Electrocatalytic reduction of CO2 is crucial for environmental sustainability and renewable energy storage, with Cu-based catalysts excelling in producing high-value C2+ products. However, a comprehensive analysis of how specific electrolyte influences Cu-based catalysts is lacking. This review addresses this gap by focusing on how electrolytes impact surface reconstruction and the CO2 reduction process on Cu-based electrocatalysts, identifying specific electrolyte compositions that enhance the density and stability of active sites, and providing insights into how different electrolyte environments modulate the selectivity and efficiency of C2+ product formation. The review begins by exploring how electrolytes induce favorable surface reconstruction in Cu-based catalysts, affecting surface roughness through dissolution-redeposition of Cu species and interactions with halogens and molecular additives. It also covers changes in crystalline facets of Cu and Cu2O, and oxidation states, highlighting transitions from Cu0 to Cuδ+ and the stabilization of Cu+. The role of electrolytes in the C–C coupling process is examined, emphasizing their effects in modulating mass and charge transfer, CO2 adsorption, intermediate evolution, and product desorption. Subsequently, the mechanisms by non-aqueous electrolytes, including organic solvents, ionic liquids, and mixed electrolytes, affecting CO2 reduction are analyzed, highlighting the unique advantages and challenges of each type. The review concludes by addressing current challenges, proposing solutions, and research directions, such as optimizing electrolyte composition by integrating diverse cations and anions and employing advanced in-situ characterization techniques. These insights can significantly enhance CO2 reduction performance on Cu-based electrocatalysts, advancing efficient and sustainable green energy technologies.
