Tailoring the Valence of Cobalt via Indium Addition for Promoting CO ₂ Hydrogenation to Ethanol

The hydrogenation of CO2 to value-added chemicals and fuels represents a promising strategy for CO2 utilization; however, the rational design of highly active catalysts for multicarbon products like ethanol remains a major challenge. This work demonstrates that indium (In) promotion effectively modulates the cobalt valence state in CoInZr catalysts, resulting in a remarkable enhancement in ethanol selectivity. A series of CoInZr-x catalysts were synthesized via coprecipitation, with the optimized CoInZr-0.7 catalyst achieving a CO-free ethanol selectivity of 24.9% at a CO2 conversion of 11.1% at 300 °C and 5 MPa, showing approximately a 20-fold increase over the reference unpromoted CoZr catalyst (1.1%). Comprehensive characterization (X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), H2-TPR, and CO/CO2-TPD) collectively demonstrates that In2O3 incorporation modulates the electronic structure of cobalt, inhibits its over-reduction, and stabilizes Coδ+ species, leading to the formation of synergistic Co0–Coδ+ active pairs. In situ DRIFTS studies identified formate and molecularly adsorbed *CO as key surface intermediates. It is revealed that the Co0–Coδ+ interface effectively balances dissociative and nondissociative CO activation, thereby suppressing excessive hydrogenation to methane while promoting C–C coupling for ethanol production. This work highlights the efficacy of indium promotion in tailoring cobalt valence states to steer CO2 hydrogenation toward valuable oxygenates.