Recent advances in nanoalloys for selective electrochemical CO2 reduction.

The electrochemical carbon dioxide reduction reaction (CO2RR) represents a compelling strategy to close the anthropogenic carbon cycle by converting CO2 into fuels and chemicals using renewable electricity. Despite significant advances, the performance of CO2RR catalysts remains fundamentally constrained by linear scaling relationships in monometallic systems, which couple the adsorption energetics of key intermediates. This intrinsic limitation restricts independent optimization of reaction steps, leading to poor selectivity, high overpotentials, and persistent competition from the hydrogen evolution reaction (HER). Nanoalloy catalysts have emerged as a powerful platform to overcome these constraints by introducing atomic-scale heterogeneity that is inaccessible to single-metal surfaces. Through controlled integration of multiple elements, nanoalloys enable decoupling of adsorption energetics, generation of distinct active sites, and spatial separation of reaction functions, thereby allowing selective stabilization of intermediates and access to reaction pathways that are thermodynamically or kinetically disfavored on monometallic catalysts. In this review, we move beyond conventional composition-based classifications and present a product-centered framework that directly connects nanoalloy design principles with CO2RR reaction pathways and target products. We highlight three central synergistic mechanisms that govern nanoalloy behavior: electronic effects arising from d-band center modulation, strain effects induced by lattice mismatch, and ensemble effects enabled by tandem catalysis. We discuss how rational control of these mechanisms, together with microenvironment engineering, provides leverage over local reaction kinetics and selectivity, spanning syngas production, C1 oxygenate formation, and C-C coupling toward C2+ products. Finally, we outline remaining challenges and emerging opportunities in nanoalloy catalyst design, emphasizing strategies to bridge atomic-level mechanistic insight with durable, scalable systems for industrial CO2 electrolysis.