H–TiO₂/C/MnO₂ nanocomposite materials for high-performance supercapacitors

Functionalized TiO₂ nanotube arrays with decoration of MnO₂ nanoparticles (denoted as H–TiO₂/C/MnO₂) have been synthesized in the application of electrochemical capacitors. To improve both areal and gravimetric capacitance, hydrogen treatment and carbon coating process were conducted on TiO₂ nanotube arrays. By scanning electron microscopy and X-ray photoelectron spectroscopy, it is confirmed that the nanostructure is formed by the uniform incorporation of MnO₂ nanoparticles growing round the surface of the TiO₂ nanotube arrays. Impedance analysis proves that the enhanced capacitive is due to the decrease of charge transfer resistance and diffusion resistance. Electrochemical measurements performed on this H–TiO₂/C/MnO₂ nanocomposite when used as an electrode material for an electrochemical pseudocapacitor presents quasi-rectangular shaped cyclic voltammetry curves up to 100 mV/s, with a large specific capacitance (SC) of 299.8 F g⁻¹ at the current density of 0.5 A g⁻¹ in 1 M Na₂SO₄ electrolyte. More importantly, the electrode also exhibits long-term cycling stability, only ~13 % of SC loss after 2000 continuous charge–discharge cycles. Based on the concept of integrating active materials on highly ordered nanostructure framework, this method can be widely applied to the synthesis of high-performance electrode materials for energy storage.