Single atom catalysts supported on metallic C5N monolayers for oxygen reduction/evolution reactions with more active sites than loaded metal atoms

Abstract

Single atom catalysts (SACs) supported by carbonaceous materials present extraordinary activity for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which however suffer from low loadings of transition metal (TM) atom. We here proposed a strategy of designing SACs toward ORR/OER containing higher number of active sites than that of loaded TM atoms, which include not only the metal centers but also the non-metal atoms activated by the doping of TM atoms. By incorporating TM atoms of Fe, Co and Ni into our previously predicted metallic monolayers of C5N, we investigated their ORR/OER activities and found that orthorhombic-C5N supported Co atoms coordinated with three C atoms and one N atom can serve as superior bifunctional electrocatalysts for both ORR and OER with overpotentials of 0.38 and 0.3 V, respectively. Our density functional theory calculations also demonstrate that the structural configurations of the first, second and even outer coordination sphere of metal centers can simultaneously affect the catalytic performance of SACs. This study provides a novel idea to address the challenge faced by the SACs toward ORR/OER caused by the low loadings of TM atoms and obscure structure-property relationship.