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)32+) 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)32+ 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)32+ 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.