Polyaniline-graphene Hollow Spheres based on Graphene Stabilized Pickering Emulsions

Abstract

In recent years, hybrid nanomaterials of graphene and polyaniline have attracted extensive interest and have been considered as promising electrode materials for supercapacitor combining the advantages of both materials with synergistic effects. In contrast to the well-developed two-dimensional planar structure of graphene-PANI, the pursuit of hollow graphene-PANI hybrid structure is relatively less investigated. The hollow micro/nanostructured graphene-PANI materials with the nanoscale shell, inner cavity and pore structures, is highly expected to exhibit remarkable enhanced supercapacitor performance owing to the enhanced specific surface area and shortened diffusion length for both charge and mass transport. In this work, a novel kind of graphene-polyaniline hollow capsules (PANI-SGR HS) was prepared via Pickering emulsion polymerization using sulfonated graphene (SGR) as Pickering stabilizer. Amphiphilic sulfonated graphene is prepared by a covalent modification and used to stabilize oil phase containing aniline monomer. Aniline molecules were adsorbed to the oil-water interface owing to the electrostatic interaction between amino groups of aniline and sulfonic groups of SGR, which subsequently underwent interfacial polymerization at the oil/water interface upon the addition of initiator ammonium persulfate (APS). The effects of the sulfonation degree of graphene, the SGR concentration as well as the oil/water volume ratio on the stability and morphology of SGR stabilized emulsions were investigated in detail. The SGR with appropriate sulfonation degree can produce stable emulsions. The average diameter of the emulsion droplet decreased with the increasing concentration of SGR stabilizer. The emulsion stability can be improved with the increased water phase infraction. After polymerization of aniline and removal of the oil phase, three-dimensional hollow graphene-polyaniline sphere (PANI-SGR HS) was obtained. The morphology of PANI-SGR HS was observed by scanning electron microscopy (SEM). The special hollow sphere structure not only enlarged the liquid contact area but also improved charge carrier mobility. The hollow sphere modified electrode exhibited excellent performance with a specific capacitance of 480.59 F•g -1 at 1 A•g -1 , which is much higher than 251 F•g -1 of the common two-dimensional stacked graphene-polyaniline film. This novel three-dimensional PANI-SGR HS material may have potential applications in energy storage.

Synthesis of Polyaniline@MnO2/Graphene Ternary Hybrid Hollow Spheres via Pickering Emulsion Polymerization for Electrochemical Supercapacitors

“…However, the above employed LBL method and the sacrificial hard template were quite complicated and burdensome. Very recently, a simple, efficient, and controlled Pickering emulsion method was developed for constructing the graphene/PANI hollow sphere. , The as-prepared graphene/PANI hollow sphere exhibited a specific capacitance of 546 F g –1 , more than twice that of the two-dimensional stacked PANI/graphene composite. Considering the attractive electrochemical performance of graphene/PANI/MnO 2 ternary composites, it is highly expected that if MnO 2 could be introduced into the graphene/PANI hollow sphere, graphene/PANI/MnO 2 ternary hollow sphere with enhanced electrochemical utilization of graphene, MnO 2 , and PANI would be generated, which could provide high interaction area between active materials and electrolyte.…”