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

Although single metal atoms (SMAs) have been extensively investigated as unique active sites in singleatom 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 (M-1) atoms and the neighboring host atoms of several M-1/g-C3N4 samples. The contributions of M-1 and host atoms towards the reduction of the OER/ORR overpotentials of Fe-1, Co-1, Ni-1, Cu-1 and Zn-1/g-C3N4, bifunctional electrocatalysts with the OER/ORR overpotentials of 0.50-0.70 V were investigated. Finally, new M-1/g-C3N4 catalysts with high OER/ORR performances could be estimated based on the d-band centre of the M-1 atoms in the future.