Enhanced photocatalytic degradation of rhodamine B by surface modification of ZnO with copper (II) porphyrin under both UV–vis and visible light irradiation

Abstract

In this paper, a new organic–inorganic CuPp–ZnO photocatalyst was achieved by copper (II) 5-mono-[4-(2-ethyl-p-hydroxybenzoate)ethoxyl]-10,15,20-triphenylporphyrin (CuPp) impregnated onto the surface of ZnO with an effective mixing method. Then the CuPp–ZnO photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR) spectroscopy and photoluminescence spectra (PL). The results revealed that CuPp successfully impregnated onto the surface of ZnO and there existed an interaction between ZnO and CuPp. The photocatalytic activities of the CuPp–ZnO photocatalyst were evaluated in the photocatalytic degradation of rhodamine B (RhB) both under UV–vis and visible light (λ≥420nm) irradiation. It was found that the CuPp–ZnO photocatalyst showed much higher photodegradation efficiency than bare ZnO, which improved the separation of photogenerated electrons and holes. The active species during the photocatalytic reaction were detected by using different types of active species scavengers. Finally, the photocatalytic mechanisms both under UV–vis and visible light irradiation were proposed. In addition, the repetition test demonstrated that the CuPp–ZnO still maintained high photocatalytic activity over five recycles. Based on the present study, it could be considered as a promising photocatalyst for future applications.