Three-dimensional hierarchical graphene/TiO2 composite as high-performance electrode for supercapacitor

Three-dimensional (3D) hierarchical graphene/TiO2 composite is fabricated by in-situ preparation of mesoporous TiO2 on the 3D graphene (3DG) framework. The 3D graphene/TiO2 (3DG/TiO2) composite exhibits a hierarchical three-dimensional porous structure with mesopore (3.5 nm), macropore (several tens of micrometers to 200 μm) and a high specific surface area (171 m2 g−1). When used as electrodes for supercapacitor, the 3D graphene/TiO2 composite electrode delivers a specific capacitance of 235.6 F g−1 at 0.5 A g−1, whereas that of 3D graphene is 160.4 F g−1. Furthermore, the 3D graphene/TiO2 electrode exhibits acceptable rate capability (86% capacitance retention at 2 A g−1), and satisfactory cycling stability. Asymmetric supercapacitor was further assembled based on the 3DG/TiO2 and activated carbon electrodes. The device possesses a specific capacitance of 64.9 F g−1 at 0.2 A g−1. This improved electrochemical capacitive performance is mainly owing to the synergistic effects between graphene and TiO2, and the hierarchical three-dimensional porous structure.