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

Abstract

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 n-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.