Tailored TiO2-SrTiO3 heterostructure nanotube arrays for improved photoelectrochemical performance

TiO2 nanotube arrays formed on Ti substrate by electrochemical anodization have been converted into TiO2−SrTiO3 heterostructures by controlled substitution of Sr under hydrothermal conditions. The growth of SrTiO3 crystallites on the nanotube array electrode was probed by electron microscopy and X-ray diffraction. As the degree of Sr substitution increases with the duration of hydrothermal treatment, an increase in the size of SrTiO3 crystallites was observed. Consequently, with increasing SrTiO3 fraction in the TiO2−SrTiO3 nanotube arrays, we observed a shift in the flat band potential to more negative potentials, thus confirming the influence of SrTiO3 in the modification of the photoelectrochemical properties. The TiO2−SrTiO3 composite heterostructures obtained with 1 h or less hydrothermal treatment exhibit the best photoelectrochemical performance with nearly 100% increase in external quantum efficiency at 360 nm. The results presented here provide a convenient way to tailor the photoelectrochemical properties of TiO2−SrTiO3 nanotube array electrodes and employ them for dye- or quantum-dot-sensitized solar cells and/or photocatalytic hydrogen production.