Mechanism of CO2 adsorption on point-defective MgO surfaces: First-principles study

Abstract

The mechanism of CO2 adsorption on two active MgO sites, formed after Mg-Al-CO3 layered double hydroxide (LDH) was calcined to form layered double oxide (LDO), was investigated by applying the first-principles calculations based on density functional theory (DFT). The results indicate that Al doping and surface vacancy activate the change of MgO (100) surface and the CO2 adsorption from initial physisorption to chemisorption compared to the pure MgO (100) surface. The charge density difference and partial density of states calculations suggest that Al doping leads to orbital hybridization between the O atom in CO2 and the surface Mg atom, forming a new MgO chemical bond, while vacancy leads to orbital hybridization between C and O atoms in CO2 and surface O and Mg atoms, respectively, forming new CO and MgO chemical bonds. In addition, crystal orbital Hamilton population (COHP) calculations show that the MgO bond formed by vacancy is stronger than the MgO bond formed by Al doping. The work provides us with more insight into finding more efficient CO2 capture agents to reduce greenhouse gas emissions.