TiO2 photoanodes with exposed {0 1 0} facets grown by aerosol-assisted chemical vapor deposition of a titanium oxo/alkoxy cluster

Abstract

Photoelectrochemical water splitting is a promising technology for the development of solar fuels. Titanium dioxide (TiO₂) is one of the most studied metal oxides in this field as a photoanode. Achieving its full potential requires controlling its morphology and crystallinity and especially the exposure of its most active crystal facets. Herein, we present the formation of nanostructured TiO₂ photoanodes with anatase phase and high exposure of the {0 1 0} facet, the most active TiO₂ phase and facet. TiO₂ photoanodes were prepared from a Ti₇O₄(OEt)₂₀ titanium oxo/alkoxy cluster solution using aerosol assisted chemical vapor deposition. Characterization techniques such as SEM and TEM reveal that these TiO₂ photoanodes consist of morphologies resembling the crystals of gypsum, sand and water found in nature, also known as desert roses. Furthermore, TEM and XRD analysis also reveals that the metastable anatase TiO₂ phase is maintained up to 1000 °C and exceeds the typical anatase-to-rutile phase-transition temperature of 500–750 °C, a feature that could be exploited in the smart ceramics industry. Photoelectrochemical measurements show that these desert-rose TiO₂ photoanodes achieve excellent photocurrent densities with an incident photon-to-current efficiency of ∼100% at 350 nm and a faradaic efficiency for oxygen evolution of ∼90%.