Abstract
Three dimensional hierarchical metal oxide nanostructures, like TiO2 nanowire arrays, have attracted great attention for electrochemical energy conversion and storage applications. The functionality of such devices can be further enhanced by adding a nanowire shell with a different stoichiometry or composition compared to the core. Here, we report an approach with a facile heat treatment at 1050 °C, which allows the fabrication of rutile TiO2–SiOx core-shell nanowire arrays on silicon substrates. Our detailed electron microscopic investigation shows that this method is able to cover hydrothermally grown rutile TiO2 nanowires with a uniform shell of several nanometers in thickness. Moreover, the treatment improves the quality of the rutile TiO2 core by removing lattice defects, introduced from the hydrothermal growth. Electron energy loss spectroscopy reveals that the homogeneous shell around the TiO2 core consists of amorphous SiOx and does not form any intermediate phase with TiO2 at the interface. Thus, the properties of the TiO2 core are not affected by the shell, while the shell suppresses undesired electron back transfer. Latter leads to performance losses in many applications, e.g., dye sensitized solar cells, and is the main reason for a fast degradation of devices incorporating organic materials and TiO2.
Highlights
TiO2 nanowires (NWs) combine the versatility of TiO2 with the unique properties of 1D nanostructures, e.g., directed electron path and large surface area
TiO2–SiOx core-shell NW arrays were prepared by a heat treatment of TiO2 NWs, which were hydrothermally grown on Si substrates
The morphology of the NW arrays was investigated by scanning electron microscopy (SEM) with a Zeiss CrossBeam 1540XB field emission SEM operated at 5 kV using an in-lens detector
Summary
TiO2 nanowires (NWs) combine the versatility of TiO2 with the unique properties of 1D nanostructures, e.g., directed electron path and large surface area. TiO2–SiOx core-shell NW arrays were prepared by a heat treatment of TiO2 NWs, which were hydrothermally grown on Si substrates.
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