Highly Selective Toward HER or CO 2 RR by Regulating Cu Single and Dual Atoms on g‐C 3 N 4

Abstract Designing heterogeneous electrocatalysts with high activities and product selectivity toward desired electrocatalytic reactions remains a significant challenge in mitigating reliance on fossil fuels. Here, a controllable Cu‐based electrocatalysts system on graphitic carbon nitride (g‐C 3 N 4 ), where the atomic configuration of Cu species is precisely tuned to regulate catalytic behavior is reported. The Cu single‐atoms catalysts (Cu‐SACs) and aggregated Cu nanoparticles (Cu‐NP) embedded g‐C 3 N 4 contain only hydrogenated Cu atom sites, exhibit highly selective for hydrogen evolution reaction (HER), and are incapable for carbon dioxide reduction (CO 2 RR). In contrast, intercalated Cu dual‐atoms catalysts (Cu‐DACs) embedded g‐C 3 N 4 , incorporating both hydrogenated Cu atoms and intercalated Cu atoms sites, enable CO 2 RR while suppressing HER, demonstrating the critical role of intercalated Cu atoms in modulating selectivity. This structure–function relationship highlights the critical role of intercalated Cu‐DACs in modulating catalytic selectivity. A remarkable Faradaic efficiency of 88% methane during CO 2 RR is observed in Cu‐DACs systems, showcasing its potential in efficient product separation for industrial‐scale applications. This study not only demonstrates the functional importance of active site engineering in electrocatalysis but also highlights the high specificity, selectivity, and stability of Cu‐SACs and Cu‐DACs on g‐C 3 N 4 support, offering new insights into the design of efficient electrocatalysts for target reactions.