Modulating the local microenvironment over isolated nickel sites through first-shell coordination to regulate the reaction pathway of CO2 electroreduction

Manipulating the local microenvironments of single-atom catalysts is crucial for the product selectivity of CO₂ electroreduction. Although theoretical research suggests that modifying the coordination structure of isolated Ni sites can promote the reduction of CO₂ to CH₄, there is still no experimental evidence to date. Herein, by regulating the coordination shell of boron (B) surrounding the Ni central atom, we have achieved the transformation of the reduction product from CO to CH₄. <i>In situ</i> techniques and density functional theory calculations reveal that B coordination in the second shell of the Ni-N-C motifs (Ni-N₄-B/C) facilitates CO formation whereas incorporating B into the first shell (Ni-N₃B₁/C) significantly tunes the electronic structure of the Ni atoms, leading to electron delocalization, which enhances the *CO intermediate adsorption strength and makes CH₄ the dominant product. This study marks the experimental realization of electrochemical CO₂-to-CH₄ conversion at isolated Ni sites and underscores the importance of local coordination environment regulation in steering the reaction pathways of single-atom catalysts.