Progress in reaction mechanisms and catalyst development of ceria-based catalysts for low-temperature CO2 methanation.

With the development of carbon dioxide (CO2) capture, storage and utilization (CCSU) technologies, CO2 has gradually become a desired feedstock for the production of value-added chemicals like methane (CH4). Ceria (CeO2)-based catalysts have gained much attention because of their potential to efficiently hydrogenate CO2 to CH4 under mild conditions. Here we systematically outline the advances in CeO2-based catalysts for CO2 methanation mainly from the perspective of mechanism investigation and catalyst development. Various in situ/operando and ex situ technologies have verified that active metal and oxygen vacancies at the metal/metal oxide–CeO2 interface act as the prime active sites to promote the formation and hydrogenation of key intermediates during the CO2 methanation reaction. Kinetic analysis and in situ DRIFT characterization combined with theoretical calculations revealed that the reaction mechanism toward CO2 methanation is sensitive to active sites, and the formate route versus the carboxyl (CO*) route has been widely detected as the main methanation pathway over CeO2-based catalysts. Additionally, mainstream strategies to improve CeO2-based catalysts include optimizing reducibility, adjusting the distribution of basic sites, dispersing active metal supported on CeO2, and increasing the amount of oxygen vacancies or additional active sites for CO2 adsorption and selective hydrogenation into CH4. Finally, perspectives on the deeper understanding of active sites and intermediates' evolution and the challenges of CeO2-based catalysts for CO2 methanation in future investigations are presented. [ABSTRACT FROM AUTHOR]