Hybrid CuxO-TiO2 Nanopowders Prepared by Ball Milling for Solar Energy Conversion and Visible-Light-Induced Wastewater Treatment

Hybrid nanocomposites of Cu2O-(R)TiO2, CuO-(R)TiO2, and Cu3TiO4-(R)TiO2 (where R represents the rutile phase of TiO2) nanopowders (NPs) were produced via solid state reaction followed by 20 h of ball milling; their photocatalytic activities were evaluated for methylene blue (MB) degradation under visible light intensity (similar to 65 mW/cm(2)) and compared to Degussa P25 under both ultraviolet (UV) and visible light irradiations. The highest MB degradation rate under the visible light irradiation was observed to be 0.271 +/- 0.010 h(-1) for Cu2O-(R)TiO2 NPs, which was 2.5 times higher than that of P25, while under UV illumination both the Cu2O-(R)TiO2 and Cu3TiO4-(R)TiO2 NPs were slightly less active than that of the P25, and CuO-(R)TiO2 was the least active among all. The solar energy conversion performance of the CuxO-(R)TiO2 NPs was observed to be controlled by the applied potentials. The highest stable cathodic photocurrent density (6.3 mu A/cm(2)) was observed for Cu2O-(R)TiO2 NPs at a low negative bias voltage (-0.3 V vs Ag/AgCl, 3 M KCl) and under the solar simulator (AM 1.5G). This method to design multifunctional visible-light-active metal oxides is simple and scalable and has the potential to prepare other efficient photocatalysts for solar energy conversion.