Facile\nSynthesis of Three-Dimensional Sandwiched MnO₂@GCs@MnO₂ Hybrid Nanostructured Electrode for Electrochemical Capacitors

Abstract

Designable control over the morphology and structure\nof active materials is highly desirable for achieving high-performance\ndevices. Here, we develop a facile microwave-assisted synthesis to\ndecorate MnO₂ nanocrystals on three-dimensional (3D) graphite-like\ncapsules (GCs) to obtain sandwich nanostructures (3D MnO₂@GCs@MnO₂) as electrode materials for electrochemical\ncapacitors (ECs). A templated growth of the 3D GCs was carried out\nvia catalytic chemical vapor deposition and MnO₂ was decorated\non the exterior and interior surfaces of the GC walls through microwave\nirradiation to build an engineered architecture with robust structural\nand morphological stability. The unique sandwiched architecture has\na large interfacial surface area, and allows for rapid electrolyte\ndiffusion through its hollow/open framework and fast electronic motion\nvia the carbon backbone. Furthermore, the tough and rigid nature of\nGCs provides the necessary structural stability, and the strong synergy\nbetween MnO₂ and GCs leads to high electrochemical activity\nin both neutral (265.1 F/g at 0.5 A/g) and alkaline (390 F/g at 0.5\nA/g) electrolytes. The developed hybrid exhibits stable capacitance\nup to 6000 cycles in 1 M Na₂SO₄. The hybrid\nis a potential candidate for future ECs and the present study opens\nup an effective avenue to design hybrid materials for various applications.