Highly Dense Cu Nanowires for Low-Overpotential CO2 Reduction

Electrochemical reduction of CO2, an artificial way of carbon recycling, represents one promising solution for energy and environmental sustainability. However, it is challenged by the lack of active and selective catalysts. Here, we report a two-step synthesis of highly dense Cu nanowires as advanced electrocatalysts for CO2 reduction. CuO nanowires were first grown by oxidation of Cu mesh in air and then reduced by either annealing in the presence of hydrogen or applying a cathodic electrochemical potential to produce Cu nanowires. The two reduction methods generated Cu nanowires with similar dimensions but distinct surface structures, which have provided an ideal platform for comparative studies of the effect of surface structure on the electrocatalytic properties. In particular, the Cu nanowires generated by electrochemical reduction were highly active and selective for CO2 reduction, requiring an overpotential of only 0.3 V to reach 1 mA/cm2 electrode current density and achieving Faradaic efficiency toward CO as high as ∼60%. Our work has advanced the understanding of the structure–property relationship of Cu-based nanocatalysts, which could be valuable for the further development of advanced electrocatalytic materials for CO2 reduction.