Desenvolvimento de um pseudocapacitor eletroquímico baseado em eletrodos de polianilina e lignina

Abstract

This work presents an applied investigation into the development of composite materials to be used in an electrochemical supercapacitor. The research is grounded in the justification that there is a growing demand for efficient and more sustainable solutions in the energy sector, making it necessary to evaluate alternative materials capable of ensuring good performance in electrochemical devices while reducing environmental impacts. Accordingly, the composites addressed in this study are fabricated from low-cost materials suitable for application in electrochemical devices and with low environmental impact, such as polyaniline, lignin, carbon black, and paraffin. The main objective was to develop a composite that would exhibit improved electrochemical response through cyclic voltammetry tests for use as an electrode in an electrochemical supercapacitor. To achieve this, the methodology involved preparing composites with different proportions of constituent materials (polyaniline, lignin, carbon black, and paraffin), followed by cyclic voltammetry tests in a threeelectrode system, as well as thermal crosslinking of the most promising composites and subsequent comparison between crosslinked and non-crosslinked samples. Considering the effects of swelling and deswelling, cumulative mechanical stress, and the resulting loss of electrical contact between the composite material and the current collector surface during cyclic voltammetry, it was not possible to obtain results that demonstrated a true response, in terms of specific capacitance, for each composite. Due to these effects, it was not possible to rigorously establish which of the most promising composites (K, I, H, and F) presents superior performance for application in electrochemical pseudocapacitors. For this reason, thermal crosslinking of these composite materials was carried out. The results indicated that the crosslinked composites K, I, H, and F exhibited greater mechanical stability at the expense of their specific capacitance when compared to their non-crosslinked counterparts over several cycles. Even with thermal treatment, the results showed that the effects of swelling and deswelling remain evident. It is concluded that, although the developed composites (K, I, H, and F, as well as their crosslinked versions) are promising for application in electrochemical pseudocapacitors, the phenomena of swelling, deswelling, and cumulative mechanical stress compromise the precise determination of the specific capacitance and cycling stability of each composite. Thermal crosslinking may have provided greater mechanical stability but did not significantly mitigate these physicochemical phenomena. Therefore, a rigorous evaluation of the specific capacitance and cycling stability of composites K, I, H, and F requires the adoption of additional experimental strategies capable of mitigating or circumventing these effects.