Unraveling the CO2 methanation and capture ability of NiO@metal oxides†
Abstract
The present study reports the development of different core–shell nanoparticles using Ni/NiO as the core and other active metal oxides such as SiO2, Co3O4, CeO2 and ZrO2 as shells for CO2 methanation. Among all the studied core–shell materials, NiO@SiO2 and NiO@CeO2 showed the highest catalytic activity of >62% for CO2 conversion and >99% selectivity towards CH4 with a high GHSV of 47 760 h−1 at 325 °C. The catalysts were thoroughly tested under lean and realistic feed conditions. XRD revealed the presence of NiO as the dominant core. All these catalysts were further subjected to characterization techniques such as SEM, TEM, XPS, N2 adsorption–desorption, H2-TPR, H2 pulse, and CO2-TPD-MS to understand their morphology, ionic nature, physical properties, reduction nature, active site dispersion, adsorption of CO2 and desorption of surface intermediates. Investigation into the formation and consumption of various intermediates via DFT studies revealed that the CO2 methanation reaction proceeds via a combination of the CO and formate pathways. These findings correlate with in situ FTIR studies, unveiling structure–property relations and methanation mechanisms. At 25 °C, NiO@SiO2 exhibited a superior CO2 capture performance of 301.96 mg of CO2 per g at 50 bar, while NiO@Co3O4 adsorbed 90.40 mg of CO2 per 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 CO2 capture and hydrogenation abilities towards methane formation.