One-step preparation of single-crystalline Fe2O3 particles/graphene composite hydrogels as high performance anode materials for supercapacitors

To increase the energy density of supercapacitors to approach that of batteries, the current research is always directed towards the cathode materials, whereas the anode materials are rarely studied. In the present work, single-crystalline Fe2O3 nanoparticles directly grown on graphene hydrogels are investigated as high performance anode materials for supercapacitors. During the formation of the graphene/Fe2O3 composite hydrogels, flexible graphene sheets decorated with Fe2O3 particles are self-assembled to form interconnected porous microstructures with high specific surface area, which strongly facilitate charge and ion transport in the full electrode. Infrared spectra show that hydrogen bond is formed between C-OH on graphene hydrogels and Fe2O3. Benefits from the combined graphene hydrogels and Fe2O3 particles in such a unique structure are that the graphene/Fe2O3 composite electrode exhibits an ultrahigh specific capacitance of 908 F g(-1) at 2 A g(-1) within the potential range from -1.05 to -0.3 V, and an outstanding rate capability (69% capacity retention at 50 A g(-1)). Furthermore, the cycling performance is clearly much better for the graphene/Fe2O3 composite hydrogels than that for pure Fe2O3 sample. These findings open a new pathway to the design and fabrication of three-dimensional graphene hydrogel composites as anode materials in the development of high-performance energy-storage systems. (C) 2014 Elsevier Ltd. All rights reserved.