High-dispersed CeOx species on mesopores silica to accelerate Ni-catalysed CO2 methanation at low temperatures

Abstract

CO2 methanation is a key step in the power-to-gas technology for storing and distributing renewable energy as energy vectors. Due to thermodynamic constraints, highly active catalysts below about 300 °C are necessary. We demonstrate that their preparation is possible by supporting Ni nanoparticles over highly dispersed CeOx species decorating mesopores silicate (mSiO2) obtained by a template-free method. The CeOx decorated mSiO2 exhibits a 3-fold increase in activity and enhanced CH4 selectivity (98.7 % at 300 °C) compared to the Ni/mSiO2 catalyst. The performances are superior compared to the literature data. A systematic characterisation by physisorption, XPS, XAFS, UV–Vis and HR-TEM shows a uniform dispersion of highly dispersed CeOx within the mesoporous silica framework. The CO2 hydrogenation properties were investigated in a fixed-bed flow reactor and complemented by CO2-TPD, CO2-TPSR, in-situ FTIR, and D2 kinetic isotope experiments. The results show that highly dispersed CeOx exhibits excellent CO2 adsorption and dissociation abilities. The inverse kinetic isotope effect indicates that CO2 activation is the rate-determining step of the reaction. CO2 is strongly adsorbed on CeOx to form bidentate carbonate, which accelerates the generation of CO while avoiding the adsorption of CO2 on Ni nanoparticles.