Selective anode catalyst for the mitigation of start-up/shut-down induced cathode degradation in proton exchange membrane fuel cells

Abstract

Reducing cathode degradation during start-up and shut-down (SUSD) events is one of the remaining challenges for the widespread application of proton exchange membrane fuel cells (PEMFC). An anode catalyst that is selective for the hydrogen oxidation reaction (HOR) while its activity for the oxygen reduction reaction (ORR) is severely reduced, could substantially prolong the SUSD lifetime of the cathode. Herein, we report on single-cell measurements with a Pt/TiOx/C (x ≤ 2) catalyst that has been shown to be HOR selective by rotating disk electrode (RDE) measurements. The HOR activity of the catalyst was compared to conventional Pt/C by H2-pump measurements at ultra-low loadings. The ORR activity of Pt/TiOx/C was compared to Pt/C anodes with high and low Pt loadings, showing a diminished selectivity in MEA compared to RDE measurements. Unfortunately, the PEMFC performance with the Pt/TiOx/C catalyst was compromised by TiOx dissolution, deduced from voltage loss analysis of the H2/O2 performance curves and by ex-situ SEM/EDX of the MEAs. Finally, the successful mitigation of cathode carbon corrosion was shown over the course of 3200 SUSD cycles, whereby the retention of Pt surface area when using a Pt/TiOx/C anode by far exceeded the improvements expected from the reduced ORR kinetics.