(2fc) Theory-Guided Modulation of Local Coordination Environment of Single-Atom Metal Site Catalysts for Enhanced Oxygen Reduction Reaction

The development of high-performance oxygen reduction reaction catalysts is essential in sustainable energy technologies, such as fuel cells and metal-air batteries. Single-metal-atom site catalysts (SAC) such as metal-N-doped carbon (M-N-C) have been highlighted as a possible cost-effective oxygen reduction reaction catalyst (ORR). To go beyond the state-of-the-art Pt/C, a new design strategy to modulate the electronic structure of the material is necessary. For example, breaking the symmetry of nitrogen ligand to substitute another heteroatom has influenced the binding strength of the ORR intermediates, hence enhancing the ORR activity. Also, to theoretically investigate the ORR activity of a single-atom catalyst in an electrochemical environment, the active site under operating conditions should be considered; however, few studies have yet taken this into account. In this study, we employed screening of SACs where a transition metal atom is coordinated by one or two types of heteroatoms (B, C, N, O, S, and P) embedded in a graphene structure. We investigated how the change in the active site environment promotes ORR activity. In addition, we examined the configuration of the active site of SACs and the ORR mechanism under operating conditions through microkinetic analysis and modeling of the interface between electrolyte and surface. Our findings will provide useful guidance for designing novel ORR catalysts.