Kinetic Analysis of TiO2-based Photocatalysts Sensitized with Chlorophyll-Derived Dimers for Light-Driven Hydrogen Evolution

This study focuses on the kinetic analysis of chlorophyll-based dimer photosensitizers adsorbed on Pt/TiO2 photocatalyst for light-driven hydrogen evolution. To elucidate the detailed mechanism, four photosensitizers, a carboxylated chlorin (Chl) and its dimer derivatives connecting an accessory pigment of chlorin (Chl-PPa), porphyrin (Chl-Por), and bacteriochlorin (Chl-BPPa) were synthesized and their kinetic processes in photocatalytic hydrogen evolution were investigated. The results indicate that Chl-PPa possesses the highest ability to produce photogenerated carriers, with an appropriate excited state lifetime, lowest propensity for charge recombination, and longest charge transfer lifetime. These favorable characteristics contribute to its exceptional photocatalytic activity compared with other photosensitizers. Specifically, the Chl-PPa-sensitized Pt/TiO2 photocatalyst exhibits a remarkable hydrogen generation rate of 5.36 mmol/g/h. Moreover, these photosensitizers demonstrate excellent stability and multiple-experimental consistency. This study provides significant insights into the development of dyad photosensitizers and highlights their practical significance in the field of photocatalysis. By harnessing chlorophyll, we have successfully harnessed efficient and controlled hydrogen fuel generation through photocatalytic water splitting, thus paving the way for future advancements in clean and sustainable energy production.