Generalized Encapsulations of ZIF-Based Fe–N–C Catalysts with Controllable Nitrogen-Doped Carbon for Significantly-Improved Stability Toward Oxygen Reduction Reaction

Abstract

The vigorous development of efficient platinum group metal-free catalysts is considerably important to facilitate the universal application of proton exchange membrane fuel cells. Although nitrogen-coordinated atomic iron intercalated in carbon matrix (Fe–N–C) catalysts exhibit promising catalytic activity, the performance in fuel cells, especially the short lifetime, remains an obstacle. Herein, a highly-active Fe–N–C catalyst with a power density of >1 w cm^-2 and prolonged discharge stability with a current density of 357 mA cm^-2 after 40 h of constant voltage discharge at 0.7 V in H₂–O₂ fuel cells using a controllable and efficient N–C coating strategy is developed. It is clarified that a thicker N–C coating may be more favorable to enhance the stability of Fe–N–C catalysts at the expense of their catalytic activity. The stability enhancement mechanism of the N–C coating strategy is proven to be the synergistic effect of reduced carbon corrosion and iron loss. It is believed that these findings can contribute to the development of Fe–N–C catalysts with high activity and long lifetimes.