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.