Vertically aligned nanorod-like rutileTiO2 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.