Energy storage is currently one of the most significant technological challenges globally, and supercapacitor is a prominent candidate over batteries due to its ability for fast charging and long lifetime. Supercapacitors typically use porous carbon as electrodes, because of both the high conductivity and surface area of the material. However, the state-of-the-art porous carbon described in the literature uses toxic chemicals and complex procedures that enhance costs and pollute the environment. Thus, a more sustainable procedure to produce porous carbon is highly desirable. In this context, xerogel-like carbons were prepared by a new, cheap, simple route to polymerization reactions of tannin-formaldehyde in a bio-oil by-product. Using bio-oil in its natural pH allowed a cost reduction and avoided using new reactants to change the reactional medium. Textural properties and electrochemical performances were improved by fast activating the material per 20 min. The non-activated carbon xerogel presented a capacitance of 92 F/g, while the activated one had 132 F/g, given that 77% of the components used are eco-friendly. These results demonstrate that renewable materials may find applications as carbon electrodes for supercapacitors. Overhauling the synthesis route with a different pH or replacing formaldehyde may enhance performance or provide a 100% sustainable carbon electrode.
A procura de produtos ambientalmente amigáveis, com obtenção a partir de fontes facilmente renováveis e de fácil acesso, menor custo, biodegradáveis, menos agressivos à saúde humana, entre outros, levou ao desenvolvimento de tecnologias empregando corantes naturais. Neste trabalho desenvolve-se uma breve revisão sobre corantes naturais, classificação e procedência, suas propriedades químicas e estruturais e discute-se a aplicação destes corantes em dispositivos como células solares - OPVCs (Organic Photovoltaic Cells), células solares sensibilizadas por corante –DSSCs (Dye Sensitized Solar Cells) e diodos emissores de luz – OLEDs (Organic Light Emitters Diodes) entre várias outras aplicações.
Carbon material is the largest material used as electrode on advanced energy storage devices. The modern lifestyle requires more energy, consequently, more smart energy use and efficient devices are needed. The constant evolution of materials technologies looking for green material and renewable raw material, that have minimal impact on the environment, is one of the most important subjects studied in recent years. The scientific and industry community are paying more attention to new forms of carbon such as nanotubes, graphene, and activated carbon fiber. The purpose of this work is to convert human hair into a hollow carbon filament to be used as a supercapacitor electrode. The human hair needs 3 stages to be converted into carbon filament: textile manufacture, oxidation, and carbonization. The electrochemical behavior was analyzed in a threeelectrode electrochemical cell system with 2 M of H 2 SO 4 electrolyte medium. The behavior of the electrode was characterized electrochemically by galvanostatic charge/discharge curves, cyclic voltammetry, and electrochemical impedance spectroscopy, showing 163 F g -1 of a maximum value of specific capacitance.
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