Photothermal catalytic synthesis of DMC from CO2 and CH3OH at atmospheric pressure: Synergistic effect of surface hydroxyl groups and oxygen vacancies on spindle-like CeO2-x

Abstract

The light-driven conversion of CO₂ to dimethyl carbonate (DMC) represents a promising green and sustainable pathway for achieving dual-carbon goals. However, the inherent difficulty in activating CO₂ molecules results in low DMC yields when synthesizing DMC from CO₂ and methanol (CH₃OH) under light-driven conditions. In this study, the activation of CO₂ and CH₃OH is enhanced by modulating the number of hydroxyl groups and the concentration of oxygen vacancies on the surface of spindle-like CeO_2-x through the introduction of cetyltrimethylammonium bromide (CTAB). Photothermal catalytic experiments show that the optimal CTAB-modified CeO_2-x achieves excellent DMC yield of 5.26 mmol·g⁻¹ under mild conditions (0.1 MPa, 120℃). The X-ray photoelectron spectroscopy and CO₂ temperature-programmed desorption results demonstrate that CTAB modification increases the number of hydroxyl groups and oxygen vacancies on the CeO_2-x surface, which improves the effective activation of CO₂ to form the reactive intermediates such as *HCO₃^– and *CO₂. Notably, the increased hydroxyl groups promote the dissociation of CH₃OH into *CH₃O. Meanwhile, isotopic labeling and in situ infrared characterization confirm the light-driven reaction pathway of CO₂ and CH₃OH, involving the oxidation of CH₃OH to *CH₂OH via photogenerated holes, followed by rapid coupling with *CO₂ to generate the reactive intermediate (CH₃OCOO*). These findings provide new insights into the rational design and construction of CeO₂-based catalysts to achieve high yields of DMC under mild conditions.