Effect of NH4F and NaF in Ethylene Glycol Electrolytes for the Formation of TiO2 Nanotubes by Electrochemical Anodization

The application of highly ordered TiO2 nanotube arrays with a high surface-to-volume ratio as gas sensors, photoanodes in dye-sensitized solar cells, and materials for water photoelectrolysis is of great interest. It is among the compounds that material science has investigated the most. The aim of using NH4F and NaF in this study is to analyse the role of electrolytes in the morphology and organization of one-dimensional Titania nanotubes. Constant voltage (30 V), time (2 h), electrolyte concentration (0.5 wt % NaF/NH4F + ethylene glycol), calcination temperature (450 °C for 1 h), and water content (2 vol %) were employed for the fabrication of two distinct samples with NH4F and NaF at room temperature. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray absorption spectroscopy (EDAX), and X-ray diffraction (XRD) techniques analysed the morphology and structural properties of the synthesized nanotubes. The consistent, well-ordered, and well-separated structure of TiO2 nanotubes was credited with the outcome from FESEM results. XRD analysis confirms the anatase phase formation in the prepared samples and has shown significant changes in FWHM, crystallite size, lattice microstrain, and d-spacing. Additionally, optical properties were studied using the UV-Vis spectroscopy technique. DRS results revealed a significant change in the bandgap and absorption spectrum, discussed briefly in this study. We show from the studies that the electrolyte significantly affects the titania nanotubes’ optical and morphological properties, which helps analyse some exciting facts about using two different fluoride salts.