Study of composites of MnO2 and activated carbon for use as electrode material of hybrid supercapacitors

• Grant number: 18/19759-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2018
• End date: April 01, 2020
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Nerilso Bocchi
• Grantee: Samuel Henrique Mattoso
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated scholarship(s): 19/10772-7 - Electrochemical and material characterization of hybrid SP2/SP3 carbon powders for use in electrochemical power sources, BE.EP.IC

Abstract

Energy storage systems are becoming continuously more important in the present due to their growing usage in electro-electronic devices, electric cars and other technologies. In this context, supercapacitors are been studied in view of their intermediate properties in regards to the conventional energy storage systems, such as batteries and capacitors. Different materials like oxides, carbonaceous materials among others are being investigated. Hydrated and amorphous ruthenium dioxide is the most evaluated oxide due to its high theoretical and experimental specific capacitance. However, this oxide has disadvantages such as high cost and toxicity (non-environmentally friendly). Among the materials investigated to replace the ruthenium dioxide, manganese dioxide is a promising candidate, because of its high theoretical specific capacitance, low cost and also it is environmentally friendly. However, in relation to the values of electric conductivity and specific surface area, the manganese dioxide does not have comparable values such as those of ruthenium dioxide, being these two properties the most investigated. One of the ways to improve the conductivity of manganese dioxide is to mix it with carbonaceous materials, such as acetylene black. The resulting mixture has also a better charge collection due to the interaction between both species. Despite this, the acetylene black cannot contribute to increase the specific surface area, and causes the amount of electroactive material to be lower in the supercapacitor electrode. So, this project intends to prepare composite materials by mixing nanometric manganese dioxide, polyaniline activated carbon (PAC) and a binder agent (PVDF) in distinct mass proportions and evaluate their respective electrochemical performance as supercapacitor electrode materials. The project will include the synthesis of nanometric manganese, dioxide (MnO2), synthesis of polyaniline activated carbon (PAC), preparation of the composite electrodes and electrochemical characterizations. The MnO2 synthesis will be done using the microwave assisted hydrothermal methodology, with KMnO4 and acetone being the reactants. The PAC will be synthesized by carbonizing polyaniline doped with p-toluenesulfonate in a tubular furnace under N2 atmosphere and activated with KOH, followed by another heating under N2 atmosphere. The resulting material will be washed with a HCl solution. The composite materials will be prepared by mixing MnO2, PAC and PVDF in various proportions with cyclopentanone, leading to the formation of a slurry that will be applied on the platinum electrodes. These electrodes will be tested electrochemically by cyclic voltammetry and charge/discharge at constant current. For these tests, a conventional electrochemical cell will be used containing a previously prepared working electrode, a platinum blade as a counter electrode and a saturated calomel electrode as a reference electrode, immersed in a 0,1 mol L-1 Na2SO4 solution.