Regulation of Surface Oxygen Vacancies on Ce-Based Catalysts for Dimethyl Carbonate Direct Synthesis from CO2 and CH3OH

Achieving dimethyl carbonate (DMC) direct synthesis from the reaction of CH3OH with CO2 presents broad prospects in CO2 conversion to value-added products, while the underlying reaction mechanism over the catalysts with oxygen vacancy (Ov) active centers has not been clearly revealed yet. Herein, we report Ov structures fabricated on CeO2 nanorods via a facile element doping route (denoted as M x Ce1–x O2, x = 0, 0.05, M including Ca, Co, Fe, and Mn), and Ov-enriched Fe0.05Ce0.95O2 presents a significantly higher methanol conversion (63.7%) and a DMC generation rate up to 802.8 mmol g–1 h–1 with a DMC selectivity (93.0%) among these catalysts, reaching the highest level compared with previously reported catalyst systems for the generation of DMC. HR-TEM, H2-TPR, Raman, and XPS measurements show the promotion effect of element doping into the CeO2 nanorods on the formation of the surface oxygen vacancies (Ov). CO2-TPD and in situ FT-IR of adsorbed methanol demonstrate that oxygen vacancies and an adjacent acidic site over M x Ce1–x O2 can effectively activate and convert CO2 to long-chain chemicals. In situ FT-IR further confirms that the promoted formation of the carbonic acid monomethyl ester (the key reaction intermediate) via the cooperation of Ov and a neighboring acidic site is responsible for the promising DMC synthesis activity over the M x Ce1–x O2 nanorods. The identification of the active sites of the oxidized Ov species in this system will potentially guide the design of an efficiently heterogeneous catalyst for CO2 chemical conversion.