An efficient and stable CuO-TiO 2 nanocomposite photocatalyst was synthesized by using the simple molten-salt method. Characterization by HR-TEM confirmed the existence of both TiO 2 and CuO in the nanocomposite, revealing hexagonal TiO 2 nanoparticles (NPs) with average particles size of 23.8 nm. CuO QDs decorated on the TiO 2 surface were in the range of 2.2 to 4.6 nm. Photocatalytic experiments for hydrogen (H 2 ) production were carried out under an LED (λ = 365 nm) lamp and natural solar light. The effect of Cu-loading in CuO-TiO 2 NCs and synthesis time were studied. The optimized CuO-TiO 2 NCs abbreviated as CuT-4 and CuT-3 showed 27.7-and 9.0-fold superior rate of H 2 production compared to pristine TiO 2 NPs under LED and solar irradiation, respectively. At optimal conditions, CuO-TiO 2 NCs demonstrated good photostability for H 2 evolution during 75 h illumination under LED light. The experimental results confirmed the cocatalytic role of CuO for improved H 2 generation by a minimized recombination of excitons.

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Crude glycerol (10% w/w) is produced as a substantial byproduct during the industrial production of biodiesel via transesterification processes. Catalytic hydrogen (H 2 ) generation by utilizing crude glycerol and solar light is considered as a promising avenue. The present work illustrates enhanced rates of H 2 generation and cocatalyst behavior of Ni(OH) 2 decorated on TiO 2 nanotubes dispersed in aqueous crude glycerol solution (industrial byproduct) under solar light irradiation. The catalyst characterization reveals that the TiO 2 nanotubes (TNT) are of anatase phase with length ranges from 100 to 300 nm and diameters from 4.9 to 9.8 nm. The Ni(OH) 2 quantum dots deposited on TNT have an average particle size of 8.4 nm. The presence of Ni(OH) 2 on TNT and oxidation states of Ti 4+ and Ni 2+ cations are confirmed by XPS analysis. The optimal loading of Ni (2.0 wt %) leads to a high rate of photocatalytic H 2 generation of 4719 μmol h −1 g cat −1 and it is ∼12-fold higher than pristine TNT. The solar light energy conversion efficiency of the optimized catalyst and cost benefit analysis by using crude glycerol are also evaluated. The high electronegativity of Ni(OH) 2 quantum dots present on the surface of TNT may facilitate effective shuttling of photoexcitons, thereby largely preventing electron−hole recombination in TiO 2 during photocatalysis.

In this work, a photochemical device that contains thioalkyl-substituted tetrathiafulvalene dyes and hierarchical porous TiO2 has been designed and successfully employed in visible light-driven hydrogen production. The design strategy boosts up the desirable photophysical properties of catalysts and is well supported by optical, electrochemical, and computational studies. The introduction of thioalkyl-substituted tetrathiafulvalene dyes as light-harvesting sensitizers onto the porous TiO2 triggers unprecedented high rate of hydrogen evolution. This study focuses on the role of thiafulvalene scaffold, which can promote ultrafast interfacial electron injection from excited-state dye into the hierarchical porous TiO2 conduction band. The purposeful construction of this integrated composite G3T3 (dye content 1.0 μmol in 10 mg Pt-TiO2 composite) significantly increases the hydrogen production rate of 24 560 μmol h–1 gcat –1 with high apparent quantum yield ∼41%. In the study, the absorption onset of both sensitizers extends up to 500 nm in solution and 600 nm on hierarchical porous TiO2. Density functional theory in the present study described that the highest occupied molecular orbital levels are delocalized on anthracene as well as on tetrathiafulvalene donor units and that lowest unoccupied molecular orbital covers the carboxylate anchoring group in both dyes. This study unveiled for the first time that a tetrathiafulvalene scaffold in porous TiO2 attributes to positive synergistic effects in hydrogen production.

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