Bio-waste derived high performance and flexible en

To meet increasing demands for energy from sources other than fossil fuels, it is a perfect itme to develop sustainable and reproducible energy storage devices. Recent efforts have focused on more efficient energy storage devices including supercapacitors which have high power densities, fast charge discharge capabilities and long life cycles. Such supercapacitors are aimed at emergency power systems, electric vehicles, and devices where high-power delivery is required and several types of materials, such as metal oxides and conducting polymers have been used for their electrodes. However, most of these materials often suffer from low capacitance and high cost, so in this we attempted to use orange peel, a bio-waste, for electrochemical charge storage applications. Before using orange peels for supercapacitor applications, orange peel was pre-carbonized at 400 oC and followed by chemical activation using KOH to optimize the surface area/porosity of the orange peel. The electrochemical properties of the carbonized orange peel were investigated by cyclic voltammetry (CV) and galvanostatic charge discharge (CD) measurements in alkaline media. 1:1 ratio of carbonized orange peel and KOH showed the most promising results by yielding maximum specific capacitance of 489 F/g in 3 M KOH at a current density of 0.4 A/g. The cyclic voltammetry curves were of rectangular in shape, indicating ideal capacitive behavior. The effect of different electrolytes such as LiOH, NaOH and KOH on electrochemical properties of the carbonized orange peel was also investigated. The results showed almost 100% capacitance retention over 5000 cycles of charge-discharge. These electrodes show no degradation in capacitive properties upon bending, suggesting that it can be used for flexible energy storage devices. We believe that this study provides a facile method to convert bio-waste into a high performance material for applications in the next generation of flexible and cost-effective energy storage devices