CO2 Hydrogenation to Methanol on Indium Oxide-Supported Rhenium Catalysts: The Effects of Size

In this work, CO2 hydrogenation over In2O3-supported rhenium (Re) catalysts was found to be highly size-dependent. When the Re loading was less than 1 wt %, the strong interaction between Re and In2O3 caused atomically dispersed Re species with a positive charge, resulting in high activity for CO2 hydrogenation to methanol with enhanced stability at elevated temperatures. The space-time yield of methanol over the 1 wt % Re/In2O3 catalyst reached 0.54 g(MeOH) g(cat)(-1) h(-1) with a methanol selectivity of 72.1% at 5 MPa and 573 K. With increasing Re loading, the In2O3 supported Re catalysts become more favored for CO2 methanation. Under the same experimental conditions, the methane selectivity is close to 100.0% over the 10 wt % Re/In2O3 catalyst. Catalyst characterizations and density functional theoretical (DFT) calculations further confirm that the size of the Re/In2O3 catalyst has a significant effect on hydrogen activation and the selectivity of the CO2 hydrogenation reaction. Due to the strong Re-In2O3 interaction, the atomically dispersed Re in the In2O3 surface lattice not only stabilizes oxygen vacancies but also results in H delta+ formation upon hydrogen adsorption. This significantly promotes methanol synthesis from CO2 hydrogenation. Meanwhile, the 10 wt % Re/In2O3 catalyst with supported Re nanoclusters induces H delta- formation, which eventually leads to more methane production. The present study demonstrates the atomically dispersed Re/In2O3 catalyst is promising for CO2 hydrogenation to methanol.

Automated summary

In this study, the size of In2O3-supported rhenium (Re) catalysts was found to significantly impact the CO2 hydrogenation reaction. Atomically dispersed Re species with a positive charge on the Re/In2O3 catalyst surface showed high activity and stability for CO2 hydrogenation to methanol, while the presence of Re nanoclusters favored methane production. Catalyst characterization and theoretical calculations confirmed the influence of catalyst size on hydrogen activation and the selectivity of the CO2 hydrogenation reaction.