Driving Factors of Copper Surface Restructuring During Electrochemical CO2 Reduction

Copper (Cu) is a uniquely versatile catalyst whose performance in reactions, such as the electrochemical CO2 reduction reaction (CO2RR) is intimately linked to the dynamic evolution of its surface under operating conditions. Rather than remaining structurally static, Cu undergoes continuous surface restructuring, forming new morphologies, facets, and defect structures that differ significantly from the as-prepared material. These transformations strongly influence catalytic activity and selectivity, yet the mechanisms governing them remain poorly understood. As a result, Cu surface restructuring has emerged as a “black box” phenomenon in electrocatalysis, marked by contradictory interpretations and a lack of predictive control. In this review, we examine six major factors proposed to drive Cu surface restructuring: (i) adsorbed hydroxyl species, (ii) applied potential, (iii) adsorbed CO intermediates, (iv) surface oxidation, (v) electrolyte composition, and (vi) current density. We discuss how each factor can modify surface energetics, atomic mobility, and local reaction environments, while emphasizing that these influences rarely act independently.