The use of activated carbon from coffee endocarp for the manufacture of supercapacitors

Abstract

Activated carbon (AC) was obtained from the dry endocarp of coffee for the manufacture of electrodes for supercapacitors. Four different AC samples were prepared via chemical methods at different proportions of impregnation (Xp) and two temperatures of activation (600 and 700 °C). Scanning Electron Microscopy technology and the measurement of the adsorption of N2 via the Brunauer–Emmett–Teller (BET) method were used to identify the morphological characteristics of AC, revealing high surface areas. Energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy techniques were applied for chemical composition analysis, identifying oxygenated functional groups which contribute to the increase in capacitance. The supercapacitor comprised two electrodes mounted on a tantalum cell, which was electrochemically evaluated by means of cyclic voltammetry and galvanostatic chronopotentiometry charge/discharge measurements. The maximum specific capacitance encountered was 186 Fg−1, which was obtained from the AC sample with a surface area of 734 m2g−1 and prepared at an Xp of 150% and an activation temperature of 700 °C. All AC samples exhibited good electrochemical performance.