Panchromatic Pt/TiO2-Based Photocatalysts Sensitized with Carboxylated Chlorin Dyads for Water Splitting Hydrogen Evolution

Abstract

Harvesting and converting solar energy into hydrogen production provides a new strategy for the global energy crisis. Since TiO2, the most widely used photocatalyst, absorbs light limited in ultraviolet region, extension of photo-response in visible to near-infrared region by dye-sensitization of TiO2 photocatalysts has attracted more and more attention in the field of artificial photosynthesis. In this work, three chlorophyll(Chl)-related sensitizers were designed to realize panchromatic light-absorption to simulate the charge separation process in natural photosynthetic reaction centers. The dyad sensitizers were synthesized by covalently-linking two different types of chromophore units derived from natural Chls-a/b, and their effects of Pt/TiO2-based photocatalysts for water splitting hydrogen evolution reaction (HER) were investigated. The Pt/TiO2 composite sensitized with Chl-a type dyad showed the best photocatalytic HER performance, and the H2 evolution of 5.4 mmol g-1h-1 was achieved. Electronic absorption, fluorescence emission, and time-resolved photoluminescence spectra as well as photocurrent responses and electrochemical impedance measurements were used to reveal the key factors of dyad sensitizers that influence the performances of Pt/TiO2 based photocatalysts. This work provides insights to explore new organic dye-sensitizers for improving the performance of TiO2-based photocatalysts.