Niobium Modification of CeO₂ Tuning Electron Density of Nickel–Ceria Interfacial Sites for Enhanced CO₂ Methanation

Abstract

CO 2 methanation has attracted considerable attention as a promising strategy for recycling CO 2 and generating valuable methane. This study presents a niobium-doped CeO 2 -supported Ni catalyst (Ni/NbCe), which demonstrates remarkable performance in terms of CO 2 conversion and CH 4 selectivity, even when operating at a low temperature of 250 °C. Structural analysis reveals the incorporation of Nb species into the CeO 2 lattice, resulting in the formation of a Nb−Ce−O solid solution. Compared with the Ni/CeO 2 catalyst, this solid solution demonstrates an improved spatial distribution. To comprehend the impact of the Nb−Ce−O solid solution on refining the electronic properties of the Ni−Ce interfacial sites, facilitating H 2 activation, and accelerating the hydrogenation of CO 2 * into HCOO*, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and density functional theory (DFT) calculations were conducted. These investigations shed light on the mechanism through which the activity of CO 2 methanation is enhanced, which differs from the commonly observed CO* pathway triggered by oxygen vacancies (O V ). Consequently, this study provides a comprehensive understanding of the intricate interplay between the electronic properties of the catalyst's active sites and the reaction pathway in CO 2 methanation over Ni-based catalysts.