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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.86

Study of MnO2-Graphene Oxide nanocomposites for supercapacitor applications Rahul Singhal1*, Justin Fagnoni1, David Thorne1, Peter K. LeMaire1, Xavier Martinez2, Chen Zhao2, Ram K. Gupta2, David Uhl3, Ellen Scanley3, Christine C. Broadbridge3, Mani Manivannan4, Rishikesh Pandey5 1

Central Connecticut State University, New Britain, CT 06050, USA

2

Department of Chemistry, Pittsburg State University, Pittsburg, KS 66762, USA

3 Connecticut State Colleges and Universities (CSCU) Center for Nanotechnology, Southern Connecticut State University, New Haven, CT 06515, USA

4

Global Pragmatic Materials, Morgantown, WV 26508, USA

5 Connecticut Children's Innovation Center, University of Connecticut School of Medicine, Farmington, CT 06030, USA

ABSTRACT

Graphene oxide (GO)/MnO2 nanocomposites were synthesized by adding KMnO4 in a solution of water and ethanol (3:1), containing 10 mg of GO. Brown precipitates were obtained after a continuous stirring for 1 hr. The precipitates were then washed with deionized water (DI) water and dried to obtain the MnO2-GO nanocomposites. Pure MnO2 was also synthesized using the same method without GO for the comparison. X-ray diffraction pattern confirm δ-MnO2 type of MnO2 with birnessite type MnO2 structure. The TEM images show the average diameter of MnO2 nanorods as 15 nm. Electrochemical characterizations were carried out in an aqueous solution of 3M KOH. Charge-discharge studies were carried out between 1A/g to 20 A/g current range. The MnO2-GO nanocomposites showed improved electrochemical performances. The capacitance of MnO2 and MnO2-GO electrodes was found to be as 300 F/g, and 350 F/g, respectively at a current of 0.5 A/g. * Corresponding author: [email protected]; Ph. +1-860-832-2347

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INTRODUCTION In recent years, interest in the development of alternative energy storage/conversion devices with high power and high energy densities has increased due to current high energy demands. Electrochemical capacitors or supercapacitors are attracting wide attention, because of their high-power density, excellent reversibility, and long cycle life [1-4]. Many researchers have identified manganese dioxide (MnO2) as a promising material for supercapacitor applications because of its natural abundance, high theoretical capacity, low environmental toxicity, and cost-effectiveness [5-10]. In this paper, we report the synthesis, physical, and electrochemical characterization of MnO2 and MnO2-GO nanocomposite materials for supercapacitor applications. EXPERIMENTAL DETAILS The precursor materials, potassium permanganate (KMnO4) and ethanol (C2H6O), both obtained from Alfa Aesar, and the graphene oxide obtained from GraSpain, were used as received. To synthesize MnO2, the desired amo