Design of CeO2-supported LaNiO3 perovskites as precursors of highly active catalysts for CO2 methanation

Abstract

This work investigates the viability of 10–50% LaNiO₃/CeO₂ formulations, prepared by combined citric acid and impregnation methods, as precursors of highly active and stable materials for CO₂ methanation. The prepared materials were widely characterized before and after the controlled reduction process. XRD and STEM-EDS mapping analysis confirmed the ex-solution of Ni NPs during reduction of LaNiO₃/CeO₂ formulations, leading to Ni–La₂O₃/CeO₂ formation. Low LaNiO₃ loading favored the ex-solution of small-sized Ni NPs (<5 nm) highly dispersed over CeO₂ and La₂O₃ surfaces. H₂-TPR experiments revealed that the higher reducibility of the samples prepared with low LaNiO₃ loading promoted the H₂ activation at lower temperatures. XPS experiments suggest that this promotion is due to the higher accessibility of Ni as well as Ni–ceria interaction. The material obtained after the reduction of the 10% LaNiO₃/CeO₂ formulation shows a higher concentration of weak–medium basic sites due to a higher accessibility of Ni NPs, La₂O₃ phase and Ni–CeO₂ interface. The easier hydrogenation of CO₂ adsorbed on these basic sites, together with the promoted H₂-activation, maximized the CO₂ methanation in the kinetically controlled region for this catalyst up to 71%. The intensification of Ni, La₂O₃ and CeO₂ interactions also enhanced the CO₂ methanation efficiency and the stability of the conventional 8.5% Ni/CeO₂ catalyst. Thus, the 10% LaNiO₃/CeO₂ precursor emerges as a novel formulation to obtain highly active, selective and stable catalysts for CO₂ methanation.