Dispositivos de armazenamento de energia e monitoramento de pH baseados em compósitos de polianilina e polipirrol

Abstract

The increase in the use of energy demands the search for new energy storage devices that have good cycle life and high power and energy density. In order to meet this need, modified electrodes with supercapacitative properties have been developed. The present work deals with the obtaining of conducting polymer modified electrodes from different techniques for application in energy storage devices. Chapter 1 describes the use of the Layer-by-Layer (LbL) technique for modification of ITO electrodes with graphene oxide (OG) and polyaniline gum arabic (PANI-GA) electrodes. The concentration of gum arabic (GA) in the composite was optimized by electrochemical techniques, obtaining the best ratio of GA:PANI (1:1), in proportion (m / V). Characterization of LbL film (PANI-GA / OG)n (where n= number of bilayers) was performed by different techniques such as UV-Vis, FTIR, Raman, TEM, SEM, VC, EIE and chronoamperometry. The obtained films presented good stability in the chronoamperometry studies after some cycles of galvanostatic charge and discharge curves (CGCD), with increase of the supercapacitive properties as a function of the number of bilayers. The LbL film (PANI-GA / OG)15 showed CS of 12.81 mF cm-2 (j = 0.1 mA cm-2) and 72.8% CS retention after 1000 cycles of CGCD. The properties of (PANI-GA / OG)3 LbL film as a pH sensor was also investigated which presented a linear range (R2 = 0.9915) for pH values from 2 to 7. Chapter 2 describes the electrode modification by electrochemical polymerization of polypyrrole and polyaniline on the polished carbon graphite (CG) surface from depleted cells, designated CG/PPY/PANI. The electrochemical parameters for CG electrode modification were optimized considering the electrochemical response by the VC and CGCD. The optimized conditions for CG electrode area expansion were E = 2.0 V and t = 750 s, for PPY polymerization were E = 1.0 V and q = 750 mC and for PANI electropolymerization, E = 0.8 V and q = 3 C. The modified CG / PPY / PANI electrode presented better electrochemical results compared to the CG / PPY and CG / PANI electrodes. EIS results for GC/PPY/PANI showed the pseudocapacitive behavior of the electrode and, from CGCD, CS= 3416 mF cm-2 (j = 2 mA cm-2) and 76% capacitance retention after 850 CGCD cycles were obtained. The optimized electrode was characterized by FTIR, Raman and SEM / FEG, evidencing the modification of the CG surface. SEM/FEG images present the globular structures characteristic of conducting polymer electrodeposited. The modified CG/PPY/PANI electrode presented electrochemical properties, such as stability and specific capacitance, which make it promising for application in energy storage devices.