Interfacial synergistic catalysis over Ni nanoparticles encapsulated in mesoporous ceria for CO2 methanation

Abstract

An ordered mesoporous ceria, mpCeO2, was synthesized using nanocasting, followed by strong electrostatic adsorption to prepare Ni nanoparticles encapsulated in mpCeO2 for CO2 methanation. At 225 °C, TOF of Ni/mpCeO2 catalyst (0.183 s−1) is 3 times higher than that of Ni catalyst supported on conventional CeO2 prepared by the same method (0.057 s−1). Characterization results indicate that encapsulated structure provides rich Ni-CeO2 interface with more oxygen vacancies, playing a key role in CO2 activation. As evidenced by in-situ DRIFTS experiments, CO2 activation over Ni/mpCeO2 catalyst occurs through combined associative and dissociative mechanisms. Moreover, small and highly dispersed Ni nanoparticles in channels of mpCeO2 facilitate H2 dissociation, supplying sufficient *H for CO hydrogenation with *HCO intermediate species and leading to high CH4 selectivity. In addition to enhanced low-temperature activity and selectivity, Ni/mpCeO2 catalyst is very stable throughout 70 h since metal sintering can be inhibited by confinement effect of mesoporous structure.