Facile interfacial synthesis of flower-like hierarchical a-MnO2 sub-microspherical superstructures constructed by two-dimension mesoporous nanosheets and their application in electrochemical capacitors

Abstract

In this work, flower-like hierarchical a-MnO₂ sub-microspherical superstructures were synthesized by means of a novel interfacial strategy, where the amphiphilic tri-block poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) was used both as a reaction material and a template in an acidic media. Further physical characterizations revealed that the flower-like MnO₂ hierarchical superstructures with a specific surface area of 216 m² g⁻¹ were assembled by two-dimension mesoporous nanosheet building blocks and greatly depended upon the synthesis condition. Electrochemical results demonstrated that the unique MnO₂ superstructures delivered a specific capacitance of 298 F g⁻¹ at a current density of 0.117 A g⁻¹, and even 236 F g⁻¹ at 2.353 A g⁻¹, demonstrating their great ability of delivering large energy density at high rates. The good electrochemical capacitance mainly resulted from their unique hierarchical porous structure and rich MnO₂-electrolyte interfaces. The unique hierarchical porous structure provided convenient ion transport paths for K⁺ ions to contact their rich electroactive sites for fast and efficient energy storage.