Cu-Mg Dual Single-Atom Catalysts with CO Spillover for Efficient CO₂ Electroreduction to CH₄

Selective electroreduction of CO₂ (CO₂RR) to CH₄ remains a significant challenge due to the complex multi-electron transfer process and competing C─C coupling pathways. Here, a Cu-Mg dual single-atom catalyst (CuN₂-MgN₂), which enables a spatially confined CO spillover mechanism was constructed. Spectroscopic characterization and density functional theory calculations confirmed that the atomically dispersed Mg sites not only modulate the electronic structure of Cu sites to lower the overall energy barrier of the CO₂RR to CH₄, but also efficiently activate CO₂ to form *CO intermediates, which subsequently migrate to adjacent Cu sites to further hydrogenate into CH₄. Leveraging these dual advantages, the optimized CuN₂-MgN₂ electrocatalyst achieved a CH₄ Faradaic efficiency of 78.3% and a partial current density of 228.7 mA cm^-2 at-1.1 V versus RHE under ambient CO₂ conditions, with the Turnover frequency of CH₄ on Cu single sites reaching up to 1.72 s^-1, dramatically outperforming currently reported catalysts. This work not only reveals the dynamic regulation mechanism of intermediates during CO₂-to-CH₄ conversion at the atomic scale but also establishes a universal theoretical model for designing industrial-grade electrocatalysts with well-defined active site configurations.