Coffee-derived activated carbon from second biowaste for supercapacitor applications

The electrochemical energy storage performance of activated carbons (ACs) obtained from coffee-derived biowastes was assessed. ACs were obtained from spent coffee ground second waste, after polyphenol extraction, by means of a hydrothermal process followed by physical or chemical activation. The resulting materials exhibited microporous structures with a total specific area between 585 and 2330 m(2).g(-1). Scanning electron microscopy (SEM) revealed a highly porous microstructure in the case of the chemically activated carbons, while physical activation led to a cracked micro-sized morphology. The electrochemical properties of the materials for supercapacitor applications were investigated in 1 M Na2SO4. After chemical activation, the coffee-derived material displayed a capacitance of 84 F.g(-1) at 1 A.g(-1) in a 1.9 V voltage window, with 70% capacitance retention at 10 A.g(-1) and 85% retention after 5000 cycles of continuous charge-discharge. This work demonstrates how coffee secondary biowaste can be conveniently activated to perform as electrochemical energy storage material, contributing to its revalorization and reinsertion in a circular economy. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The electrochemical energy storage performance of activated carbons derived from coffee biowastes were evaluated, showing promising potential for supercapacitor applications.