membrane electrode assemblies (MEAs) were manufactured and tested also for carbon corrosion by in situ FTIR analysis of the cathode exhaust gases. It was observed that the G-CNFs showed 5?times lower carbon corrosion compared to CB based catalyst when potential reached 1.5?V versus RHE in simulated start/stop cycling.

12 51 - 82 of 82
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