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

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 °C and 0.3 g of KMnO₄ revealed a superior electrochemical property with 55 mF/cm² 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/cm² when the power density was 0.12 mW/cm², and the energy density still remained at 22.4 Wh/cm² at a high power density of 0.8 mW/cm². 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.