Evaluating the CO₂ capture potential of MgO sheets: a DFT study on the effects of vacancy and Ni doping for assessing...

Investigations on two-dimensional materials for efficient carbon dioxide (CO₂) capture and storage have recently attracted much attention, especially in the global industrial sector. In this work, the CO₂ uptake by three configurations of two-dimensional magnesium oxide was investigated using density functional theory. CO₂ capture analysis was performed considering the geometrical, thermophysical, vibrational, electronic and optical properties. Results indicated that CO₂ adsorption by magnesium oxide (MgO) sheets is a spontaneous process accompanied by a decrease in Gibbs free energy. Moreover, the CO₂ molecular entropy and enthalpy of the CO₂ adsorbed sheet were decreased, indicating that the entire process was enthalpy-driven. Among the pristine, vacant and nickel-doped (Ni-doped) MgO sheets, the Ni-doped system was found to have the highest values of Gibbs free energy, enthalpy and entropy in the order of -51.366 kJ mol^-1-K, -65.105 kJ mol^-1 and 127.606 J mol^-1, respectively. It was also found to adsorb CO₂ in the ultraviolet and visible (UV-Vis) regions within the range of 100-850 nm. Electronic interactions demonstrated that metallicity was significantly induced on the MgO sheet Ni impurity states, which enhanced the adsorption ability. Notably, hybrid orbitals between p and p revealed strong physisorption, as confirmed by the partial density of states (PDOS). The findings of this research promote CO₂ capture sustainability by encouraging future experimentalists to use two-dimensional MgO as a better surface for CO₂ capture.