Controlled Structure and Growth Mechanism behind Hydrothermal Growth of TiO2 Nanorods

Fabrication of uniform vertically-aligned titanium dioxide nanorods (TiO2 NRs) was achieved by hydrothermal growth on a fluorine-doped tin oxide (FTO) glass substrate. The substrate was coated by a TiO2 seed layer composed of titanium (IV) butoxide (TBO) as a precursor in an HCl solution. To reduce the amount of toxic substances used in this work, a minimal amount of HCl was used. On a larger scale, this method would require less precursor and therefore be a cost-savings. The aim of the present work is to achieve high crystalline orientations of TiO2 NRs for low quantities of both TBO precursor and HCl solutions. Results showed that the 0.7% TBO TiO2 NRs after 1.5 h of hydrothermal treatment exhibited the optimal crystalline orientation along [001] while the (002) plane is the dominant facet. The results demonstrate high transmittance of visible light and well-formed crystalline structures that offer a fast electron pathway along the length of the TiO2 NRs with less grain boundaries. Lastly, TiO2 NRs and their growth mechanism are discussed. This work offers a promising hydrothermal method for growing well-aligned TiO2 single-crystal NRs that can be employed in solar cell applications.