Role of Zirconia in Indium Oxide-Catalyzed CO2 Hydrogenation to Methanol

Monoclinic zirconia has been uncovered as a carrier able to substantially boost the activity of indium oxide for CO2 hydrogenation to methanol. Here, electronic, geometric, and interfacial phenomena associated with this peculiar effect are investigated. Generating mixed In–Zr oxides by coprecipitation does not improve performance, excluding a primary role of electronic parameters. Because even only 1 mol % of indium stabilizes the metastable tetragonal phase of zirconia, the relevance of its crystalline structure is explored in impregnated solids. Both tetragonal and monoclinic ZrO2 permit epitaxial growth of In2O3, but a more pronounced lattice mismatching leads to a lower dispersion of the oxide on the second, which is observed in the form of subnanometric islands on the carrier, and to more pronounced tensile forces. The latter triggers the formation of a surplus of oxygen vacancies only in this system, which is in line with its greatly enhanced indium-specific activity. Hence, a deposition synthesis m...