Electrochemical conversion of CO2 plasmas

Abstract

The integration of non-thermal CO₂ plasma (NTP) with a custom-designed electrolyte-gap electrolyser and CuO catalysts represents an innovative strategy to enhance the electrochemical conversion of CO₂ into C1–C3 products. Systematic galvanostatic experiments conducted at current densities ranging from 100 to 225 mA cm^-2 demonstrated that plasma-on operation significantly reduces cell voltages (by up to ~1.3 V) and that product selectivity transitions from C1 species (CO and methane) to C2+ products, including ethylene, ethanol, acetate, propylene, and propanol. While CO and H₂ predominate under plasma-off conditions, with limited formation of C2 products, the hybrid plasma–electrochemical system increases the Faradaic efficiency (FE) for ethylene up to 39.5% and ethanol up to 18.1%. These enhancements are attributed to plasma-generated reactive species (radicals and excited-state molecules) that lower kinetic barriers for C–C coupling and modify the interfacial pH, thereby reducing parasitic carbonate/bicarbonate losses. The plasma-on state resulted in a statistically significant increase in liquid product carbon efficiency (from an average of ~0.41% during plasma-off experiments to ~0.91% during plasma-on experiments). Although the system currently exhibits lower overall energy efficiency owing to the power demands of the plasma discharge, this work establishes a robust framework for flexible product tuning and sustainable carbon utilisation via plasma-activated feeds.