Carboxylate trapping engineering to fabricate monodispersed dual-atom iron sites for efficient oxygen reduction

Abstract

Atomically dispersed iron–nitrogen coordinated active sites on carbon (Fe–N–C) are considered to be absorbing materials that can be used as alternatives to Pt-based catalysts for the electrochemical oxygen reduction reaction (ORR). However, Fe–N–C catalysts exhibit low metal loadings and unsatisfactory performance due to the imperfect electronic structure. Herein, atomically dispersed binary Fe–Fe dual-atom sites supported on hierarchically ordered porous N-doped carbon (denoted as FeNC-OAc) were synthesized via a universal carboxylate-assisted strategy. The iron ions could be stabilized by carboxylate, which promoted the formation of a Fe–Fe dual-atom catalyst with dense accessible active sites. Thanks to the high activity and accessibility of binary Fe–Fe active sites, the optimized 0.2FeNC-OAc catalyst exhibited superior oxygen reduction performance in alkaline solution, with a half-wave potential (E_1/2) of 0.875 V, much higher than commercial 40 wt% Pt/C (0.853 V). Moreover, it displayed superior tolerance to methanol cross effects and electrochemical durability. This work affords a general method for the rapid preparation of electrocatalysts with bimetal active sites, which may promote the application of various atomic catalysts.