Synergy of Cu(I) and oxygen vacancies in CO 2 hydrogenative coupling to ethanol on Cu/CeO 2− x catalysts

Hydrogenative coupling of CO₂ to ethanol presents a sustainable pathway for carbon neutralization, yet the fundamental active sites and reaction pathway/mechanism remain unclear. Here, we investigate CO₂ hydrogenative coupling over Cu/CeO₂₋ₓ catalysts, achieving an optimal CO₂ conversion of ~5% and ethanol selectivity of ~95% under 30 atm, H₂/CO₂ = 3, at 240 °C, and GHSV = 120 ml·gcat⁻¹·h⁻¹. We reveal that both Cu(I) and oxygen vacancies (Ov) serve as active sites, with turnover frequencies (TOFs) of 0.23 h⁻¹ per Ov site and 3.97 h⁻¹ per Cu(I) site, respectively. We also concluded that neither Cu(I) nor Ov can function independently; both Cu(I) and Ov are required for CO₂ activation and ethanol formation. Operando FTIR and DFT calculations identify CH₂OH* and CH₂* as key intermediates in the C-C coupling step. These findings establish a mechanistic framework for CO₂ hydrogenative coupling and provide valuable insights for designing more efficient catalysts for ethanol synthesis from CO₂ conversion.