Hybrids of a Ruthenium(II) Polypyridyl Complex and a Metal Oxide Nanosheet for Dye-Sensitized Hydrogen Evolution with Visible Light: Effects of the Energy Structure on Photocatalytic Activity

摘要

Hybrid materials consisting of a ruthenium(II) polypyridyl complex and a Dion-Jacobson type perovskite oxide nanosheet were studied as photocatalysts for dye-sensitized H-2 evolution under visible light with respect to the energy structure of the hybrids. Three Ru(II) complexes, Ru-II{(4,4'-X-2-bpy)2(4,4'-(CH2PO3H2)(2)-bpy)} (X = H, CH3, CF3; bpy = 2,2'-bipyridine), were used as redox photosensitizers. HCa2-xSrxNb3O10 (0 = x = 2) and HCa2Nb3-yTayO10 (0 = y = 1.5) nanosheet aggregates, having a tunable conduction band potential (ECB), were employed as the building block. Nanosheets that possess more negative ECB value were found to be preferable for the dye-sensitized H-2 evolution, unless electron injection from the excited-state sensitizer to the conduction band of a nanosheet is hindered. Among the combinations tested, the highest activity was obtained when an HCa2Nb3O10 nanosheet was sensitized by RuII{(4,4'-(CH3)(2)-bpy)(2)(4,4'-(CH2PO3H2)(2)-bpy)}, exhibiting a maximum apparent quantum yield of ca. 10% at 460 nm and a turnover number of ca. 3800 (for 20 h). This study highlighted that it is possible to maximize the performance of dye-sensitized H-2 evolution on a sensitizer/semiconductor hybrid by refining the ECB value of a semiconductor and the oxidation potential of the excited state of a photosensitizer.