High-performance screening of carbon-nitride single-atom catalysts for oxygen electrode reaction in rechargeable metal–air batteries

The sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are the oxygen electrode reactions, impede further advancements in metal–air batteries technology. The main objective is to investigate the bifunctional catalytic activity of the VIIB, VIII, IB, and IIB groups transition metals doped carbon-nitride material (C9N4, C10N9, C13N3, C14N12, and C19N3) as bifunctional electrocatalysts for oxygen electrode reaction in metal–air batteries by density functional theory methods in this paper. C9N4, C13N3, and C19N3 are better doping substrates than C10N9 and C14N12 for all transition metals. For ORR, Co-C9N4, Cu-C13N3, Rh-C13N3, Co-C19N3, Ni-C19N3, and Cu-C19N3 exhibit the overpotential values of 0.36, 0.37, 0.40, 0.47, 0.48, and 0.48 V, respectively. These values are comparable to or even better those of Pt(1 1 1), indicating their exceptional ORR catalytic activity. For OER, Rh-C9N4, Pt-C9N4, Co-C13N3, Rh-C13N3, and Ni-C19N3 possess the overpotential values of 0.42, 0.40, 0.40, 0.33, and 0.41 V, respectively, showcasing a remarkable similarity to that of RuO2(1 1 0). Rh-C13N3 exhibits superior bifunctional catalytic activity (Bifunctional Index = 0.73 V). This study offers essential theoretical guidance for the utilization of carbon-nitride single-atom catalysts as bifunctional electrocatalysts in the oxygen electrode reaction of rechargeable metal-air batteries.