The interlocked in situ fabrication of graphene@prussian blue nanocomposite as high-performance supercapacitor

Abstract

High-quality graphene@prussian blue (G@PB) nanocomposite sheets have been successfully fabricated via a one-step in situ hydrothermal method, in which uniform PB nanoparticles completely covered both sides of graphene sheets through control of the etching of the raw material and growth of the target products. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) demonstrated effective combination. A series of G@PB nanocomposite sheets with different graphene contents as well as other PB/carbonaceous composites and mixed G@PB materials provided adequate proof for the synergetic effect of graphene and Prussian blue in G@PB nanocomposite sheets as well as the important effect of each composite on the electrochemical performance; graphene not only prevented the agglomeration of PB nanoparticles but also provided conductive network for fast electron transport, which was verified by the IR voltage drop and EIS test. In particular, the G@PB-5 hybrid composite showed the highest capacitance of 388.09 F g⁻¹ at a current density of 1 A g⁻¹ and enhanced rate capability and long-term stability with 97.2% retention over 5000 cycles as well as coulombic efficiency of nearly 100%. Asymmetric supercapacitor cells were assembled by pairing an optimized nanocomposite electrode with an activated carbon negative electrode, which displayed a reversible operating voltage of 2.0 V. These high electrochemical performances render the G@PB-5 nanocomposite sheets promising for energy-storage hybrid electrodes.