Aiman Noman - Department of Environmental Science, Yuvaraja’s College, University of Mysore, Mysore ۵۷۰۰۰۵, Karnataka, India.
Mohammed A. Alghobar - Agricultural Research and Extension Authority, Ministry of Agriculture, Yemen.
Sidduraiah Suresha - Department of Environmental Science, Yuvaraja’s College, University of Mysore, Mysore ۵۷۰۰۰۵, Karnataka, India.

In this study, p-n junction photocatalyst CuO/CeO۲ZrO۲ with different concentrations of CuO was prepared by auto solution combustion method using glycine as fuel. This method is simple, fast and cost effective compared with other preparation methods. The photocatalyst was characterized by X-ray diffraction (XRD), energy-dispersive spectrometer (EDS), UV-vis DRS. The assembly of p-type CuO nanoparticles produces a large number of nano p–n junction heterostructures on the surface of the CeO۲ZrO۲ nanocrystals, where CuO and CeO۲ZrO۲ form p- and n-type semiconductors. The experimental results reveal that p–n junction CuO/CeO۲-ZrO۲ heterojunction nanostructures exhibit much higher visible-light photocatalytic activities than the n-CeO۲-ZrO۲ for the removal of dye from industerial waste water. The photocatalytic activity of the p-n CuO/CeO۲-ZrO۲ heterojunction photocatalyst was evaluated using the degradation of aqueous methylene blue solution (MB) under visible light irradiation(λ>۴۲۰ nm). The photo-degradation rate of this catalyzed is much faster than those occurring on n-type CeO۲ZrO۲. The sample with a p-n CuO/ CeO۲-ZrO۲ molar ratio of ۰.۰۲۱ presented the best photocatalytic activity, which was ۳۰% higher than that of n-type CeO۲ZrO۲. The heat treatment condition also influences the photocatalytic activity strongly, and the best preparation condition is about ۴۰۰ºC for ۴h.

p-n CuO/ CeO۲-ZrO۲ heterojunction, photocatalyst, wastwater, Combustion Method