First-principle calculations study of oxygen reduction electrocatalyst: Single transition metal supported on a brand-new graphitic carbon nitride (g-C7N3) substrate

Single-atom catalysts (SACs) possess promising potential as materials to catalyze oxygen reduction reaction (ORR) on account of high atomic utilization efficiency, tunable electronic structure, and exceptional catalytic performance. The ORR activities of graphite carbonitride (g-C7N3) supported 3d, 4d, and 5d transition metals are investigated. Eleven kinds of TM-C7N3 structures have been found to have good stability by computing formation energy and dissolution potential. Furthermore, density of states analysis shows a strong interaction of the metal atom and the coordination N atoms, which gives satisfactory stability of TM-C7N3. Among eleven TM-C7N3, the binding energy of reaction species on Rh-C7N3, Ni-C7N3, and Pt-C7N3 are closer to those of Pt(111), showing that they have good ORR activity. In addition, good linear relationships exist between the adsorption free energy of *OH (∆G*OH) and that of *OOH and *O, implying that ∆G*OH can be put forward as a trustworthy activity descriptor. Promisingly, the ηORR values of Rh-C7N3, Ni-C7N3, and Pt-C7N3 are 0.32, 0.38, and 0.44 V, respectively, even lower than the overpotential value of Pt(111). This suggests that these three catalysts demonstrate superior catalytic activity compared to Pt(111).