Preparation and characterization of a highly dispersed Ru/CeZrO2 catalyst for CO2 methanation with improved activity†

Abstract

CO₂ hydrogenation to methane has drawn increasing interest in recent years. Significant efforts are being made to find a catalyst with superior catalytic performance at low temperatures. In this work, a highly dispersed Ru/CeZrO₂ catalyst with a Ce/Zr molar ratio of 4/1 was prepared via the decomposition of a ruthenium precursor by energetic species (such as electrons and radicals) from a dielectric barrier discharge (DBD) plasma, operated at about 150 °C. This was followed by thermal hydrogen reduction, resulting in dramatically enhanced activity and stability. For instance, at 275 °C, the methane formation rate on the plasma-decomposed catalyst was found to be about twice that of the catalyst prepared by the thermal decomposition of ruthenium precursor. The plasma-decomposed catalyst exhibited higher dispersion of Ru nanoparticles, enhanced electronic metal–support interactions and improved hydrogen dissociation ability, further facilitating hydrogen spillover from Ru to the surface of CeZrO₂ support. Thus, the plasma decomposition caused more surface oxygen vacancies, providing additional adsorption sites for CO₂. Analyses via in situ diffuse reflectance infrared Fourier transform spectroscopy revealed that CO₂ methanation followed the HCOO* and CO* routes on both catalysts, while the plasma decomposition treatment mainly facilitated catalytic performance at low temperatures by accelerating the formation and consumption of HCOO* in the formate route.