Cr-doped, ZrO2 modified TiO2/ZnO, visible light, hydrogen
Visible light active nanocomposites were synthesized by the sol-gel method using non-ionic surfactant as a template. Cr-doped ZrO2-modified coupled ZnO/TiO2 composite was thoroughly characterized for surface area, crystal phase, microstructure, elemental identification and band gap measurement by nitrogen isotherm, powder X-ray diffraction, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy and UV-Vis diffuse reflectance spectroscopy. The results of diffuse reflectance spectra revealed that the absorption in the visible region is significantly improved for Cr-doped composites. The calculated optical band gap is reduced from 2.96 eV to ~1.7 eV. The BET specific surface area (SSA) of Cr-doped nanocomposites has shown higher surface area than that of ZrO2-modified coupled ZnO/TiO2 nanocomposite. The BET SSA was found to increase with increase in the amount of chromium used to prepare a nanocomposite. The performance of these photoactive nanocomposites was investigated towards H2 generation from aqueous methanol solution under AM1.5 simulated light illumination and results obtained were compared with the activity of TiO2, coupled ZnO-TiO2 composite and ZrO2-modified coupled ZnO/TiO2 composite.