Enhanced Charge Transfer Process in Morphology Restructured TiO₂ Nanotubes via Hydrochloric Acid Assisted One Step In-Situ Hydrothermal Approach

In this study, we demonstrate the enhanced photoelectrochemical (PEC) performance of the titanium foil based TiO₂ nanotube (TNT) array through a simple hydrothermal (HT) acid treatment method. The influence of hydrochloric acid (HCl) concentration variation in HT method on morphology and the photoelectrochemical performances of TNTs nanostructures were studied. Field Emission Scanning Electron Microscopy and X-ray powder diffraction results confirmed the morphology and crystal structure easily restructured during HCl assisted one step in-situ hydrothermal approach. The photocurrent density of optimized acid treated TiO₂ nanotube (TH-40) electrode was observed to be 2-times higher than the pristine TNT electrode. Thereafter, TH-40 sample exhibited noticeably photoelectrochemical solar hydrogen production of 66 μmol and 82 μmol in NaOH and Na₂S/Na₂SO₃ electrolytes respectively than the pristine TNT. The enhancement of photocatalytic activity was ascribed to the restructured morphology, as well as the efficient charge separation at rutile-anatase interface in the TH-40 sample as well as at the electrode-electrolyte interface. A hydrochloric acid assisted one step in-situ hydrothermal approach tailors the crystal structure and morphological features, which enhanced the photoelectrochemical properties of TiO₂ nanotube.