Diameter-dependent photocatalytic performance of niobium pentoxide nanowires.

Thermal reactions of a niobium oxo-oxalate complex, (NH4)3[NbO(Ox)3]·H2O, with ternary amines having more than two methylene chain units as structure directing solvents led to self-assemblies suitable for one dimensional growth to afford amorphous niobium oxide nanowires whose diameters depended on methylene chain lengths in the amines. These nanowires were crystallized at 773 K to obtain the TT phase of Nb2O5 whilst maintaining the same structure as before calcination. There was almost no difference in crystallinities, BET surface areas, and growth directions among the Nb2O5 nanowires. PtCl6(2-) was reduced by photogenerated electrons in the conduction band of the Nb2O5 nanowires following UV light irradiation (λ > 300 nm) in the presence of an electron donor. Metallic Pt nanoparticles were selectively deposited on a short axis plane of the nanowires prepared with tridodecylamine, whereas the others had the Pt nanoparticles throughout the surfaces. This indicated that photogenerated electrons moved along the nanowire growth direction associated with transfer of holes to the nanowire sidewall. The anisotropic carrier transport afforded the highest activity for photocatalytic H2 evolution reactions under UV light irradiation (λ > 300 nm).