Niobium Oxide Nanoscrolls as Building Blocks for Dye-Sensitized Hydrogen Production from Water under Visible Light Irradiation

Potassium hexaniobate nanoscrolls (NS-K4Nb6O17) formed by exfoliation of lamellar K4Nb6O17 were studied as building blocks for visible-light-driven H2 production (λ > 420 nm) from water using tris(2,2′bipyridyl)ruthenium(II) chloride (Ru(bpy)3) as a sensitizer and ethylenediaminetetraacetic acid (EDTA) as an electron donor. The surface of NS-K4Nb6O17 is negatively charged at pH 3-11, enabling cationic Ru(bpy)3 molecules to be efficiently adsorbed onto the surface, allowing for rapid excited-state electron and subsequent H2 evolution without any chemical bond linkage between the sensitizer and the oxide surface. The rate of visible light H2 production in the nanoscroll-based system is 10 times higher than that of similarly sensitized K4Nb6O17. The difference can be primarily attributed to the strong adsorption of Ru(bpy)3 in the case of the nanoscrolls. The maximum photocatalytic reactivity is found over a narrow range of pH and Pt-loading. This study highlights the utility of single-crystalline oxide nanosheets as components of photosystems for visible-light-driven H2 production from water.