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

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 N-2/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 similar to 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.