CuO Quantum Dots Decorated TiO₂ Nanocomposite Photocatalyst for Stable Hydrogen Generation

An efficient and stable CuO-TiO₂ nanocomposite photocatalyst was synthesized by using the simple molten-salt method. Characterization by HR-TEM confirmed the existence of both TiO₂ and CuO in the nanocomposite, revealing hexagonal TiO₂ nanoparticles (NPs) with average particles size of 23.8 nm. CuO QDs decorated on the TiO₂ surface were in the range of 2.2 to 4.6 nm. Photocatalytic experiments for hydrogen (H₂) production were carried out under an LED (λ = 365 nm) lamp and natural solar light. The effect of Cu-loading in CuO-TiO₂ NCs and synthesis time were studied. The optimized CuO-TiO₂ NCs abbreviated as CuT-4 and CuT-3 showed 27.7- and 9.0-fold superior rate of H₂ production compared to pristine TiO₂ NPs under LED and solar irradiation, respectively. At optimal conditions, CuO-TiO₂ NCs demonstrated good photostability for H₂ evolution during 75 h illumination under LED light. The experimental results confirmed the cocatalytic role of CuO for improved H₂ generation by a minimized recombination of excitons

CaFe2O4 sensitized hierarchical TiO2 photo composite for hydrogen production under solar light irradiation

Hierarchical spheres of self organized nanosheets of TiO2 are prepared by solvothermal method. The spheres comprising nanosheets are expected to exhibit high conducting properties. The present work is an attempt to explore the conducting properties of these spheres of TiO2 nanosheets that facilitate charge transfer and charge mobility. And at the same time to extend the absorption of TiO2 to visible light, it is combined with a low bandgap semiconductor CaFe2O4. In this perspective, CaFe2O4/TiO2 composite photocatalyst consisting of CaFe2O4 and TiO2 hierarchical spheres of nanosheets is prepared by solid state dispersion (SSD) method. The photocatalysts are characterized by thermo gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption desorption, photoluminescence (PL) and UV-Vis diffuse reflectance spectra (DRS). SEM and TEM images show TiO2 spheres and the mesoporous structure is substantiated by the N2 adsorption desorption studies. UV-Vis DRS of the composites show visible light absorption confirming the sensitization of TiO2 by CaFe2O4. XRD shows the crystallinity of the prepared composites is anatase and SEM confirms that the TiO2 spheres are intact at 400??C calcination temperature. However, deformation of spheres is seen at higher temperatures. Photocatalytic activity of the composites is studied using methanol water mixtures and optimum conditions for hydrogen production are established. By comparing the activity of CaFe2O4/TiO2 composite under visible and solar light irradiation, the possible charge transfer processes that are responsible for the synergistic activity are visualized. Based on the results, a mechanism highlighting the structure activity correlation has been proposed.close0

Bismuth oxide cocatalyst and copper oxide sensitizer in Cu2O/TiO2/Bi2O3 ternary photocatalyst for efficient hydrogen production under solar light irradiation

A novel Cu2O/TiO2/Bi2O3 ternary nanocomposite was prepared, in which copper oxide improves the visible light absorption of Ti0(2) and bismuth oxide improves electron-hole separation. The ternary composite exhibited extended absorption in the visible region, as determined by UV-Vis diffuse reflectance spectroscopy. Highresolution transmission electron microscopy images showed close contact among the individual semiconductor oxides in the ternary Cu2O/TiO2/Bi2O3 nanocomposite. Improved charge carrier separation and transport were observed in the Cu2O/TiO2/Bi2O3 ternary composite using electrochemical impedance spectroscopy and photocurrent analysis. TiO2 modified with bismuth and copper oxides showed exceptional photocatalytic activity for hydrogen production under natural solar light. With optimum bismuth and copper oxide loadings, the Cu2O/ TiO2/Bi2O3 ternary nanocomposite exhibited an H-2 production (3678 mu mol/h) 35 times higher than that of bare TiO2 (105 mu mol/h). The synergistic effect of improved visible absorption and minimal recombination was responsible for the enhanced performance of the as-synthesized ternary nanocomposite