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 H 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 H and O using HCaNbO nanosheets sensitized by a Ru(II) tris-diimine type photosensitizer, in combination with a WO-based water oxidation photocatalyst and a triiodide/iodide redox couple. With the use of Pt-intercalated HCaNbO nanosheets further modified with amorphous AlO clusters as the H evolution component, the dye-based turnover number and frequency for H evolution reached 4580 and 1960 h, 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 H production, and represents a significant leap forward in the development of solar-driven water splitting systems.