Kinetic Effects of Temperature on Fe-N-C Catalysts for 2e- and 4e-Oxygen Reduction Reactions

Hydrogen peroxide (H2O2) formed via the two-electron oxygen reduction reaction (2e-ORR) on Fe-N-C catalysts at elevated temperatures can cause catalyst degradation in fuel cells. In this work, we studied the effects of temperature on the selectivity of Fe-N-C catalysts for the 2e- and 4e-ORRs in acidic electrolytes. The results showed that the H2O2 yield increased with increasing temperature, and prolonged high-temperature exposure under ORR polarization conditions led to catalyst degradation and higher H2O2 yield. These effects were further explained by means of a kinetic model describing the competitive reactions and the thermodynamics of the system.