We investigated the photo electrochemical characteristics of sodium-modified TiO₂ nanotube arrays. Vertically oriented TiO₂ nanotubes were developed by electrochemical anodizing titanium in a formamide solution containing ammonium fluoride. TiO₂ nanotube arrays were treated with sodium hydroxide solutions of various concentrations and then annealed in air. The resulting nanotube arrays were characterized via small angle X-ray diffractometer, diffuse reflectance spectroscopy, and electrochemical testing. The results showed that modification with sodium hydroxide was only confined to the nanotube surface and had little influence on both the crystal structure and the energy gap of the nanotubes. While, the photo electrochemical characteristics of the modified nanotube array electrodes indicated an enhanced photocurrent onset potential (E_onset) compared with pristine TiO₂ as well as better charge separation and transfer properties. Most importantly, these findings offer a simple and efficient way to design photo electrochemical cells that require no external energy input.