Photocatalytic Degradation of Acid Orange 7 by NiO-TiO2/TiO2 Bilayer Film Photo-Chargeable Catalysts

Photocatalysis as an eco-friendly technology has the potential to achieve the Sustainable Development Goals (SDGs). However, an improvement of conventional photocatalysts is necessary to overcome their limitations such as slow kinetics, wavelength for excitation, and environmental restrictions. In particular, the development of a photocatalyst that can operate even in the absence of light is constantly conducted, and a photo-chargeable photocatalyst could be one of the answers. In this paper, a heterojunction composed of TiO2 and NiO-TiO2 bilayer film photocatalyst (BLF) was prepared. The effect of the synthesis conditions of the NiO-TiO2 layer on the photocatalytic properties was investigated. Photocatalytic degradation measurements were conducted with an acid orange 7 (AO7) solution under light and dark conditions. The highest degradation BLF was synthesized at a NiO loading of 52% and calcination temperature of 300 °C. The prepared sample showed about five-fold greater photocatalytic activity of 48% in AO7 degradation after 8 h compared to an ordinary TiO2 film (9%) under light conditions. Moreover, under dark conditions it exhibited 13.6% degradation, while the naked layers of TiO2 and NiO-TiO2 showed no degradation. The proposed mechanism suggested that photocatalysis in the dark was possible due to the stabilization of photogenerated holes by anionic intercalation during illumination.