TY  - JOUR
AU  - Becker, Hans
AU  - Reimer, Uwe
AU  - Aili, David
AU  - Cleemann, Lars N.
AU  - Jensen, Jens Oluf
AU  - Lehnert, Werner
AU  - Li, Qingfeng
TI  - Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Eelctrolyte Membranes
JO  - Journal of the Electrochemical Society
VL  - 165
IS  - 10
SN  - 0013-4651
CY  - Pennington, NJ
PB  - Electrochemical Soc.
M1  - FZJ-2018-03334
SP  - F863 - F869
PY  - 2018
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000441061800113
DO  - DOI:10.1149/2.1201810jes
UR  - https://juser.fz-juelich.de/record/848044
ER  -