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 CH 3 OH with CO 2 presents broad prospects in CO 2 conversion to value-added products, while the underlying reaction mechanism over the catalysts with oxygen vacancy (O v ) active centers has not been clearly revealed yet. Herein, we report O v structures fabricated on CeO 2 nanorods via a facile element doping route (denoted as M x Ce 1– x O 2, x = 0, 0.05, M including Ca, Co, Fe, and Mn), and O v -enriched Fe 0.05 Ce 0.95 O 2 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, H 2 -TPR, Raman, and XPS measurements show the promotion effect of element doping into the CeO 2 nanorods on the formation of the surface oxygen vacancies (O v ). CO 2 -TPD and in situ FT-IR of adsorbed methanol demonstrate that oxygen vacancies and an adjacent acidic site over M x Ce 1– x O 2 can effectively activate and convert CO 2 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 O v and a neighboring acidic site is responsible for the promising DMC synthesis activity over the M x Ce 1– x O 2 nanorods. The identification of the active sites of the oxidized O v species in this system will potentially guide the design of an efficiently heterogeneous catalyst for CO 2 chemical conversion.