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The Electrochemical Behavior of Phosphoric‐Acid‐Doped Poly(perfluorosulfonic Acid) Membranes
Author(s) -
Aili David,
Savinell Robert F.,
Jensen Jens Oluf,
Cleemann Lars N.,
Bjerrum Niels J.,
Li Qingfeng
Publication year - 2014
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201402053
Subject(s) - phosphoric acid , membrane , anode , anhydrous , sulfonic acid , conductivity , diffusion , electrochemistry , doping , proton , materials science , electrical conductor , limiting current , chemistry , thermal conduction , cathode , inorganic chemistry , chemical engineering , polymer chemistry , organic chemistry , composite material , electrode , optoelectronics , biochemistry , physics , quantum mechanics , engineering , thermodynamics
Abstract Highly conductive phosphoric‐acid‐doped poly(perfluorosulfonic acid) membranes have long been known to malfunction in fuel cells. This is investigated and found to be due to failure of the anode, in which a limiting current is observed in the very low current‐density range. It is proposed that the strongly acidic sulfonic acid groups protonate the phosphoric acid under anhydrous conditions, forming excess proton defects that are involved in proton conduction by means of the vehicle mechanism. The slow back‐diffusion of phosphoric acid molecules as proton carriers thus limits the long‐range conductivity of the membranes during fuel cell operation. The hypothesis is experimentally verified using a specially designed half‐cell test.