Controllable modification of the Inδ+–Ov interface on In2O3 for efficient carbon dioxide hydrogenation to methanol†

Abstract

As is well known, catalytic performance is closely related to the interfacial properties of the catalysts, but these properties are difficult to regulate precisely and simultaneously, including the metal states, acid-basic sites, defects and so on. In this work, the interfacial properties of In₂O₃ are controllably modified through different synthetic methods, in which the metastable In^δ+ (2 < δ < 3) is mainly introduced by hydrothermal preparation, and oxygen vacancies (O_v) are produced due to the heating-induced phenomenon during N₂ calcination. In this situation, the massive formation of In^δ+ species further contributes to the formation of abundant oxygen vacancies and basic sites. More oxygen vacancies will lead to the strong adsorption of CO₂ on the surface of In₂O₃, while the basic sites benefit the generation of formic acid intermediates during the reaction process. Therefore, the formation of abundant In^δ+–O_v interfaces in H–In₂O₃–N₂ facilitate the dehydrogenation of CO₂ to methanol with high conversion and selectivity; the highest methanol spatiotemporal yield of 0.46 g_CH3OH g_cat⁻¹ h⁻¹ is obtained, which is 4.6 times higher than that of C–In₂O₃–N₂ with fewer In^δ+–O_v interfaces. This method of controllable modification of the In^δ+–O_v interface in In₂O₃ catalyst also provides valuable insight for other metal oxide catalysts for CO₂ hydrogenation to methanol.