Designing Copper-Based Catalysts for High Selectivity in Electrocatalytic CO2 Reduction: From Single/Dual Atoms to Nanoclusters and Nanoparticles.

Electrocatalytic carbon dioxide reduction (ECR) offers a sustainable solution for converting carbon dioxide into valuable chemicals and fuels, which is of great significance for achieving carbon neutrality goals. Copper-based catalysts demonstrate excellent performance in the ECR process, owing to their unique ability to promote C-C coupling reactions and generate multi-carbon products. However, catalytic performance, particularly product selectivity, is highly sensitive to the structural characteristics of copper active sites at various scales. This review systematically examines recent advances in the design of Cu-based catalysts for ECR, spanning three representative classes, i.e., single/dual-atom catalysts, nanoclusters, and nanoparticles. For each class, we summarize design strategies, such as coordination environment modulation, heteroatom doping, ligand engineering, and morphology control, and analyze their impact on product selectivity toward C1 and C2+ products. Particular emphasis is placed on the underlying structure-performance relationships and the mechanistic origins of C-C coupling. We also discuss the role of electrolyzer configurations in translating catalyst performance toward practical application. Finally, we outline major challenges and future directions for the rational design of efficient, stable, and scalable Cu-based ECR systems. This review offers strategic design principles for achieving highly selective and efficient ECR to value-added products.