Understanding defect generation on CeO2 and its utilization for enhanced metal-support interactions in Ni/CeO2 catalysts for improved CO2 methanation performance

Abstract

A series of CeO 2 supports were treated in an N 2 plasma before being impregnated with Ni precursors to evaluate the impact this has on the metal-support interface and catalytic performance. This impact was determined using a suite of characterization methods including X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2 -TPR), ex situ and in situ X-ray absorption spectroscopy (XAS) and in situ Kerr-gated Raman. The combined and self-consistent results indicated that plasma treatment of CeO 2 can lead to the generation of an increasing number of oxygen vacancies, and a loss of long-range order in samples treated for 1 h, realizing a highly defective CeO x film at the interface between the Ni metal nanoparticles and the bulk CeO 2 . However, this highly defective CeO x surface significantly enhances the Ni-CeO x interaction, resulting in a number of smaller Ni NPs in intimate contact with the support, leading to improved catalytic performance for CO 2 methanation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the more defect-dense Ni−CeO x interface leads to the formation of more bidentate bridged carbonates (vs. bidentate chelate) and which are more readily consumed during reaction, suggesting the identification of an important parameter to effect low-temperature (< 300 °C) CH 4 production. • A defective and poorly crystalline CeO 2 surface has been generated after a N 2 plasma treatment at room temperature • The strong anchoring of smaller Ni nanoparticles on the defective CeO x surface facilitates charge transfer and oxygen spillover in Ni/CeO 2 • A significantly improved catalytic activity in CO 2 methanation is observed due to the enhanced Ni-CeO x interaction. • Bidentate bridged carbonates, which is more reactive than bidentate chelate carbonates, are formed for superior CO 2 methanation activity