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

Manipulating the local microenvironments of single-atom catalysts is crucial for the product selectivity of CO electroreduction. Although theoretical research suggests that modifying the coordination structure of isolated Ni sites can promote the reduction of CO to CH, 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 CH. techniques and density functional theory calculations reveal that B coordination in the second shell of the Ni-N-C motifs (Ni-N-B/C) facilitates CO formation whereas incorporating B into the first shell (Ni-NB/C) significantly tunes the electronic structure of the Ni atoms, leading to electron delocalization, which enhances the *CO intermediate adsorption strength and makes CH the dominant product. This study marks the experimental realization of electrochemical CO-to-CH conversion at isolated Ni sites and underscores the importance of local coordination environment regulation in steering the reaction pathways of single-atom catalysts.