Indium-Promoted ZnZrOx Solid Solution Catalyst for CO2 Hydrogenation to Methanol

Methanol synthesis is one of the most important and industrially viable approaches to carbon dioxide (CO2) utilization. Both the ZnZrOx (ZZO) solid solution catalyst and the In2O3 catalyst have garnered extensive attention for their high methanol selectivity and excellent resistance to sintering and sulfur in CO2 hydrogenation. Herein, a ZZO solid solution with a large surface area is selected as the carrier, and the supported In2O3 strongly interacts with the ZZO to boost the generation of more oxygen vacancies on the ZZO surface that catalyzes methanol production. On incorporating an appropriate amount of In2O3 (In 2.5 wt %) onto the ZZO catalyst, In2.5/ZZO exhibits markedly enhanced methanol production with a CO2 conversion rate of 13.5% and a methanol space-time yield of 0.749 g gcat–1 h–1 at 330 °C, 5 MPa, and 24,000 mL gcat–1 h–1. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveals that the incorporated indium species facilitate hydrogen activation to increase the availability of surface hydrogen. The surface hydrogen is transferred to the active sites due to hydrogen spillover, facilitating the formation of HCOO* intermediates and boosting the hydrogenation of CO2 to methanol. Theoretical analysis allows the rationalization of the observed improvement in the catalytic performance of the In2.5/ZZO catalyst. In2.5/ZZO showed excellent stability for up to 200 h on stream, demonstrating its potential as a practical catalyst for the hydrogenation of CO2 to methanol.