Supramolecule-assisted synthesis of in-situ carbon-coated MnO2 nanosphere for supercapacitors

Inspired by the supramolcular chemistry assembly theory, carbon-coated MnO2 nanospheres (C@MnO2) were successfully synthesized by a two-step method. First, the supramolecular solution was prepared by beta-cyclodextrin inclusion of manganese acetate, which was then treated by a hydrothermal reaction and the calcination in the following. The scan electron microscopy (SEM) and transmission electron microscopy (TEM) images present that the C@MnO2 composites have the nanosphere morphology, in which the carbon layer originated from the carbonization of beta-cyclodextrin was uniformly coated on the MnO2 nanoparticles. The electrochemical characteristics were examined by galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results demonstrated that C@MnO2 exhibited high specific capacitance (396.4 F g(-1) at 2 A g(-1) ) and good rate capability. In addition, 84.1% of the initial capacitance was maintained after 10000 cycles, indicating the excellent electrochemical stability. The superior electrochemical performance of the C@MnO2 was attributed to the outstanding uniform nanospheres structure that facilitates ion mobility and the synergistic effect between conductive carbon and pseudocapacitive MnO2. Hence, C@MnO2 can be a potential candidate material for the applications in supercapacitors. (C) 2018 Elsevier B.V. All rights reserved.