Ionic liquid (IL) capped MnO2 nanoparticles as an electrode material and IL as electrolyte for supercapacitor application

In this work, an ionic liquid (IL) based electrode material was synthesized for the supercapacitor application. Initially, manganese dioxide (MnO2) nanoparticles have been prepared by a sol-gel method using IL, Aliquat HTA-1 as a capping agent. The effect of IL on the morphology of MnO2 nanoparticles has been investigated by using scanning and transmission electron microscopy. The morphology reveals formation of the nanorods in presence of IL and spherical nanoparticles in absence of IL. The X-ray diffraction measurements disclose a tetragonal crystal structure pattern of alpha-MnO2 with a crystallite size of about 20 nm. Optical properties of MnO2 have been studied by UV-Vis and emission spectroscopy. The emission spectra of MnO2 in presence of IL exhibits emission band which shows a red shift by 30 nm. The supercapacitor study has been carried out using cyclic voltammetry, and charge-discharge with MnO2 as an electrode material and 5% IL as supporting electrolyte. As evidenced by the electrochemical measurements, the MnO2 with IL generates a substantial pseudocapacitance reaching a maximum value of up to 453 Fg(-1). Moreover, the supercapacitor is assembled with IL capped MnO2 as a positive and a negative electrode which resulted in high specific capacitance and better rate capability. (C) 2018 Elsevier Ltd. All rights reserved.