Improvement of Mesoporosity on Supercapacitive Performance of Activated Carbons Derived From Coffee Grounds

• Published in: Bulletin of the Korean Chemical Society 2021, 42(5), , pp.748-755
• Main Authors: Lee, Ui‐Won, Yang, Guijun, Park, Soo‐Jin
• Format: Article
• Language: English
• Subjects: KOH activation; Porous carbons; Supercapacitor; Waste coffee grounds; 화학
• ISSN: 1229-5949; 0253-2964; 1229-5949
• DOI: 10.1002/bkcs.12251

Activated carbons with different porosities derived from coffee, which prepared by the potassium hydroxide (KOH) activation method, are used as electrode for supercapacitors. The prepared materials indicated a well‐designed porous structure that provides countless adsorption sites, leading to high supercapacitor performance. Mesopores allow rapid diffusion of electrolyte ions, while micropores usually provide abundant adsorption sites for ions. Therefore, appropriate control over pore‐size distributions is a key factor for good electrochemical performance. The porosity and surface structure of activated coffee grounds (ACGs) are highly dependent on both the activation temperature and KOH/carbonized materials weight ratio. The ACGs were characterized using N2 adsorption at 77 K. The specific surface area increased from 1.75 to 3065 m2/g. Cyclic voltammetry and galvanostatic charge–discharge tests were employed in the evaluation of the electrochemical behavior of each sample. The ACG materials have a high specific capacitance of 127.8 F/g and cycle stability after 2500 cycles. The waste coffee grounds were used as carbon precursors. Carbonization was carried out at 600°C under N2 flow, then activated carbon derived from carbonized coffee grounds at 900°C with various KOH weight ratio. The prepared porous activated carbon were used as electrode for supercapacitors. The porosity of electrode provides ion adsorption sites, leading to high electrical capacitance. The different size of pores work as different roles. Micropores store electrical energy by trap electrolyte ions, while mesopores store the electrolyte ion and form a channel for ion rapid diffusion pathways for the power delivery. Therefore, proper pore‐size distribution control is one of key factor for good electrochemical performance.