In situ loading of ultra-small Cu2O particles on TiO2 nanosheets to enhance the visible-light photoactivity

In this work, ultra-small Cu2O nanoparticles have been loaded on TiO2 nanosheets with {001} facets exposed through a one-pot hydrothermal reaction. These Cu2O nanoparticles are well-dispersed on TiO2 nanosheets with narrow size distributions and controllable sizes from 1.5 to 3.0 nm. Through XRD, TEM, N-2 absorption-desorption isotherms and UV-vis diffuse reflectance spectra, the Cu2O/TiO2 nanosheets show similar phase structures, morphologies, pore structures as compared to pure TiO2 nanosheets. Due to the loading of ultra-small Cu2O nanoparticles, heterojunctions are formed between Cu2O and TiO2, which favors the efficient separation of photo-generated electrons and holes. Caused by the electron transfer from Cu2O to TiO2, Cu2O/TiO2 nanosheets show excellent visible-light activity, about 3 times that of N-doped TiO2 nanosheets with {001} facets exposed. Furthermore, charge transfer rate across the interface of Cu2O and TiO2 shows great dependence on the size of Cu2O particles. The charge transfer across the interface may be more efficient between TiO2 nanosheets and smaller Cu2O nanoparticles. Therefore, the Ti : Cu 30 : 1(atomic ratio) sample shows the best activity due to its balance in light harvest and electron transfer rate in the degradation of phenol under visible light.