A Cu-Au bimetallic co-catalysis for the improved photocatalytic activity of TiO2 under visible light radiation

This study represents the co-catalytic activity of mono/bimetallic loaded titanium dioxide (TiO2) nanocomposite of copper (Cu) & gold (Au) for the photo-reduction of aromatic nitro compounds and the photo-oxidation of salicylic acid. It was observed that the average hydrodynamic size of Cu (similar to 21 nm) and Au (similar to 25 nm) increased after the formation of core-shell structure (similar to 36 nm and similar to 38 nm for Cu@Au and Au@Cu respectively). The morphological studies revealed the uniform coating of Cu-shell of thickness similar to 2.1 nm over Au core. Moreover, in optical analysis a considerable blue-shift in the absorption band of Cu@Au (600 nm-559 nm) and a red-shift in Au@Cu (528-580 nm) with significant change in color were observed with increasing the amount of Au and Cu, respectively. Under visible light irradiation these bimetallic/TiO2 nanocomposite showed higher activity for the reduction of 3-nitroacetophenone and 1-chloro-3-nitrobenzene and oxidation of salicylic acid comparative to their monometallic counter parts with a higher rate constant k = 0.97 x 10(-2) min(-1) (Au@Cu/TiO2), k = 0.65 x 10(-2) min(-1) (Cu@Au/TiO2) relative to monometallic (k = 034 x 10(-2) min(-1) (Cu/TiO2) and k = 0.29 x 10(-2) min(-1))) for the oxidation of salicylic acid. The higher activity of bimetallic/TiO2 nanocomposite is ascribed to the decrease in work function (4.2 for Au@Cu/TiO2 & 4.6 for Cu@Au/TiO2) resulting in the proficient transfer of electrons at bimetallic-TiO2 interface. (C) 2017 Elsevier Ltd. All rights reserved.