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

Investigations on two-dimensional materials for efficient carbon dioxide (CO) capture and storage have recently attracted much attention, especially in the global industrial sector. In this work, the CO uptake by three configurations of two-dimensional magnesium oxide was investigated using density functional theory. CO capture analysis was performed considering the geometrical, thermophysical, vibrational, electronic and optical properties. Results indicated that CO adsorption by magnesium oxide (MgO) sheets is a spontaneous process accompanied by a decrease in Gibbs free energy. Moreover, the CO molecular entropy and enthalpy of the CO 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, -65.105 kJ mol and 127.606 J mol, respectively. It was also found to adsorb CO 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 CO capture sustainability by encouraging future experimentalists to use two-dimensional MgO as a better surface for CO capture.