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

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 (E1/2) 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. Atomically dispersed catalysts with dense accessible Fe-Fe binary active sites supported on hierarchically ordered porous N-doped carbon are prepared via a general carboxylate-assisted strategy and they display drastically enhanced ORR activity.