Electrochemical CO₂ reduction to gaseous methane and carbon monoxide using plasma-synthesized copper nanowires

There is a growing interest among environmental researchers to synthesize a sustainable catalyst for CO₂ conversion process. Copper and modified copper offer a wide window for such catalysts. In this study, we report the use of plasma-treated copper/copper oxide nanowires for electrochemical CO₂ reduction for the first time. Plasma-treated Cu nanowires (CuO–P NWs) were comparatively evaluated with bulk copper surface in CO₂ saturated test solutions, namely, KHCO₃, KCl, and NaCl, with 0.1 and 1 M concentrations. CuO–P NWs demonstrate 50% increase in selectivity towards CO₂ reduced gaseous products (CO and CH₄) at a higher applied potential of − 1.1 V vs reversible hydrogen electrode. This increased selectivity is associated with decreased binding energy of the intermediate species on plasma-treated nanowires compared to bulk surface. Both CO and CH₄ were the main products detected in the gaseous state, and CO is suggested as the main intermediate species. The effects of different cations and anions and their concentrations in the solutions were also analyzed. It was observed that dilute solutions in 0.1 M are optimal for electrochemical CO₂ reduction (ECO₂R) and that hydration energy of cations plays a significant role in ECO₂R selectivity, while hydrogen evolution reaction was the competing reaction.