(513ac) Indium Oxide Catalysts for CO2 Hydrogenation to Methanol: Role of Support in the Activity and Selectivity

The excessive emissions of carbon dioxide (CO₂) from human activities, especially the burning of fossil fuels, have led to severe consequences in the environment. To mitigate its harmful impact, one of the most attractive strategies is CO₂ utilization by selective reduction into value-added chemicals such as methanol. The key to realize the targeted CO₂ conversion is the development of highly efficient catalysts. Currently, Cu/ZnO/Al₂O₃ ternary catalysts are used for industrial methanol synthesis from syngas (CO/CO₂/H₂). However, the low selectivity and poor structural stability under operation conditions has limited their applications in direct CO₂ hydrogenation to methanol. As an alternative, indium oxide (In₂O₃) and its metal alloys have been reported to exhibit high selectivity and excellent stability in methanol production from CO₂ hydrogenation. Notably, the performances of In₂O₃ catalysts could be drastically affected by the supporting material, the origin of which, however, remains elusive. In this work, we have systematically investigated the role of support (ZrO₂, CeO₂ and Pr₆O₁₁) in determining the activity and selectivity of In₂O₃ catalysts for CO₂ hydrogenation under ambient pressure. The strucutral and surface properties of these catalysts before and after reaction were characterized by a suite of techniques including XRD, N₂ adsorption, TEM, TPR, CO₂-TPD and in situ XPS. DFT modelling and in situ DRIFTS were also performed to account for the substrate effect on the formation of oxygen vacancies and reaction mechanism in CO₂ hydrogenation. The role of support in the catalytic behavior of In₂O₃ catalysts is discussed based on experimental and theoretical results and has been correlated with its susceptibility to CO₂ activation and formation of oxygen vacancies.