Atomic-level engineering of single-atom catalysts for selective C-C coupling in CO2 hydrogenation to ethanol.

The selective hydrogenation of CO2 to ethanol represents a pivotal route for sustainable carbon utilization and renewable fuel production, yet its efficiency is fundamentally constrained by the C-C coupling step, which plays the pivotal, rate- and selectivity-determining role in this reaction. Single-atom catalysts (SACs) have emerged as transformative platforms for addressing this challenge, offering atomic-level control over active site geometry, electronic structure, and intermediate stabilization. This review comprehensively examines the design principles and mechanistic insights underlying SACs for selective CO2-to-ethanol conversion, with emphasis on atomic-scale engineering strategies that enhance C-C coupling while suppressing competing pathways. We discuss how tailored coordination environments, metal-support interactions, and defect engineering (e.g., oxygen vacancies) modulate the adsorption energetics of key intermediates (*CO, *CH x , and *CH x O) and transition states to favor ethanol formation. Advanced characterization and computational studies indicate that ternary interfacial structures, which consist of isolated metal sites, defect sites, and support cations, function as minimal functional units to optimize pathway selectivity. Furthermore, we highlight emerging strategies for enhancing SAC stability under practical conditions and address scalability challenges through advanced synthesis techniques like atomic layer deposition. Distinct from prior reviews, this review, by centering on atomic-level design principles and their direct impact on C-C coupling selectivity, provides a roadmap for developing high-performance SACs that achieve unprecedented ethanol selectivity and activity, paving the way toward industrial-scale CO2 valorization.