Dye-sensitized photocatalytic and photoelectrochemical hydrogen production through water splitting

Abstract: This review points out some of our recent advancements in dye-sensitized photocatalytic and photoelectrochemical hydrogen production. The dye sensitization of a semiconductor (SC) surface plays a central role. The dye has the task to improve the light harvesting of the system and guarantees a fast charge transfer to the SC, while avoiding charge recombination reactions that might reduce its efficiency. The introduction of different features and exploitation of molecular designs led to the development of twelve new dyes with a “push–pull” di-branched structure. The design of the molecular structure and geometry improves light harvesting, stability under long-term irradiation, and surface properties. The dyes have been investigated in a photocatalytic device, and then the most representative molecules have been studied also in photoelectrochemical cells (PEC), in the presence either of a sacrificial electron donor (SED), or of a water oxidation catalyst (WOC). The planar structure of the carbazole-based dye enhanced the photocatalytic hydrogen production activity almost tenfold compared to the phenothiazine derivative characterized by a butterfly-like structure; the latter was endowed with a better performance in the photoelectrochemical hydrogen production. Graphic abstract: [Figure not available: see fulltext.]