Structural, optical and photocatalytic properties of silver-doped magnesia: computational and experimental study

Abstract In this work, the potential of silver-doped magnesia as a heterogeneous photocatalyst for the degradation of methylene blue using visible light as irradiation source was investigated. Effects of different parameters, such as initial dye concentration, dopant concentration, and catalyst amount were checked for optimum conditions. In addition, this study was designed to evaluate the effects of silver-doping on the structural and optical properties of magnesia by the application of various analytical techniques such as: scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) spectroscopy, powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and ultraviolet–visible spectroscopy (UV–Vis). Furthermore, density functional theory calculations were also performed to get an insight into the doping phenomena. From the calculations it was found that doping of silver greatly effects the structural and optical properties of magnesia, where band gap decreases and lattice constant, total stress, total force, and total energy of the system increases. By comparing the computational and experimental results, it was confirmed that the large ionic radius of silver prevents it from incorporation into the MgO matrix. Spin-polarized DFT calculations were also performed for Ag-adsorption on MgO (1 0 0) surface, which revealed that the corners are the most favorable sites for Ag-physisorption. The prepared photocatalysts showed satisfactory results and almost completely degraded methylene blue in the initial seven hrs. The results show that silver-supported magnesia photocatalyst has a great potential to be applied for removal of methylene blue from contaminated water.