Nitrogen and boron coordinating atoms adjust single-atom catalyst anchored on divacancy defect graphene for highly efficient electrochemical oxygen reduction

Abstract

In this study, spin-polarized density functional theory (DFT) calculations were utilized to explore the oxygen reduction reaction (ORR) on a transition metal anchored to divacancy graphene (TM@dv-graphene). Our findings demonstrate that divacancy graphene serves as an effective substrate for stabilizing single transition metals, thereby facilitating the ORR. We elucidate the mechanisms of ORR by examining the adsorption of O₂, OOH, OH, 2OH, and O intermediates, and identifying two competing ORR pathways: the O* and 2OH* mechanisms. Most TM@dv-graphene catalysts predominantly favor the O* mechanism, with Rh and Ir being notable exceptions that preferentially follow the 2OH* mechanism. Moreover, catalysts co-coordinated with B and N atoms significantly enhance the adsorption of key intermediates, thereby improving ORR activity Specifically, the Co-N₄, Co-N₂B₂, Pd-N₂B₂, and Pt-N₂B₂ catalysts demonstrate promising ORR activity with lower overpotentials of 0.47, 0.46, 0.58, and 0.46 V, respectively. This work establishes a foundational framework for comprehending the electrochemical mechanisms of ORR, thus facilitating the design of highly efficient single-atom electrocatalysts.