Effect of Atmospheric-Pressure Helium Plasma-Jet Treatment on Electrocatalysis of CO2 Reduction Reaction using Nanoporous Copper Films

Abstract

The conversion of carbon dioxide (CO2) to various clean and available fuels or energy sources is considered a promising path to alleviate global warming and energy issues. However, this reaction requires an efficient electrocatalyst with high selectivity. In this study, a nanoporous copper (NPC) film with a ligament size of 35 ± 6 nm was used as an electrocatalyst for CO2 reduction. The current density of the CO2 reduction reaction and the Faradaic efficiency (FE) of HCOOH are doubled with the use of NPC as an electrocatalyst compared to that of copper (Cu) foils. The helium (He) plasma-jet treatment on NPC film catalysts can further enhance the CO2 reduction reaction rate and the selectivity of HCOOH. XPS results reveal that He plasma-jet treatment of the NPC film can change the surface activity of Cu in terms of the oxide content and hydrophilic groups. In addition, the hydrophilicity of the NPC film is confirmed through water contact angle tests; it decreases from 133.64° to 21.57° after He plasma-jet treatment. He plasma-jet treatment brings about the decomposition of Cu–O and the presence of O–C=O functional groups which facilitate the reduction of CO2 to HCOOH.