An Artificial Z‑Scheme Constructed from Dye-Sensitized Metal Oxide Nanosheets for Visible Light-Driven Overall Water Splitting

Sensitization of a wide-gap oxide semiconductor with a visible-light-absorbing dye has been studied for decades as a means of producing H₂ from water. However, efficient overall water splitting using a dye-sensitized oxide photocatalyst has remained an unmet challenge. Here we demonstrate visible-light-driven overall water splitting into H₂ and O₂ using HCa₂Nb₃O₁₀ nanosheets sensitized by a Ru­(II) tris-diimine type photosensitizer, in combination with a WO₃-based water oxidation photocatalyst and a triiodide/iodide redox couple. With the use of Pt-intercalated HCa₂Nb₃O₁₀ nanosheets further modified with amorphous Al₂O₃ clusters as the H₂ evolution component, the dye-based turnover number and frequency for H₂ evolution reached 4580 and 1960 h^–1, respectively. The apparent quantum yield for overall water splitting using 420 nm light was 2.4%, by far the highest among dye-sensitized overall water splitting systems reported to date. The present work clearly shows that a carefully designed dye/oxide hybrid has great potential for photocatalytic H₂ production, and represents a significant leap forward in the development of solar-driven water splitting systems.