Photocatalysis of rhodamine B and methyl orange degradation under solar light on ZnO and Cu2O thin films

Abstract

We report the photocatalytic properties of ZnO and Cu2O thin films deposited on glass substrates at room temperature by DC sputtering and pulsed laser deposition. The photoactivity of the films was investigated through the degradation of rhodamine B (RhB) and methyl orange (MO) under solar light. In order to select the most suitable film of ZnO for the of RhB and MO degradation, the relationship between the characteristics (e.g. energy levels and defects concentration) of ZnO films and their effectiveness in the photocatalytic yield of RhB and MO been studied, where several films were deposited by using different oxygen partial pressures (PO2: 0.05–1.3 mbar), while Cu2O films were grown under a pressure of 0.01 mbar. The XRD patterns show that all ZnO films have (002) preferential orientation, and crystallite size increases from 73 to 122 nm raising PO2. The gap Eg of ZnO (3.26 and 4.15 eV) depends on PO2, and the films present photoluminescence emission in the UV–Vis-near IR region. On the basis of structural, optical and electrical characterizations of both films, a comparative study was carried out on the dyes degradation. Cu2O films exhibit a high photoactivity with MO (81.69%) under solar light (6 h), whilst for RhB the best elimination rate (60.85%) was achieved with ZnO films deposited at 0.1 mbar, which were also the ones exhibiting the highest PL peak intensity at the characteristic absorption wavelength of RhB (553 nm).