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

Abstract

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.