Tunable Syngas Formation from Electrochemical CO₂ Reduction on Copper Nanowire Arrays

Producing syngas from electrochemical reduction of CO2 by renewable energy offers an opportunity to reduce CO2 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 CO2 and H2O for tunable syngas production. It is demonstrated that syngas, the mixture of H2 and CO, could be attained with a wide range of compositions (from 1:2 to 3:1) from CO2 reduction and H2O reduction on these Cu NAs in aqueous solutions. In addition, Cu NAs show a high current density, 4 mA/cm2, 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 CO2 reduction by Cu-based catalysts.