Single-atom site modulation of Cu electrocatalysts for CO2 electroreduction.

Copper is the only metal capable of efficiently converting CO2 into multi-carbon (C2+) products, yet its practical application is hindered by poor intrinsic selectivity, complex active sites, and limited pathway control. Single-atom site modified Cu catalysts (SAMCs) offer an effective strategy to overcome these challenges by introducing atomically dispersed heterometallic sites that retain the C-C coupling ability of Cu while precisely regulating CO2 activation, C-C coupling, and hydrogen-transfer kinetics through interfacial synergy. This review summarizes recent advances in SAMCs for CO2 electroreduction. We first introduce synthetic strategies for constructing isolated sites on Cu, including electrochemical reconstruction, electrodeposition, galvanic replacement, vacancy-mediated cation exchange, and co-reduction. We then discuss the mechanisms of single-atom regulation in CO2 activation, C-C coupling, and hydrogen transfer. Finally, we highlight emerging design principles, including the 10-electron counting rule, d-p orbital matching, and data-driven catalyst discovery, while outlining challenges in active-site identification, stability under industrial conditions, and electrolyzer integration. This review provides mechanistic insights and design guidelines for developing efficient Cu-based single-atom catalysts and practical CO2 electrolysis systems.