Preparation of Supported ZnCoOx Catalysts and Investigation of Their CO2 Methanation Performance

The type of carrier plays a regulatory role in the physicochemical properties of the catalyst: The support not only determines the extent of interaction between metallic Co (Co0) and the metal oxide, but also influences the degree of reduction of the ZnCoOx catalyst, the dispersion of Co0, and the total number of weak and moderately strong basic sites on the catalyst surface. The results of the activity evaluation indicate that the ZnCoOx/CeO2 catalyst exhibits the highest catalytic activity, with a CO2 conversion rate of 57.4% and a methane yield of 557.2 mg·gcat-1·h-1 at 2 MPa; furthermore, the methane selectivity of all catalysts exceeded 97.5%.

Analysis of the correlation between structure and performance indicates that the unique Ce4+/Ce3+ redox cycle of CeO2 and strong metal–support interactions are key to the enhanced performance. During the experiment, Co0 was responsible for hydrogen dissociation, whilst oxygen vacancies at the interface activated CO2, with the two working in synergy to efficiently catalyse the CO2 methanation reaction.