Morphology Effect of La2O2CO3 on CO2 Methanation over Ni-Based Catalysts

CO 2 methanation is regarded as an efficient method for upgrading CO 2 to fuels and reducing environmental impacts of greenhouse gas emission. In this study, we developed Ni/ La 2 O 2 CO 3 low temperature CO 2 methanation catalysts by tuning the metal-support interaction via changing the morphology of catalyst supports. La 2 O 2 CO 3 supports with various morphologies including nanotriangles (La 2 O 2 CO 3 -T), nanorods (La 2 O 2 CO 3 -R), and nanoparticles (La 2 O 2 CO 3 -P), were synthesized as the supports of Ni catalysts for CO 2 methanation reaction. The CO 2 methanation performance of the synthesized Ni/La 2 O 2 CO 3 catalysts was found to be markedly superior to that of conventional Ni/SiO 2 catalysts with the following orders: Ni/La 2 O 2 CO 3 -T > Ni/La 2 O 2 CO 3 -R > Ni/La 2 O 2 CO 3 -P > Ni/SiO 2 . In the comparative characterization of Ni/La 2 O 2 CO 3 catalysts with various morphologies, TEM and H 2 -TPR results reveal that the Ni/La 2 O 2 CO 3 -T catalysts exhibit better dispersion of Ni nanoparticles and higher reducibility. Moreover, X-ray photoelectron spectroscopy (XPS), O 2 and H 2 temperature programmed desorption (O 2 -TPD, H 2 -TPD) results indicate that the Ni/La 2 O 2 CO 3 -T catalysts possess a lower oxygen vacancy formation energy leading to a higher concentration of interfacial oxygen vacancies, which enhances the adsorption hydrogen at these interfacial oxygen vacancy sites. CO 2 -TPD results further reveal that Ni/La 2 O 2 CO 3 -T catalysts own higher concentration of medium basic sites, which promote the adsorption and activation of CO 2 . Consequently, Ni/La 2 O 2 CO 3 -T catalysts demonstrate superior low-temperature CO 2 methanation activity by hydrogenation of CO 2 adsorbed as surface carbonates on the La 2 O 2 CO 3 surfaces with hydrogen spilled over from the Ni surfaces via the interfacial oxygen vacancies to the catalyst support. Graphical Abstract