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 dyz and dz2 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.