Au on in₂O_3-x/TiO₂(110): A Highly Active and Selective Catalyst for the Conversion of CO₂ to Methanol

Methanol production by carbon dioxide hydrogenation is a promising route for supplying industrial fuel demands, but achieving high methanol selectivity remains challenging due to competing favorable reactions. Here, we investigate model Au/In₂O_3-x/TiO₂(110) catalysts to elucidate the roles of metal-oxide and oxide-oxide interactions in CO₂ conversion. Using a combination of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), temperature-programmed desorption (TPD), and catalytic measurements, we show that small coverages of Au (<0.15 monolayer) dispersed on In₂O_3-x/TiO₂(110) significantly enhance both CO₂ and H₂ activation at low temperatures (300-400 K). The Au/In₂O_3-x/TiO₂(110) systems exhibit superior catalytic performance, with the highest methanol selectivity (∼80-85%) and increased conversion rates compared to In₂O_3-x/TiO₂(110) and Au/TiO₂(110). Spectroscopic results showed that Au nanoparticles promote the formation of oxygen vacancies and enhance CO₂ activation, without inducing the dissociation of methoxy and methanol. Reaction studies support a formate-mediated reaction pathway, distinct from the CO-mediated route observed on Au/TiO₂ catalysts that leads to very low methanol selectivity. Oxide-oxide interactions stabilized the partially reduced In₂O_3-x, and prevented Au-In alloy formation under CO₂+H₂ conditions, preserving methanol selectivity. These findings highlight the importance of synergistic metal↔oxide-oxide interactions when designing efficient catalysts for selective hydrogenation of CO₂ to methanol while minimizing the content of Au and In₂O_3-x.