Out-of-plane FeII–N4 moiety modified Fe–N co-doped porous carbons as high-performance electrocatalysts for the oxygen reduction reaction

Abstract

Exploring high-performance iron and nitrogen co-doped carbon (Fe–N–C) electrocatalysts with desirable active sites toward the oxygen reduction reaction (ORR) is extremely important for future applications of fuel cells and metal–air batteries. Herein, we demonstrate a facile and effective strategy for the synthesis of high-performance Fe–N–C electrocatalysts by pyrolyzing a physical mixture of conventional carbon black (Black Pearls 2000, BP2000) and Hemin followed by a post-treatment procedure including acid-washing and heat-treatment. The resultant Fe–N–C electrocatalysts possessed numerous out-of-plane Fe^II–N₄ moieties (D1 sites) uniformly distributed in the porous carbon matrix, and a well-defined micro/mesoporous structure that is expected to significantly improve the ORR activity in both alkaline and acidic electrolytes. In an alkaline electrolyte, the Fe–N–C electrocatalyst exhibited a remarkable ORR activity with a high onset potential of 0.942 V and a half-wave potential of 0.848 V, which were 9 mV and 12 mV more positive than those of the commercial Pt/C, respectively, while its half-wave potential was 0.73 V, only 60 mV less than that of Pt/C in an acidic electrolyte. Furthermore, the Fe–N–C electrocatalyst also demonstrated better electrochemical durability and methanol tolerance in comparison with Pt/C in both alkaline and acidic electrolytes. This work opens a new avenue for the rational design and synthesis of highly active and durable TM–N–C electrocatalysts towards ORR.