Why Ni/CeO2 is more active than Ni/SiO2 for CO2 methanation? Identifying effect of Ni particle size and oxygen vacancy.

An impregnated Ni/CeO 2 catalyst with an array structure and a phyllosilicate-based Ni/SiO 2 catalyst prepared by hydrothermal method were designed for CO 2 methanation. The as-synthetized Ni/SiO 2 catalyst exhibits a high Ni content of 25.9 wt%, while its CO 2 conversion at low temperature is far lower than that of Ni/CeO 2 , whose Ni content is only 10.0 wt%. TEM and XRD results show that the Ni/CeO 2 catalyst possesses very tiny Ni particle size of around 1.2 nm, which leads to large H 2 uptake capacity. XPS and Raman analyses indicate that Ni/CeO 2 obtains more oxygen vacancies resulting in promotion of the CO 2 activation. The combined effect of the Ni/CeO 2 catalyst to enhance chemisorption of H 2 and CO 2 leads to high low-temperature activity. [Display omitted] • The catalytic activity of Ni/CeO 2 and Ni/SiO 2 was compared for CO 2 methanation. • The Ni/CeO 2 catalyst possessed smaller Ni particle size and larger H 2 chemisorption capacity. • The Ni/CeO 2 catalyst exhibited more oxygen vacancies and enhanced CO 2 activation property. • Enhanced H 2 and CO 2 activation properties of Ni/CeO 2 led to higher activity. [ABSTRACT FROM AUTHOR]