Vacancy Engineering in the First Coordination Shell of Single-Atom Catalysts for Enhanced Hydrogen and Oxygen Evolution Reactions.

Modulating the coordination environment of active centers has been proven to be an effective strategy for tuning the activity and selectivity of single-atom catalysts (SACs). However, most current research primarily focuses on altering non-metallic elements coordinating with the single metal atom. In this study, a novel approach is presented by introducing various vacancies into the first coordination shell of single-atom doped boron-carbon-nitride (BCN) catalysts, systematically evaluating their hydrogen evolution (HER) and oxygen evolution (OER) reactions performances. Results indicate that the introduction of vacancy defects enhances the stability of M-BCN structures. Furthermore, adjusting the coordinating atoms around metal sites modulates charge distribution, influencing the binding propensity of intermediates on the adsorption sites and promoting synergistic effects between metal and nonmetal, thereby altering catalytic activity. Specifically, among 147 M-BCN and M-BCN-vacancy structures, 17 catalysts with excellent HER performance have been identified. Notably, C-vacancy modulated Ni-BCN exhibits an OER overpotential of only 0.36V, suggesting that Ni-BCN-C1 may serve as an efficient multifunctional electrocatalyst for water-splitting reactions. This work employs vacancy engineering to precisely modulate the first coordination shell of single-atom catalysts, not only screening out efficient HER/OER electrocatalysts but also providing guidance for the development of potential BCN-based multifunctional electrocatalysts.