Bandgap engineering of NiO, and enhanced photocatalytic performance by Ca doping

Wide bandgap NiO is vital for the photodegradation of organic molecules like dyes, bacteria, viruses, and for water decontamination. Calcium oxide is another efficient catalyst due to the presence of greater active sites. In this study, CaO molecules were incorporated into the NiO matrix by calcium doping. It was assumed that the incorporation of CaO would enhance the photocatalytic performance of NiO. Pure and calcium substituted NiO samples were prepared by simple co-precipitation method. The samples were characterized by X-ray diffractometer, SEM, UV–visible, and FTIR spectrometer. XRD profiles show the successful formation of NiO and Ca-doped NiO cubic nano crystallites. UV–visible spectroscopy revealed a shift in absorbance peaks toward longer wavelengths and decreased bandgap in Ca-doped samples. Photodegradation study revealed superior photocatalytic performance of doped samples under similar conditions. The improved photocatalytic performance of Ca-doped NiO is attributed to greater active sites and decreased bandgap due to the formation of new energy levels by the impurity addition. This study demonstrates that calcium doping in nickel oxide has enhanced the photodegradation efficiency from 45 % to 98.15 %.