Cocoa husk as precursor of carbonaceous materials for supercapacitors electrodes

Abstract

Activated carbon materials are widely used as high-performance electrodes for supercapacitors because they allow improving the electrochemical performance of these devices. The development of high surface areas and high porosity contributes to the energy storage by double electric layer, whereas the content of different functional groups on their surface to the pseudocapacitive storage. In addition, they can be obtained from lignocellulosic wastes providing a novel and economic perspective for the development of carbon-based electrodes. In this work, activated carbons were synthesized from cocoa husks using KOH as activating agent. The materials were obtained at three impregnation ratios (1:1, 3:1, 5:1) and three carbonization temperatures (500, 650, and 800 °C), optimizing the best conditions to obtain materials with high surface areas and porosity together with surface functional groups to improve energy storage. The results show that the 800 °C synthesized material with 3:1 impregnation ratio presents a capacitance of 120 F/g at 1 A/g, with a retention capacity of 93 % after 12,000 cycles, being the best electrochemical behavior among the carbons prepared. This is attributed to the adequate micro-mesoporosity, content of surface oxygenated functional groups and high surface area (1444 m2/g).