Boosting the oxygen reduction reaction activity of dual-atom catalysts on N-doped graphene by regulating the N coordination environment

Abstract

Development of low-cost and high-efficiency oxygen reduction reaction (ORR) catalysts is of significance for fuel cells and metal–air batteries. Here, by regulating the N environment, a series of dual-atom embedded N₅-coordinated graphene catalysts, namely M₁M₂N₅ (M₁, M₂ = Fe, Co, and Ni), were constructed and systematically investigated by DFT calculations. The results reveal that all M₁M₂N₅ configurations are structurally and thermodynamically stable. The strong adsorption of *OH hinders the proceeding of ORR on the surface of M₁M₂N₅, but M₁M₂N₅(OH₂) complexes are formed to improve their catalytic activity. In particular, FeNiN₅(OH₂) and CoNiN₅(OH₂) with the overpotentials of 0.33 and 0.41 V, respectively, possess superior ORR catalytic activity. This superiority should be attributed to the reduced occupation of d-orbitals of Fe and Co atoms in the Fermi level and the apparent shift of d_yz and d_z² orbitals of Ni atoms towards the Fermi level after adsorbing *OH, thus regulating the active sites and exhibiting appropriate adsorption strength for reaction intermediates. This work provides significant insight into the ORR mechanism and theoretical guidance for the discovery and design of low-cost and high-efficiency graphene-based dual-atom ORR catalysts.