Electrochemically synthesized conducting polypyrrole for energy conversion, storage and gas sensor applications

• Main Author: Manzano, Maria Carla F.
• Format: text
• Language: English
• Published: Animo Repository 2016
• Subjects: Supercapacitors—Design and construction; Photovoltaic power generation; Energy conversion; Polymers; Physics
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/483
• Institution: De La Salle University

The versatility of conducting polymers in many device applications was demonstrated in the design and fabrication of three polypyrrole-based devices, namely supercapacitor, photovoltaic capacitor, and gas sensor. All three devices utilized, as an active component, the conducting polymer polypyrrole (Ppy) prepared by electrochemical deposition.In this paper, a prototype supercapacitor was designed and fabricated using electrochemically synthesized conducting polypyrrole films as electrodes. The specific capacitances obtained in this study range from 18.7 to 55.6 F/g which is slightly higher than that obtained for commercial supercapacitors with activated carbon electrodes whose maximum range from 20 to 50 F/g. When subjected to cycle life test, the specific capacitance of the Ppy film electrodes stabilized after 10 cycles and was found to be highly stable up to 100 cycles with only 1% decrease in specific capacitance. The stabilization time of the Ppy film electrodes in this study are shorter than those from similar studies in which stabilization was only obtained after 100 cycles. Finally, the measured charging time for the prototype supercapacitor was 5 minutes, attaining a voltage of 1.26V.Another device designed and fabricated in this study is a conducting Ppy-based photovoltaic capacitor. While a conventional solar cell converts solar to electrical energy, the photovoltaic capacitor reported in this study is able to convert solar to electrical energy whilst storing it in the same device. The photovoltaic capacitor devices are in a sandwich type arrangement in wet and solution-filled configurations. Measured open-circuit voltages (VOC) range from 0.665V to 1.128V under illumination from a halogen lamp. The solution injected photovoltaic devices designed and fabricated using device configuration 3 produced VOC ranging from 0.850V to 0.930V, a maximum short-circuit current (ISC) of 7.35 mA and efficiency of 0.65% under 100W/m2 solar intensity. It is expected that higher efficiencies can be achieved under standard solar illumination of 1000W/m2 used in solar cell performance tests. Furthermore, the photovoltaic devices showed characteristics of a supercapacitor based on its structure and on its charging pattern. The measured open circuit voltages in this study are higher than those of commercial silicon-based solar cells (VOC is 0.6V at one sun, i.e. 1000W/m2), and comparable to GaAs-based solar cells (VOC is 1.15V).Aside from energy conversion and storage, conducting polymers have potential applications as gas sensors. The advantage of conducting polymer-based gas sensors over their metal-oxide counterparts is that they have higher sensitivities and shorter response time. This study has shown that electrochemical synthesis of conducting polypyrrole films is a relatively simple and economical method of producing highly sensitive active materials for ethanol vapor sensing. The fractional change in resistance of the conducting Ppy films fabricated in this study was measured to be as high as 91% upon exposure to 250ppm ethanol vapor.