Waste Coffee Management: Deriving High-Performance Supercapacitors Using Nitrogen-Doped Coffee-Derived Carbon

Abstract

In this work, nitrogen-doped activated carbon was produced from waste coffee powder using a two-step chemical activation process. Nitrogen doping was achieved by treating the coffee powder with melamine, prior to chemical activation. The produced nitrogen-doped carbon resulted in a very high surface area of 1824 m2/g and maintained a high graphitic phase as confirmed by Raman spectroscopy. The elemental composition of the obtained coffee-derived carbon was analyzed using X-ray photoelectron spectroscopy (XPS). The supercapacitor electrodes were fabricated using coffee-waste-derived carbon and analyzed using a three-electrode cell testing system. It was observed that nitrogen-doping improved the electrochemical performance of the carbon and therefore the charge storage capacity. The nitrogen-doped coffee carbon showed a high specific capacitance of 148 F/g at a current density of 0.5 A/g. The symmetrical coin cell device was fabricated using coffee-derived carbon electrodes to analyze its real-time performance. The device showed the highest specific capacitance of 74 F/g at a current density of 1 A/g. The highest energy and power density for the device was calculated to be 12.8 and 6.64 kW/kg, respectively. The stability test of the device resulted in capacitance retention of 97% after 10,000 cycles while maintaining its coulombic efficiency of 100%. These results indicate that the synthesized nitrogen-doped coffee carbon electrode could be used as a high-performance supercapacitor electrode for energy storage applications, and at the same time manage the waste generated by using coffee.