Reduced graphene oxide decorated on MnO2 nanoflakes grown on C/TiO2 nanowire arrays for electrochemical energy storage

Abstract

In this work, RGO is decorated on MnO₂ nanoflakes, which are electrochemically deposited on preformed C/TiO₂ shell/core nanowire arrays to form a RGO/MnO₂/C/TiO₂ shell/core array electrode. Their structure and surface morphology are studied using X-ray diffraction analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman microscopy, scanning electron microscopy and transmission electron microscopy. The results suggest that a RGO layer was coated on the MnO₂ nanoflakes, and the MnO₂ nanoflakes have a well-distributed coverage on the surface of the C/TiO₂ shell/core nanowire arrays. The RGO/MnO₂/C/TiO₂ shell/core arrays are evaluated as a supercapacitor electrode material, which exhibits a high specific capacitance of 822.3 F g⁻¹ at a charge/discharge current density of 1 A g⁻¹ and 87.4% specific capacitance retention after 5000 cycles. The superior pseudo-capacitive properties may be due to the unique shell/core structure and the decoration of RGO. The RGO decorated on MnO₂ can provide partial double-layer capacitance; on the other hand, the RGO can improve the electrical conductivity of the electrode and alleviate the volume change of MnO₂ during charge/discharge processes given its mechanical flexibility. Our results show that the RGO/MnO₂/C/TiO₂ electrode can be regarded as advantageous for electrochemical energy applications.