Synthesis and structure modification of titania nanotubes for energy conversion

Pure and zinc (Zn)-doped titania nanotubes (TNTs) were fabricated by means of the anodization method which was carried out in a mixture of electrolytes prepared by combining ethylene glycol (EG), ammonium fluoride (0.3 wt NH4F), and de-ionized water (2 Vol% H2O) with 1 wt%, 2 wt%, and 3 wt% concentrations of dopant zinc fluoride (ZnF2). A constant dc power supply of 50 V was used as anodic voltage. Anodized samples were annealed at 450 C for 2 hours. The resultant samples were characterized by several techniques, x-ray diffraction (XRD) for structure and phase analysis, scanning electron microscopy (SEM) for surface morphology, and x-ray photoelectron spectroscopy (XPS) for chemical composition analysis. The results showed that the diameters and thicknesses of titanium dioxide (TiO2) NTs were about 66 nm and 15 nm respectively. The efficiency of the dye-sensitized solar cells made from Zn-doped TiO2 NTs was 4.54% under illumination of 100 nW/cm2 when 1 wt% of ZnF2 dopant was used.