Evaluation of Electrolyte Additives for High-Temperature Polymer Electrolyte Fuel Cells

In this study, perfluoroalkyl phosphonic acids CF3PO3H2 and C2F5PO3H2 are investigated as additives to phosphoric acid to improve the oxygen reduction reaction (ORR) of high‐temperature polymer electrolyte (PEM) fuel cells. A comprehensive characterization of acid mixtures composed of 20 wt % additive and 80 wt % concentrated phosphoric acid is presented, ranging from ex situ measurements to in situ tests in operating high‐temperature PEM fuel cells. CF3PO3H2 and C2F5PO3H2 additives exhibit excellent thermal stability and are found to improve the wetting of the electrode. The fuel cell's output power increases consistently (240/270 mW cm−2 vs. 180 mW cm−2), owing to a decrease in the oxygen reduction reaction charge‐transfer resistance. Change of character: Perfluoroalkyl phosphonic acids are tested as electrolyte additives in high‐temperature polymer electrolyte (HT‐PEM) fuel cells. A comprehensive ex situ and in situ characterization is reported. These additives improve the fuel cell power output (240/270 mW cm−2 vs. 180 mW cm−2), owing to a decrease in oxygen reduction reaction charge‐transfer resistance.