High-capacitance MnO2 nanoflakes on preformed C/TiO2 shell/core nanowire arrays for electrochemical energy storage

In this work, MnO2 nanoflakes are electrochemically deposited on preformed C/TiO2 shell/core nanowire arrays to form a shell/shell/core arrays electrode (MnO2/C/TiO2). Their structure and surface morphology are studied by using X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. The results suggest that MnO2 nanoflakes have well-distributed covered on the surface of C/TiO2 shell/core nanowire arrays. The MnO2/C/TiO2 shell/shell/core arrays are evaluated as a supercapacitor electrode material, which exhibits high specific capacitance of 639 F g−1 at a charge/discharge current density of 1 A g−1 and 78.7% specific capacitance retained after 1000 cycles. The superior pseudo-capacitive properties are attributed to the unique shell/shell/core structure for easy access of electrolyte ions, large surface to volume and high electrochemical activity. Our result shows that three-dimensional hierarchical nanostructures are being regarded advantageous for electrochemical energy applications.