Improved photocatalytic activity and mechanism of Cu2O/N–TiO2 prepared by a two-step method

Abstract

Cu₂O/N–TiO₂ was achieved through a two-step route by deposition of CuO on Degussa P25 TiO₂ using a wet impregnation method and then treatment with N₂/Ar plasma. The morphology, composition, and structure of the prepared catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). XRD spectra indicated that neither the low-content copper oxides nor the plasma treatment changed the crystalline phase of TiO₂. XPS results indicated the transformation of Cu species from CuO to Cu₂O and the doping of N after plasma treatment. EPR spectra confirmed the formation of Ti³⁺ that was also induced by plasma treatment. TEM analysis revealed that the well crystallized Cu₂O nanoparticles, existed with sizes of ∼3 nm, dispersed uniformly on the surface of TiO₂. As for the optical absorption curves obtained by UV-vis absorption spectroscopy, an extended absorption edge of Cu₂O/N–TiO₂ was confirmed compared with that of TiO₂ and CuO/TiO₂. In addition, the photodegradation efficiency of methyl orange (MO) solutions over Cu₂O/N–TiO₂ were markedly enhanced under both the visible and full-spectrum light irradiation in comparison with TiO₂ and CuO/TiO₂. The mechanism of photocatalytic reaction over Cu₂O/N–TiO₂ corresponding to UV and visible light irradiation was discussed.