TiO2 nanotube arrays were fabricated using electrochemical anodization process and post-treated by varying the concentration of the TiCl4 aquous solution (5 to 50 mM) for the surface treatment. Those photoelectrochemical (PEC) performances were significantly influenced by the TiCl4 concentration. The 20 mM TiCl4-treated TiO2 nanotubes exhibited significantly enhanced PEC response, due to efficient passivation of the surface recombination traps. However, as the TiCl4 concentration increased further to 50 mM, its PEC performance was reduced back, despite higher surface area. It can be attributed to the blocked voids caused by the formation of the TiO2 nanoparticles between the TiO2 nanotubes, because it leads to the hindered ion transport.