%0 Journal Article
%A Becker, Hans
%A Reimer, Uwe
%A Aili, David
%A Cleemann, Lars N.
%A Jensen, Jens Oluf
%A Lehnert, Werner
%A Li, Qingfeng
%T Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Eelctrolyte Membranes
%J Journal of the Electrochemical Society
%V 165
%N 10
%@ 0013-4651
%C Pennington, NJ
%I Electrochemical Soc.
%M FZJ-2018-03334
%P F863 - F869
%D 2018
%X The passage of an electrical current through phosphoric acid doped polymer membranes involves parasitic migration of the acid, which imposes a critical issue for long-term operation of the high temperature polymer electrolyte membranes fuel cell (HT-PEMFC). To elucidate the phenomenon, a three-layered membrane is constructed with embedded micro reference electrodes to measure phosphoric acid redistribution in a polybenzimidazole based membrane. Under a constant load, a concentration gradient develops due to the acid migration, which drives the back diffusion of the acid and eventually reaches a steady state between migration and diffusion. The acid gradient is measured as a difference in local ohmic resistances of the anode- and cathode-layer membranes by electrochemical impedance spectroscopy. The phosphoric acid diffusion coefficient through the acid doped membrane is about 10−11 m2 s−1, at least one order of magnitude lower than that of aqueous phosphoric acid solutions. The anion (H2PO4−) transference number is found to range up to 4% depending on current density, temperature and atmospheric humidity of the cell, implying that careful control of the operating parameters is needed in order to suppress the vehicular proton conduction as a degradation mitigation strategy.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000441061800113
%R 10.1149/2.1201810jes
%U https://juser.fz-juelich.de/record/848044