Unraveling the CO2 methanation and capture ability of NiO@metal oxides

Abstract

Present study follows the development of different core-shell nanoparticles by keeping Ni/NiO as core and with other active materials such as SiO2, Co3O4, CeO2 and ZrO2 as shells for CO2 methanation. Out of all, both NiO@SiO2 and NiO@CeO2 showed highest catalytic activity of >62% of CO2 conversion and >99% selectivity towards CH4 with high GHSV of 47760 h-1 at 325ºC. The catalytic activity studies are presented using both lean and realistic feed conditions. XRD revealed the presence of NiO as dominant core. All these catalysts are further subjected to other characterization techniques such as SEM, TEM, XPS, BET, H2-TPR, H2 pulse, CO2-TPD-MS to understand the morphology, ionic nature, physical properties, reduction nature, active sites dispersion, finally adsorption of CO2 and desorption of surface intermediates. The investigation into the formation and consumption of various intermediates revealed that the CO2 methanation reaction in DFT studies proceeds via a combination of the CO and formate pathways. These findings are correlated with in situ FTIR studies by unveiling the structure-property relations and methanation mechanisms. At 25°C, NiO@SiO2 exhibited a superior CO2 capture of 301.96 mg of CO2/g at 50 bar, while NiO@Co3O4 adsorbed 90.40 mg of CO2/g at 1 bar. Interestingly, H2 adsorption was nearly uniform across all these materials even at 50 bar and 25°C. The core-shell materials show both capture and CO2 hydrogenation ability towards methane formation.