Anodic TiO2 nanotube arrays (ATNAs) have been one of the promising electrode materials for supercapacitors due to good chemical stability, large surface area and simple fabrication method. However, the specific capacitance of ATNAs is generally low. Here, we focus on the hydrothermal treatments of ATNAs in (NH4)(2)TiF6 dilute solutions. After the (NH4)(2)TiF6 hydrothermal treatments, the smooth wall of ATNAs became rough, a layer of nanoparticles were generated on the surface of nanotubes concurrently. The specific capacitance of the hydrothermally treated ATNAs increased remarkably due to the special nanostructure composed of rough tube walls and the nanoparticles embedded on the tube walls. After the hydrothermal treatment in 0.01 M (NH4)(2)TiF6 aqueous solution at 120 degrees C for 45 min, the ATNAs exhibit a specific capacitance of 31.12 mF cm(-2), about a 3.1-fold improvement over the untreated ones. (C) 2017 Elsevier Ltd. All rights reserved.