Cu₂O nanoparticles with controlled surface roughness for CO₂ electroreduction towards C₂₊ products

Electrocatalytic CO₂ reduction to produce multi-carbon (C₂₊) products represents a promising avenue for carbon recycling and CO₂ conversion industrialization. However, improving C₂₊ selectivity remains challenging due to uncontrollable reaction pathways. Adjusting the surface properties of the catalyst can effectively influence the nature of the active sites and the branching of the reaction pathways. Herein, we successfully synthesized of Cu₂O catalysts with different roughness by adjusting the amount of surfactant, a structure-directing agent. The optimal catalyst indicated a remarkable FE_C2+ of 84.2 % at −1.4 V vs. RHE, with an ethylene selectivity of 56.3 % and C₂₊ partial current density of 416.4 mA/cm² in a flow cell. In-situ spectroscopy characterization and COMSOL simulations revealed that *CO intermediates tend to desorb from the rough surface, which accelerates the reduction of active sites Cu⁺ and leads to CO formation. In contrast, flat catalyst surfaces facilitate the carbon intermediate adsorption, thereby stabilizing Cu⁺ and promoting C-C coupling, ultimately enhancing C₂₊ production. This work not only refines the structure–activity relationship between catalyst surface roughness and products selectivity, but also offers strategies for designing efficient catalysts from the perspective of surface properties.