Hydrothermal solid-gas route to TiO2 nanoparticles/nanotube arrays for high-performance supercapacitors

Although TiO2 nanotube arrays (TNTAs) have shown great promise as supercapacitor materials, their specific capacitances are still not comparable with some typical materials. Here, TiO2 nanoparticles (NPs)/TNTAs hybrid structure has been derived from the anodized TNTAs by a facile hydrothermal solidgas method (HSGM), which can avoid cracking or curling of the TNTAs from Ti substrate. The obtained NPs/TNTAs hybrid structure can exhibit a -4.90 times increase in surface area and a -5.49 times increase in areal specific capacitance compared to the TNTAs without HSGM treatment. Besides, the argonatmosphere annealing can offer improved areal capacitance and cycling stability relative to the airatmosphere annealing. The hydrothermal vapor pressure is a key factor for controlling microscopic morphologies of TNTAs, the morphology transformations of TNTAs during the HSGM treatment can be accelerated under enhanced vapor pressures. The highest areal capacitance of HSGM-treated TNTAs is up to 76.12 mF cm(-2) at 0.5 mA cm(-2), well above that of any TiO2 materials reported to date. (C) 2017 Elsevier B.V. All rights reserved.