Engineering bimetallic and multi-metallic single-atom catalysts for photo/electrocatalytic CO2 conversion into high-value products

Photo/Electrocatalytic CO 2 reduction (CO 2 R) into value-added fuels and chemicals offers a sustainable route to mitigate carbon emissions and store renewable energy. However, its practical deployment is constrained by sluggish kinetics, competing hydrogen evolution, and limited selectivity toward multi-carbon products, underscoring the need for high-performance catalysts. Bimetallic and multi-metallic single-atom catalysts have emerged as a transformative platform to address these challenges, combining atomic-level precision, tunable electronic structures, and synergistic interactions between adjacent metal centers. This review critically examines the fundamental principles, synthetic strategies, advanced characterization techniques, and catalytic performance of bimetallic and multi-metallic SACs for CO 2 conversion into value-added single-carbon and multi-carbon products. It highlights how electronic structure modulation, charge redistribution, and tandem site engineering enable the stabilization of key intermediates, mitigate scaling relationships, suppress competing reactions, and promote C–C coupling. State-of-the-art operando spectroscopy and density functional theory calculations provide mechanistic insights into structure–activity–selectivity relationships at the atomic level. Despite remarkable advances in Faradaic efficiency, current density and durability, challenges remain in scalable synthesis, long-term stability, and device-level integration which are critically assessed. The emerging directions including adaptive active sites, AI-assisted catalyst discovery, and integrated reactor engineering are elaborated which will improve bimetallic and multi-metallic SACs for converting CO 2 into value-added materials.