Electrochemical properties of MnO2-deposited TiO2 nanotube arrays 3D composite electrode for supercapacitors

• MnO2 nanoparticles are electrodeposited into bamboo-like TiO2 nanotube arrays.
• MnO2 increases the reaction activity of the MnO2-TNTAs composite.
• Large inner surface offer many attachment sites for MnO2 to contact with electrolyte.
• MnO2-TNTAs exhibit better electrochemical properties than TNTAs.

The 3D composite electrode of MnO2-deposited TiO2 nanotube arrays (MnO2-TNTAs) for supercapacitors are prepared by a facile controllable electrodeposition of MnO2 in the bamboo-like TiO2 nanotubes (TNTAs). The effects of deposition current density on morphology evolution of the MnO2 phase were analyzed. It was found that an optimum deposition condition in terms of current density could be reached to achieve uniform crystal morphology of the deposited oxide phase. The results show that the TiO2 nanotube arrays synthesized by an anodization method consists of hollow bamboo-like tubes with a uniform inside diameter of 100–200 nm, a thickness of 10–20 nm and a length of 700–900 nm. At a low current, the MnO2 nanoparticles are considered to be deposited in the indentations in the tube walls, which increase the electrochemical activity of the TNTAs. The specific capacitance of optimized doses of MnO2-TNTAs achieves 40.4 mF/cm2, and the as-prepared MnO2-TNTAs exhibit better capacitance properties than TNTAs, this enhanced electrochemical activity is owing to the tubular structure of the TiO2 substrate with increased activity provides an increased reaction area and facilitates the contact of electrolyte with the active MnO2.

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