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

A facile method has been developed to construct polyaniline@MnO2/graphene ternary hybrid hollow spheres via Pickering emulsion polymerization. In our strategy, MnO2-decorated graphene (MnO2/GR) has been first prepared and employed as a Pickering emulsifier to stabilize an oil-phase-containing aniline. Upon the polymerization of aniline at the oil/water interface, polyaniline@MnO2/graphene hollow sphere (PANI@MnO2/GR HS) was generated. The influences of wettability and concentration of MnO2/GR, the volume ratios of oil to water on the Pickering emulsion, have been systematically investigated. The structure of the as-prepared PANI@MnO2/GR HS has been proven by Raman, FTIR, SEM, and TGA. With the unique hollow structure and synergetic contributions from PANI, MnO2, and graphene, the electrochemical performance of our PANI@MnO2/GR HS has been significantly improved compared to that of the stacked two-dimensional PANI@MnO2/GR composite. The maximum specific capacitance of PANI@MnO2/GR HS reaches 743.8 F g–1, and high capacitance retention (82.5% from 0.5 to 10 A g–1) is also displayed, suggesting the outstanding electrochemical performance. In addition, our PANI@MnO2/GR HS also demonstrates good cycling stability, which retains 93% of the initial value after 2000 cycles.