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Influence of Operation Parameters on the Response of a PEMFC with Electrodeposited Pt‐WO 3 Cathode
Author(s) -
Martín A. J.,
Chaparro A. M.
Publication year - 2014
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201300242
Subject(s) - cathode , anode , proton exchange membrane fuel cell , materials science , hydrogen , chemical engineering , electrochemistry , analytical chemistry (journal) , microporous material , electrode , chemistry , catalysis , composite material , chromatography , organic chemistry , engineering
Pt‐WO 3 electrodes for proton exchange membrane fuel cells (PEMFC) have been prepared by electrodeposition on microporous carbon substrates. The electrodes have been studied as cathode in single cells under different operation conditions, including gas humidification, stoichiometry, and cell temperature. Polarization curves show a response qualitatively different from that observed with standard Pt/C cathodes, dominated by properties of the WO 3 phase. At low current densities, below ca. 400 mA cm –2 , the response is limited by protonic resistance and electrochemical kinetics in the cathode catalyst layer; at high current densities, large water retention by the hydrophilic cathode catalyst layer may cause anode flooding. Chemical changes in WO 3 phase accelerate at high temperature and under dry cathode conditions, compromising cell stability in the long term. Therefore, continuous and stable operation requires low humidification in the anode and high in the cathode. Also, a pronounced transient voltage response to current demand steps is observed at low cell voltage, which we attribute to the transition of the cathode potential to a mixed potential value, laying between the oxygen reduction and the hydrogen adsorption/desorption equilibrium mediated by spillover from Pt to the WO 3 phase. Basic kinetics considerations show how the height of the voltage transient is related with H spillover rate. Pt‐WO 3 cathode catalyst layer may have a practical interest as cathode for PEMFC when dry hydrogen inlet conditions are imposed, for instance, by the use of a metal hydride hydrogen storage system.