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.