Tuning the Properties of Benzothiadiazole Dyes for Efficient Visible Light-Driven Photocatalytic H2 Production under Different Conditions

Photocatalytic hydrogen production has recently emerged as a promising process for the long-term storage of solar energy. In this work, we studied the application to H2 generation of a series of heterogeneous photocatalysts obtained by sensitizing Pt/TiO2 nanoparticles with ten different D-pi-A organic dyes containing the benzo[c][1,2,5]thiadiazole (BTD) heterocyclic moiety. Starting from the known DSSC sensitizer RK-1, our approach involved the systematic and simultaneous alteration of several important structural features, such as steric bulk and hydrophobicity/hydrophilicity in different parts of the molecules, giving rise to a set of compounds with diverse physico-chemical properties. Visible light-driven H2 generation studies conducted with the dye-sensitized photocatalysts together with different sacrificial electron donors (SED) revealed that both their overall hydrogen production efficiency and their relative order of performances could be altered by the choice of SED and the corresponding reaction conditions. In particular, the best results were obtained with dyes having a strongly hydrophobic central core and a hydrophilic donor section in combination with ascorbic acid as the electron donor. In addition, the effect of changing the dye loading and extending the reaction time was examined, resulting in a stable three-component photocatalytic system displaying high activity up to 72 hours of experiment.