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.

Photocatalytic H2 Production from Water by Metal‐free Dye‐sensitized TiO2 Semiconductors: The Role and Development Process of Organic Sensitizers

“…The fitted τ1 lifetimes of G1 and G3 were almost the same (0.11 and 0.12 ns), however the τ2 lifetime of G3 (1.75 ns) was longer than that of G1 (1.24 ns), which corresponded to the lower charge recombination as well as higher photo activity in H 2 evolution. The optimized DSP of G3 achieved a remarkable H 2 yield of 123 mmol g −1 under irradiation (>500 nm) after 5 h, and a high AQY of 40.87 % was obtained under 450 nm monochrome light [72] …”

“…The optimized DSP of G3 achieved a remarkable H 2 yield of 123 mmol g À 1 under irradiation (> 500 nm) after 5 h, and a high AQY of 40.87 % was obtained under 450 nm monochrome light. [72] Besides being as π-spacer mentioned above, DPP group could also be involved as donor moiety due to its well-established synthesis, adjustable photophysical properties and high performances as already reported in optoelectronic devices such as organic transistors and organic and hybrid solar cells. [73] Julien Warnan et al reported the first example of a series of DPP dyes with a terminal phosphonic acid group, bearing different side-chains and electronically active substituents (Figure 35 and Table 1, No.…”

Consecutive Charging of a Perylene Bisimide Dye by Multistep Low‐Energy Solar‐Light‐Induced Electron Transfer Towards H2 Evolution

“…Splitting water into hydrogen and oxygen by photocatalysts is recognized as one of the promising strategies to utilize and store the inexhaustible solar energy . Dye sensitized titanium dioxide (TiO 2 ) and wide band gap metal oxides are widely used as photocatalysts because of the abundance of both organic dyes and metal oxides and the tunable energy level alignments between them, which enables the combination of efficient solar energy harvesting and charge separation capability . The minimum theoretical energy threshold for water splitting is 1.23 eV, but the energy of the photons used for this process is typically larger than 2.0 eV as a result of a number of energy‐loss processes including the reorganization of the excited state of the photocatalyst system, overpotential of half reactions, and the energy lost in the charge‐transfer (redox) processes.…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…Different types of photoactive compounds can be included in the design of a dye with specific structure: some D-A-π-A perylene dyes, featuring cyanoacrylic acid and dicyanomethylene rhodamine as the acceptor/anchoring group, combined with a N-annulated perylene donor and a quinoxaline auxiliary acceptor [63]; two triphenylamine-benzimidazole-based dyes bound on TiO 2 , with Cu 2 WS 4 nanocubes as an alternative water splitting co-catalyst to Pt [64]; a particular composite dye, consisting of π-conjugated indoline-rhodanine with a chlorophyll derivative, which induced panchromatic absorption in the visible range, efficient electron transfer, and prolonged stability [65]; a series of dyes with triphenylamine donor, vinyltiophene bridge, and a cationic pyridinium acceptor (cationic D-π-A photosensitizers) [66]. A superior H 2 evolution rate was recently reached with a thioalkyl-substituted tetrathiafulvalene dye on mesoporous TiO 2 [67].…”