Vertically aligned nanorod-like rutile TiO2 single crystal nanowire bundles with superior electron transport and photoelectrocatalytic properties

In this work, vertically aligned nanorod-like rutile TiO2 single crystal nanowire bundles were directly grown onto FTO conducting substrates via a facile, one-pot hydrothermal method. The fabricated nanorod-like rutile TiO2 single crystal nanowire bundles display a diameter range of 150-200 nm and a mean length of 0.9 mu m. The nanorod-like bundles assemble by individual single crystal nanowires of 5-7 nm in diameter. The photoanode made of vertically aligned nanorod-like rutile TiO2 single crystal nanowire bundles shows excellent photoelectrocatalytic activity towards water oxidation, which is almost 3 times higher than that of the photoanode made of vertically aligned anatase TiO2 nanotube film of similar thickness. The high photoelectrocatalytic activity of the photoanode made of the nanorod-like rutile TiO2 single crystal nanowire bundles is mainly due to the superior photoelectron transfer property, which has been manifested by the inherent resistance (R-0) of the rutile TiO2 film via a simple photoelectrochemical method. Using this approach, the calculated R-0 values are 52.1 Omega and 71.0 Omega for the photoanodes made of vertically aligned nanorod-like rutile TiO2 single crystal nanowire bundles and the vertically aligned anatase TiO2 nanotubes, respectively. The lower R-0 of the rutile TiO2 photoanode means a superior photoelectron transfer property. XPS valence-band spectra analysis indicates that the nanorod-like rutile TiO2 film has almost identical valence band position (1.95 eV) when compared to the anatase TiO2 nanotube film, meaning a similar oxidation capability, further confirming the superior photoelectron transport property of the nanorod-like rutile TiO2 single crystal nanowire bundles.