Unexpected monoatomic catalytic-host synergetic OER/ORR by graphitic carbon nitride: density functional theory

Abstract

Although single metal atoms (SMAs) have been extensively investigated as unique active sites in single-atom catalysts, the possible active sites of the host catalysts have been unfortunately neglected in previous studies. In single-atom catalysts, the SMAs can promote the chemical and catalytic activities of host atoms, which may act as secondary active sites, resulting in a significant synergistic effect on the catalytic performance. Using density functional theory calculations, we studied the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) on two different types of active sites: single metal (M₁) atoms and the neighboring host atoms of several M₁/g-C₃N₄ samples. The contributions of M₁ and host atoms towards the reduction of the OER/ORR overpotentials of Fe₁, Co₁, Ni₁, Cu₁ and Zn₁/g-C₃N₄, bifunctional electrocatalysts with the OER/ORR overpotentials of 0.50–0.70 V were investigated. Finally, new M₁/g-C₃N₄ catalysts with high OER/ORR performances could be estimated based on the d-band centre of the M₁ atoms in the future.