Water-PromotedC–C Coupling Reaction in Plasma-CatalyticCO₂ Hydrogenation for Ethanol Production

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.