Producing syngas from electrochemical reduction of CO 2 by renewable energy offers an opportunity to reduce CO 2 emissions and provide chemicals and fuels. Herein, we report the careful manipulation of the reduction treatment to synthesize copper nanowire arrays (Cu NAs). By thermal oxidation, copper oxide nanowires were grown on a Cu mesh. Then, thermal reduction and electrochemical reduction were used to reduce copper oxide to Cu with the morphologic features largely preserved. The derived Cu NAs are cost-effective electrocatalysts capable of reducing CO 2 and H 2 O for tunable syngas production. It is demonstrated that syngas, the mixture of H 2 and CO, could be attained with a wide range of compositions (from 1:2 to 3:1) from CO 2 reduction and H 2 O reduction on these Cu NAs in aqueous solutions. In addition, Cu NAs show a high current density, 4 mA/cm 2 , at a low potential, −0.5 V, with a high syngas faradaic efficiency of over 70%. This approach explores a new method that sheds light on tuning the syngas composition from the electrochemical CO 2 reduction by Cu-based catalysts.

The electrochemical conversion of carbon dioxide (CO2) into gaseous or liquid fuels has the potential to store renewable energies and reduce carbon emissions. Here, we report a three-step synthesis using Cu–Ag bimetallic nanowire arrays as catalysts for electrochemical reduction of CO2. CuO/Cu2O nanowires were first grown by thermal oxidation of copper mesh in ambient air and then reduced by annealing in the presence of hydrogen to form Cu nanowires. Cu–Ag bimetallic nanowires were then produced via galvanic replacement between Cu nanowires and the Ag+ precursor. The Cu–Ag nanowires showed enhanced catalytic performance over Cu nanowires for electrochemical reduction of CO2, which could be ascribed to the incorporation of Ag into Cu nanowires leading to suppression of hydrogen evolution. Our work provides a method for tuning the selectivity of copper nanocatalysts for CO2 reduction by controlling their composition.

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