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

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 N 5 -coordinated graphene catalysts, namely M 1 M 2 N 5 (M 1 , M 2 = Fe, Co, and Ni), were constructed and systematically investigated by DFT calculations. The results reveal that all M 1 M 2 N 5 configurations are structurally and thermodynamically stable. The strong adsorption of *OH hinders the proceeding of ORR on the surface of M 1 M 2 N 5 , but M 1 M 2 N 5 (OH 2 ) complexes are formed to improve their catalytic activity. In particular, FeNiN 5 (OH 2 ) and CoNiN 5 (OH 2 ) 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 z 2 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.