Stability of TiO2 nanotube arrays in photoelectrochemical studies

Photoelectrochemical (PEC) hydrogen generation gives an opportunity to acquire energy by means of clean and renewable resources such as water and solar light. A major problem in the PEC system is the stability of the photoanode material for long-term applications. Recently, self-assembled titanium dioxide (TiO2) semiconductors (and their hybrids) have shown potential to generate hydrogen in the PEC system. In the present investigation, stability of the nanotubular TiO2 in 1 M KOH solution under illumination conditions is investigated. The photoanode is found to be stable (in terms of activity and morphologically) for one month (8 h/day) without much change in the hydrogen generation rate. Possible photoelectrochemical reactions that can be responsible for degradation of performance of nanotubular TiO2 material are identified. Various spectroscopic and electrochemical measurements, viz., SEM, XRD, DRUV-Vis and Mott-Schottky are employed to confirm that the nanotubular TiO2 photoanode can be used for long-term applications. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.