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

Hybrid materials consisting of a ruthenium(II) polypyridyl complex and a Dion–Jacobson type perovskite oxide nanosheet were studied as photocatalysts for dye-sensitized H2 evolution under visible light with respect to the energy structure of the hybrids. Three Ru(II) complexes, RuII{(4,4′-X2-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 H2 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...