Theoretical investigation of carbon dioxide adsorption on MgH 2 with a cobalt catalyst

Abstract

CO 2 adsorption mechanisms were investigated on an MgH 2 substrate using CO 2 activation. Cobalt catalyst enhanced CO 2 chemical adsorption on top of Co SAC, while non-catalysed MgH 2 induced CO 2 physisorption on top of MgH 2 interatomic cavities. This work presents a theoretical investigation of carbon dioxide (CO 2 ) adsorption on MgH 2 and its reaction (chemisorption) with cobalt doped MgH 2 . The focus of this study is the properties and mechanisms involved in CO 2 adsorption on clean MgH 2 surfaces and the role of Co in enhancing the adsorption process. Density functional theory (DFT) calculations were performed to examine different CO 2 adsorption sites on the MgH 2 surface along with the adsorption distances, binding energies, and geometric parameters. The results indicate that physical adsorption of CO 2 occurs on MgH 2 with similar adsorption energies at different adsorption sites. The coverage effect of CO 2 molecules on MgH 2 was also investigated, revealing an increased affinity of CO 2 with higher surface coverage. However, excessive coverage led to a decrease in adsorption efficiency due to competing surface adsorption and intermolecular interactions. The orientation of adsorbed CO 2 molecules shifted from parallel to quasi-perpendicular arrangements upon adsorption, with notable deformations observed at higher coverage, which gives a hint of CO 2 activation. Furthermore, the study explores the CO 2 adsorption capacity of MgH 2 in comparison to other materials reported in the literature, showcasing its medium to strong affinity for CO 2 . Additionally, the effectiveness of a single Co atom and Co clusters as catalysts for CO 2 adsorption on MgH 2 was examined. Overall, this theoretical investigation provides insights into the CO 2 adsorption properties of MgH 2 and highlights the potential of Co catalysts to enhance the efficiency of the methanation process.