Defect-Promoted Catalytic Conversion of Carbon Monoxide to Methanol on ThO₂ Surfaces

The conversion of carbon monoxide (CO) to methanol (CH₃OH) is an attractive process as it converts a toxic and environmentally harmful gas into a widely used industrial chemical via hydrogenation. Traditionally, this process is catalyzed by Cu-based multicomponent materials, which require high pressures and temperatures, making the process costly and environmentally unfriendly. In this article, we show that thorium dioxide (ThO₂) is an attractive alternative catalyst that is earth abundant and chemically and thermally stable. Using quantum chemistry calculations based on density functional theory (DFT), we investigated the feasibility and reaction mechanism of the CO-to-CH₃OH conversion catalyzed by the ThO₂ (111) surface. Particular focus is given to the role of O vacancies. It is found that that the O vacancies act as catalytic centers, promoting the chemical activation of CO and H₂ simultaneously and facilitating the reaction steps to form CH₃OH. Based on these observations, we propose a dual-site catalytic mechanism wherein oxygen vacancies activate CO and H₂ in parallel. This work demonstrates that the presence of O vacancies on the ThO₂ surface improves its catalytic performance, paving the way for broader application of ThO₂ catalysis to sustainable chemistry.