Copper-Based Bimetallic Catalysts for CO2 Hydrogenation to Methanol: Interfacial Synergy, Reaction Pathways, and Rational Design

CO2 hydrogenation to methanol is a key route for carbon recycling within the carbon capture, utilization, and storage (CCUS) framework. Cu-based catalysts are widely employed because of their low cost and high methanol selectivity, yet monometallic Cu suffers from sintering, limited CO2 activation, and competing reverse water-gas shift (RWGS) reactions. This review systematically summarizes recent advances in Cu-based bimetallic catalysts, categorized as Cu-p-block, Cu-noble metal, Cu-transition metal, and Cu-rare-earth metal systems. Throughout this review, the term “bimetallic catalysts” broadly refers to Cu-based systems containing a second metallic element, which may be present as a metallic alloy, an intermetallic compound, an atomically dispersed promoter species, or an oxide promoter or support component that forms Cu-M or Cu-MOx interfacial structures. Experimental findings and density functional theory calculations are integrated to clarify how second metals regulate electronic structures, interfacial sites, oxygen vacancies, and hydrogen activation, thereby governing the competition between the formate pathway and RWGS. The dynamic evolution of active sites and the concentration-dependent role of reaction-generated water are also discussed. Finally, current challenges in machine learning-assisted catalyst development are assessed, and future directions involving operando characterization, hydrophobic interface engineering, reactor-level water management, and interpretable data-driven catalyst design are proposed to guide catalyst optimization and practical implementation.