Novel ZnO/NapTS/Ppy and GO/NapTS/Ppy electrode materials for supercapacitor applications

• Main Author: Alcantara, Norberto T.
• Format: text
• Language: English
• Published: Animo Repository 2020
• Subjects: Electrodes; Zinc oxide thin films; Physics
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/1407; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=2446&context=etd_doctoral
• Institution: De La Salle University

Galvanostatic and galvanodynamic methods of electrochemical deposition were employed to fabricate conducting polypyrrole (PPy) film electrodes for supercapacitor applications. In this method, the PPy film electrodes were electrochemically synthesized in an aqueous solution containing 0.10M pyrrole as monomer and various dopants, i.e. sodium p-toluenesulfonate (Na-pTS) and hydroquinone monosulfate potassium salt (HQS-K), and co-dopants oxalic acid (Ox), zinc oxide (ZnO), and graphene oxide (GO). A two-electrode electrochemical cell was used, and for counter and working electrodes, stainless-steel plates. The applied current density during synthesis was kept at 4mA/cm2 with varying duty cycle of 25%, 50%, 75% and 100%, respectively.The thickness and surface morphology of the PPy films grown were obtained using scanning electron microscopy (SEM). The Ox/HQS-K/PPy films have average thickness ranging from 3.22μm to 24.50 μm. For GO/NapTS/PPy films, thickness ranged 26 μm to 172.5 μm; and for ZnO/NapTS/PPy films, 30.60 μm to 1688.0 μm. The SEM images obtained show star-like microstructures on the surface of Ox/HQS-K/PPy films grown at 50% duty cycle. On the other hand, the morphology of GO/NapTS/PPy films show nano- flake structures and their cross-sections are sponge-like. The surface morphology of ZnO/Na-pTS/PPy films synthesized at constant current (100% duty cycle) exhibit lamellar and spherulite structures associated with increased conductivity. The measured AC resistance of the PPy films ranged from 0.59 Ω to 4.0 Ω, with the PPy films synthesized at 100% duty cycle showing the lowest AC resistance.Using cyclic voltammetry, the capacitance, gravimetric and areal capacitances of the PPy films were determined. The capacitance values obtained were found to be dependent on the synthesis duty cycle. In this study, pulse-polymerized PPy film electrodes were found to have higher capacitance and stability than those synthesized at constant current. The ZnO/NapTS/PPy film grown at 75% duty cycle showed the highest gravimetric capacitance at 14.7 F/g. Furthermore, the ZnO/NapTS/PPy film electrodes were found to be more stable than GO/NapTS/PPy film electrodes, with an 85.8% retention in capacitance after 300 cycles and 80.2% after 500 cycles. Among the GO/NapTS/PPy film electrodes, the film that was pulse-polymerized at 50% duty cycle showed the highest gravimetric capacitance (14.1 F/g).Prototype storage devices were fabricated using a sandwich-type configuration consisting of several layers that includes the ZnO/NapTS/PPy film electrodes and a nano- cellulose film separator soaked in 1.0M NaCl solution. It was deduced that a capattery was created based on the devices’ built-in emf and the electrochemical behavior/performance of the electrodes.