Self-assembly of ultrathin MnO2/graphene with three-dimension hierarchical structure by ultrasonic-assisted co-precipitation method

Abstract Hierarchical ultrathin nanostructure MnO 2 on graphene sheets are first prepared through ultrasonic-assisted co-precipitation method. The possible growth mechanism of the nanocomposite is discussed by monitoring the early growth stages. It is shown that the formation of the hierarchical structure MnO 2 follows a typical self-assembly and Ostwald ripening process. The dispersion of nanoscale thin MnO 2 flakes with thicknesses of about 5–10 nm on the graphene helped to increase the contact area of MnO 2 with electrolyte, reduce the diffusion and migration length of the ions and increase the electrochemical utilization of MnO 2 . Electrochemical characterization demonstrate that the hierarchical MnO 2 /graphene are capable of delivering specific capacitance of 216 F g −1 at the current density of 1 A g −1 . A capacity retention of 89.3% can be maintained after 2000 continuous charge–discharge cycles. The method provides a facile and straightforward approach to synthesize hierarchical of MnO 2 onto the graphene and may be readily extended to the preparation of other classes of hybrids based on graphene sheets for technological applications.