Highly stable M/NiO-MgO (M = Co, Cu and Fe) catalysts towards CO2 methanation

NiO-MgO nanocomposites are synthesized using solution combustion, sonochemical, and co-precipitation synthesis to understand the catalytic activity of CO2 methanation. Excellent particle size distribution was noticed with the sonochemical routed synthesis method, and the CO2 conversions are found to be better with the same synthesis protocol. Surface modifications in NiO-MgO composite were incorporated by doping M (M = Co, Fe, and Cu). The active catalysts are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to understand physical, structural properties and surface morphology of the nanocomposites. All catalysts showed excellent catalytic activity for the conversion of CO2 to methane and selectivity towards methane to be higher than 85%. However, 2%Co/NiO-MgO showed the lowest activation energy of about 43 +/- 2 kJ mol(-1) among other synthesized catalysts. The mechanism of CO2 methanation was investigated with the inputs from temperature programming reduction with H-2 (H-2-TPR), and temperature programming desorption with CO2 (CO2-TPD) studies. Detailed reaction mechanism and kinetics are investigated for all doped catalysts. M/NiO-MgO offered excellent stability up to 50 h reaction time with high CO2 conversions and CH4 selectivities. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.