Recent Advances of Indium Oxide-Based Catalysts for CO 2 Hydrogenation to Methanol: Experimental and Theoretical.

Methanol synthesis from the hydrogenation of carbon dioxide (CO 2 ) with green H 2 has been proven as a promising method for CO 2 utilization. Among the various catalysts, indium oxide (In 2 O 3 )-based catalysts received tremendous research interest due to the excellent methanol selectivity with appreciable CO 2 conversion. Herein, the recent experimental and theoretical studies on In 2 O 3 -based catalysts for thermochemical CO 2 hydrogenation to methanol were systematically reviewed. It can be found that a variety of steps, such as the synthesis method and pretreatment conditions, were taken to promote the formation of oxygen vacancies on the In 2 O 3 surface, which can inhibit side reactions to ensure the highly selective conversion of CO 2 into methanol. The catalytic mechanism involving the formate pathway or carboxyl pathway over In 2 O 3 was comprehensively explored by kinetic studies, in situ and ex situ characterizations, and density functional theory calculations, mostly demonstrating that the formate pathway was extremely significant for methanol production. Additionally, based on the cognition of the In 2 O 3 active site and the reaction path of CO 2 hydrogenation over In 2 O 3 , strategies were adopted to improve the catalytic performance, including (i) metal doping to enhance the adsorption and dissociation of hydrogen, improve the ability of hydrogen spillover, and form a special metal-In 2 O 3 interface, and (ii) hybrid with other metal oxides to improve the dispersion of In 2 O 3 , enhance CO 2 adsorption capacity, and stabilize the key intermediates. Lastly, some suggestions in future research were proposed to enhance the catalytic activity of In 2 O 3 -based catalysts for methanol production. The present review is helpful for researchers to have an explicit version of the research status of In 2 O 3 -based catalysts for CO 2 hydrogenation to methanol and the design direction of next-generation catalysts.