Selective Conversion of CO ₂ to Methanol on a In ₂ O _{3– x} –TiO ₂ (110) Interface: Importance of Oxide–Oxide Interactions

Methanol is a strategic energy vector for the storage and delivery of energy and is a widely used precursor for the synthesis of many high-value chemicals. The hydrogenation of carbon dioxide (CO 2 ) into methanol is a key process in industrial operations. In this study, we show that an oxide–oxide interface generated by a low loading (0.15 ML) of In 2 O 3– x on a TiO 2 (110) substrate has a high activity and selectivity as a catalyst for the CO 2 + 3H 2 → CH 3 OH + H 2 O process. The properties of the In 2 O 3– x –TiO 2 interface under reaction conditions were investigated using a combination of synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS), temperature-programmed desorption (TPD), and catalytic testing. The In 2 O 3– x overlayer spread out on top of the titania and was rich in defects and O vacancies that activated CO 2 and H 2 as reactants, without destroying CH 3 O and CH 3 OH as reaction products. The In 2 O 3– x /TiO 2 (110) catalyst is at least 1 order of magnitude more active than bulk indium oxide while maintaining a very high selectivity (∼80%) toward methanol production. Under the rich hydrogen environment of methanol synthesis, the oxide–oxide interactions allowed only a partial reduction of the In cations, preventing the formation of metal alloys as seen in the case of catalysts with metal–indium oxide interfaces. Thus, the dispersion of low loadings of In 2 O 3– x on a stable oxide substrate is a valid and low-cost approach for generating efficient catalysts for CO 2 valorization.