Water-Promoted C–C Coupling Reaction in Plasma-Catalytic CO₂ Hydrogenation for Ethanol Production

Abstract

The conversion of CO2 into alcohols has attracted widespread interest. Herein, we present an approach for the plasma-catalytic CO2 hydrogenation to ethanol over a Cu2O/CeO2 catalyst under atmospheric pressure at a low temperature of ∼75 °C. The Cu2O/CeO2 catalyst initially exhibits low ethanol selectivity (2.1%), which dramatically increases to 56% (78% total alcohols selectivity) with the assistance of water. D2O and H218O isotope-tracing experiments reveal the partial decomposition of water and the active involvement of its derivatives in the multistep pathway for ethanol synthesis. The multiple roles of H2O in switching alcohols production from methanol to ethanol are investigated. The plasma-generated OH in both adsorbed and radical states promotes C–C coupling via CO-H2CO bonding and facilitates hydrogenation through proton transfer. Additionally, the presence of adsorbed H2O and OH enhances the desorption of ethanol, further enhancing alcohol selectivity. It is envisaged that these findings would inspire value-added transformation of CO2 to produce higher alcohols and pave the way for efficient chemical processes.