Towards Sustainable H₂ Production: Rational Design of Hydrophobic Triphenylamine‐based Dyes for Sensitized Ethanol Photoreforming

Abstract

Donor-acceptor dyes are a well-established class of photosensitizers, used to enhance visible-light harvesting in solar cells and in direct photocatalytic reactions, such as H production by photoreforming of sacrificial electron donors (SEDs). Amines-typically triethanolamine (TEOA)-are commonly employed as SEDs in such reactions. Dye-sensitized photoreforming of more sustainable, biomass-derived alcohols, on the other hand, was only recently reported by using methanol as the electron donor. In this work, several rationally designed donor-acceptor dyes were used as sensitizers in H photocatalytic production, comparing the efficiency of TEOA and EtOH as SEDs. In particular, the effect of hydrophobic chains in the spacer and/or the donor unit of the dyes was systematically studied. The H production rates were higher when TEOA was used as SED, whereas the activity trends depended on the SED used. The best performance was obtained with TEOA by using a sensitizer with just one bulky hydrophobic moiety, propylenedioxythiophene, placed on the spacer unit. In the case of EtOH, the best-performing sensitizers were the ones featuring a thiazolo[5,4-d]thiazole internal unit, needed for enhancing light harvesting, and carrying alkyl chains on both the donor part and the spacer unit. The results are discussed in terms of reaction mechanism, interaction with the SED, and structural/electrochemical properties of the sensitizers.

Thiazole- and Thiadiazole-Based Metal–Organic Frameworks and Coordination Polymers for Luminescent Applications

“…They have been exploited for the preparation of synthetic fungicides like thiabendazole, anti-inflammatory drugs like Meloxicam or in the fabrication of OLEDs and semiconductors [51,52]. More recently, their application as fully organic sensitizers in solar cells (DSSC) for energy applications has also started to appear in the literature [53,54]. The preparation of thiazole-based MOFs/CPs (from ligand design to the polymer construction) is one of our main research activities [55][56][57][58][59].…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…All the following cases applied the sensitized photocatalysts for H 2 generation. For instance, in alkoxyphenyl-substituted carbazole dyes [54] and thiophenothiazine dyes [55], the longest alkyl chain gave the best H 2 production rates, thanks to the higher hydrophobicity, extending the charge separation lifetime; in triphenylamine-based dyes, bulkier substituents and additional phenyl donating groups [56] or a thiazolothiazole unit [57] gave higher stability and yields. Phenothiazine-based dyes, featuring thiophene-based spacers and different anchoring groups, have been extensively studied [19], determining an improvement of visible light H 2 generation of Pt/TiO 2 by the effect of the spacer structure [58] and the insertion of a peripheral glucose unit as co-adsorbent ( Figure 5) [59].…”

Combined LCA and Green Metrics Approach for the Sustainability Assessment of an Organic Dye Synthesis on Lab Scale

“…In the last years, TTZ5 has found application as a photosensitizer in the photocatalytic hydrogen production (Dessì et al, 2018) and in transparent thin-layer DSSCs (Dessì et al, 2014), which are very attractive for the production of colored, transparent modules to be applied in building-integrated photovoltaics. However, fulfilling this aim would require the preparation of large-scale panels, in turn demanding the development of a reliable and sustainable gram-scale preparation of the dye.…”

“…In this work, a mass-based green metrics and LCA combined approach is applied to obtain a gate-to-gate assessment on two new alternative synthetic protocols, specifically designed to scale-up the production of the organic dye TTZ5 (Figure 1), and compare their environmental performances with those of its original preparation (Dessì et al, 2014). Compound TTZ5, bearing a thiazolo[5,4-d]thiazole (TzTz) ring as its central unit, has been successfully employed as a sensitizer for the preparation of photocatalysts for hydrogen production (Dessì et al, 2018) and the manufacturing of dye sensitized solar cells (DSSCs) (Dessì et al, 2014(Dessì et al, , 2015. This innovative photovoltaic technology dates back to 1991 and was proposed as a more versatile and cheaper alternative to silicon based photovoltaic (PV) devices.…”