First-Principles Study of Bonding-Driven Selectivity in CO ₂ Electroreduction on Metal–Nitrogen–Carbon Catalysts

Single-atom catalysts (SACs) have emerged as promising candidates for the carbon dioxide reduction reaction (CO2RR), and the design of new SACs is of great significance. This study introduces a series of transition metal SACs anchored on nitrogen-doped single-layer graphene (denoted as TM-C2N, with TM representing Fe, Ni, Cu, Pd, Ag, and Sn), designed for the selective conversion of CO2 to CO or formic acid. Utilizing first-principles computational approaches, the structural integrity, CO2 adsorption, and activation dynamics of these catalysts have been systematically investigated. Our findings reveal that the TM-C2N catalysts not only manifest exceptional structural stability but also exhibit superior CO2 adsorption and activation capabilities, coupled with an effective suppression of the competing hydrogen evolution reaction (HER). Gibbs free energy analyses have delineated distinct reaction pathways leading to HCOOH and CO formation on TM-C2N. Notably, Ni-C2N stands out as the most active catalysts, as evidenced by their favorable limiting potentials. The role of bonding interactions in elucidating the gas–solid interface adsorption mechanism is also highlighted. These insights offer valuable theoretical guidance for the fine-tuning of C2N-based catalysts in experimental settings and have broad implications for the development of efficient transition metal SACs for CO2 reduction.