Morphological Modulation of TiO2 Nanotube via Optimal Anodization Condition for Solar Water Oxidation

Abstract

<p>With the depletion of fossil fuels and the rising global demand for energy, photoelectrochemical (PEC) water splitting presents a promising solution to avert an energy crisis. Titanium dioxide (TiO₂), an <italic>n</italic>-type semiconductor, has gained popularity as a photoanode due to its remarkable PEC properties. Nevertheless, inherent challenges such as a wide band gap (~3.2 eV), charge recombination, and slow oxygen evolution reaction (OER) rates at the surface limit its practical application by constraining light absorption. To overcome these limitations, we have developed TiO₂ nanotubes (NTs) using a facile anodization method. This study examines the impact of anodization growth parameters on solar water oxidation performance. Specifically, TiO₂ NTs with modified anodization time (referred to as TiO₂-6) showed a 3.5-fold increase in photocurrent density compared to the as-grown TiO₂ NTs. Furthermore, electrochemical analyses, such as electrochemical impedance spectroscopy (EIS), indicated a significant decrease in charge transfer resistance following the adjustment of on-off anodization time. Additionally, the TiO₂-6 photoanode demonstrated a higher electrochemically active surface area (ECSA) than other samples. Therefore, optimal nanostructuring parameters are crucial for enhancing the PEC properties of TiO₂ NTs. Overall, our findings offer valuable insights for fabricating high-quality TiO₂ NTs photoanodes, contributing to developing efficient PEC systems for sustainable energy production.</p>