Dual-Atom Metal and Nonmetal Site Catalyst on a Single Nickel Atom Supported on a Hybridized BCN Nanosheet for Electrochemical CO₂ Reduction to Methane: Combining High Activity and Selectivity

Atomically dispersed nitrogen-coordinated transition-metal sites supported on graphene (TM–N₄–C) offer promising potential for the electrochemical carbon dioxide reduction reaction (CO₂RR). However, a few TM–N_x–C single-atom catalysts (SAC) are capable of reducing CO₂ to multielectron products with high activity and selectivity. Herein, using density functional theory calculations, we investigated the electrocatalytic performance of a single TM atom embedded into a defective BCN nanosheet for CO₂RR. The N and B atom co-coordinated TM center, namely, TM–B₂N₂, constructs a symmetry-breaking site, which strengthens the overlapping of atomic orbitals, and enables the linear CO₂ to be curved and activated, compared to the weak coupling of CO₂ with the symmetric TM–N₄ site. Moreover, the TM–B₂N₂ sites play a role of dual-atom active sites, in which the TM atom serves as the carbon adsorption site and the B atom acts as the oxygen adsorption site, largely stabilizing the key intermediates, especially *COOH. The symmetry-breaking coordination structures shift the d-band center of the TM atom toward the Fermi level and thus facilitate CO₂ reduction to hydrocarbons and oxygenates. As a result, different from the TM–N₄–C structure that leads to CO as the major product, the Ni atom supported on BCN can selectively catalyze CO₂ conversion into CH₄, with an ultralow limiting potential of −0.07 V, while suppressing the hydrogen evolution reaction. Our finding suggests that introduction of a nonmetal active site adjacent to the metal site provides a new avenue for achieving efficient multi-intermediate electrocatalytic reactions.