The hydrogenation of CO2 to produce carbon-one fuels (such as natural gas and methanol) is the critical process of power-to-gas technology to the conversion of renewable energy and chemical energy. The development of efficient catalysts is crucial for CO2 hydrogenation. This study focuses on Ni-based catalytic systems, discusses the influence of support properties and metal particle structure, and reveals the promoting effect of surface defects and metal-support interaction. By tuning the Ni particle size and surface oxygen vacancy, the size sensitivity of Ni nanoparticles was clarified by excluding the interference of surface oxygen vacancies, and the conversion frequency of CO2 decreased with the increase of Ni particle size. By controlling the particle size of CeO2 cube, the support size effect was explored. The small particle size CeO2-supported Ni catalyst shows a high specific surface area, which promotes the Ni dispersion in a cluster structure. The Ni cluster structure forms strong Ni-CeO2 interaction, resulting in more oxygen vacancies and unique adsorption properties for reactant molecules and CO. Using the high-temperature heat treatment process, metal-support interaction in Ni/CeO2 was established. The in situ activation of catalyst by hydrogen generates suitable metal-support interaction, promotes the high dispersion of Ni nanoparticles, forms a high density of surface oxygen vacancies and a large number of weak basic sites, and enhances the catalyst ability for H2 and CO2 adsorption/activation and low-temperature CO2 methanation. In situ real-time infrared spectroscopy confirmed that formate was a key intermediate, and the CO generation over small-size Ni/CeO2 originated from the existence of surface carboxyl pathways. The catalyst stability studies show that the initial activity decreases due to the agglomeration reconstruction of Ni particles and carbon deposition on the small Ni particle size. The research provides experimental basis and theoretical guidance for the design and development of high-performance Ni-based catalysts for CO2 hydrogenation.

Structure-activity relationship and reaction mechanism in Ni-catalyzed hydrogenation of carbon dioxide

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