Development of Triphenylamine Derived Photosensitizers for Efficient Hydrogen Evolution from Water

A series of new (donor)₂-donor-π-acceptor (D₂-D-π-A) and (acceptor)₂-donor-π-acceptor (A₂-D-π-A) organic photosensitizers based on the framework of (Z)-2-cyano-3-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)acrylic acid have been synthesized and characterized. By incorporating groups with different electron-donating or withdrawing abilities, such as dibenzothiophene (DBT), dibenzofuran (DBF), and triazine (TA), into the triphenylamine segment, their photophysical properties have been regulated. Theoretical calculations were used to explore how various donor-acceptor combinations influence their hydrogen production performance. Notably, DBF-CN achieved the highest turnover number (TON) of 10,202 and an initial turnover frequency (TOF_i) of 151.6 h^-1 under green light irradiation, with an initial activity (Activity_i) of 113,532 μmol g^-1 h^-1 and an apparent quantum yield (AQY_i) of 0.76 %. This dye-sensitized-TiO₂-Pt system is recognized as one of the most efficient and durable systems for photocatalytic hydrogen production under green light irradiation, as described in the literature, when compared using TOF and TON values. Experimental results indicate that the D₂-D-π-A system significantly enhances photocatalytic hydrogen evolution (PHE) performance more effectively than the A₂-D-π-A system, while also maintaining stability under prolonged light exposure.