Preparation and pseudocapacitance properties of highly conductive sandwich-shaped MnO2/CNTs/MnO2 mesoporous materials
【Abstract】MnO2 is regarded as the most attractive electrode material for supercapacitor (SC) because of its low cost, non-toxic nature, high natural abundance, and superb theoretical specific capacitance. The tantalum capacitor electrode material MnO2 still has problems of poor conductivity and easy peeling during charging and discharging. In this study, a sandwich MnO2/CNTs/MnO2 mesoporous composite is fabricated by a facile galvanostatic electrochemical deposition approach on the surface of carbon paper pre-oxidized by nitric acid, and the middle layer of carbon nanotubes (CNTs) was added by a simple smear-drying method. The crystal structure, surface morphology, and pore characteristics of the sandwich composite are characterized by means of X-ray diffraction, scanning electron microscopy, and nitrogen adsorption test. The prepared composite shows a sandwich structure with mesopores of about 5 nm, which could ensure the efficient diffusion of electrolyte ions. Three-dimensional carbon paper could provide abundant conductive sites for attachment of MnO2. The synthesized α-MnO2 has a fluffy and porous morphology, which could reduce the expansion stress of the composite effectively. The intermediate layer of CNTs serves as conductive media relay between the inner and outer layers of MnO2 to further improve the conductivity of composite. The composite exhibits excellent electrochemical performance: the electrode has a reversible specific capacity of 428.8 F·g−1 at a current density of 0.1 A·g−1 and an outstanding specific capacitance retention of ca. 80% at 5 A·g−1. Moreover, the electrode still has an excellent cycle stability (95% retention rate) at a current density of 1 A·g−1 after 6 000 cycles.
【Keywords】 manganese dioxide; carbon nanotube; sandwich structure; composites; diffusion; electrochemical; supercapacitor;
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