Construction of TiO2 Nanotubes/C/MnO2 Composite Films as a Binder-Free Electrode for a High-Performance Supercapacitor

Although titanium dioxide (TiO2) exhibits excellent promise in electrode materials for supercapacitors, its poor conductivity and low areal specific capacitance hamper further development. In this work, we have designed a clever way to deposit manganese dioxide (MnO2) in order to improve its electrochemical performance via a facile and typical hydrothermal method. In a hydrothermal process, carbon (C), which deposited via new gas thermal penetration, acts as a reducing agent, while a potassium permanganate (KMnO4) solution acts as an oxidant. In this way, MnO2, which has a high theoretical capacity, is generated on TiO2 nanotube arrays (denoted as TNTs) successfully. Remarkably, a TNTs/C/MnO2 film prepared at a hydrothermal temperature of 90 degrees C and 0.3 g of KMnO4 revealed a superior electrochemical property with 55 mF/cm(2) areal capacitance at a scan rate of 5 mV/s, 23 times more enhanced than that of a TNTs/C film. Also, the energy density of a TNTs/C/MnO2 film reached 46.8 Wh/cm(2) when the power density was 0.12 mW/cm(2), and the energy density still remained at 22.4 Wh/cm(2) at a high power density of 0.8 mW/cm(2). After 1000 cycle tests, 93.2% capacitance was still retained, indicating excellent reversibility and cycle stability of TNTs/C/MnO2 electrode. This work opens up a facile path for efficient growth of electrode materials with high performance for energy storage devices.