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

Abstract

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 μm. 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 (R0) of the rutile TiO2 film via a simple photoelectrochemical method. Using this approach, the calculated R0 values are 52.1 Ω and 71.0 Ω 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 R0 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.