Tetrathiafulvalene Scaffold-Based Sensitizer on Hierarchical Porous TiO₂: Efficient Light-Harvesting Material for Hydrogen Production

Abstract

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.