Interfacial charge transfer dynamics in TiO 2 -sensitizer-Ru 4 POM photocatalytic systems for water oxidation

Abstract

Efficient solar-driven catalytic water oxidation is one of the main challenges in solar-to-fuel conversion. In this proceeding, we investigate three approaches for constructing electron acceptor -sensitizer - catalysts systems for photocatalytic water oxidation and our current understanding of the relevant fundamental processes involved. We demonstrated that an all-inorganic molecular water oxidation catalyst (WOC), [{Ru₄O₄(OH)₂(H2O)₄}(γ-SiW10O36)2]10- (or Ru₄POM), catalyzed a homogenous O₂ evolution system with 27% quantum efficiency in homogeneous solution in the presence of sensitizer (Ru(bpy)3) and sacrificial electron donor.¹ This suggests the feasibility of a heterogeneous photoelectrochemical system in which the photoanode integrates all three components: electron acceptor, photosensitizer, and WOC. We prepare a photocatalytic electrode based on Ru₄POM and a dye-sensitized nanoporous TiO₂ film for efficient light-harvesting and charge separation. Ultrafast spectroscopic studies of this triadic nanocomposite indicate efficient charge separation from the excited sensitizer to TiO₂ and efficient regeneration of the ground state of the dye. The latter can be attributed to Ru₄POM oxidation by the photogenerated dye cation and has a yield of > 80% within 1 ns.