ZIF-L-derived FeN–hcC catalysts with curved carbon surfaces for effective oxygen reduction reaction over the entire pH range†

Abstract

The development of highly active and stable iron–nitrogen (Fe–N_x) based oxygen reduction reaction (ORR) catalysts with pH versatility is one of the future directions of electrochemical energy. However, the task of designing and controlling the three-dimensional local structure of Fe species to obtain high ORR activity and stability remains a challenge. In this study, we prepared hierarchical porous FeN–_hcC (iron–nitrogen–_{highly curved} carbon) catalysts derived from ZIF-L by a soft template method. The highly curved carbon surface possibly results in a compressive strain effect on the supported Fe–N_x active site, which can not only enhance the high exposure of the active site to improve the electrocatalytic activity, but also facilitate the stability of the Fe–N_x site during the ORR catalytic process. FeN–_hcC-1 exhibited a high half-wave potential of 0.89, 0.77 and 0.82 V vs. RHE in alkaline, acidic, and neutral media, respectively. In addition, after cyclic durability tests in different electrolyte environments, good stability is still maintained, which is significantly better than the planar Fe–N_x site and Pt/C catalyst. This work provides a new synthetic strategy for the construction of highly curved surfaces of carbon materials, while inspiring a method to improve the ORR performance of ZIF-derived materials.