Study of the Active Carbon from Used Coffee Grounds as the Active Material for a High-Temperature Stable Supercapacitor with Ionic-Liquid Electrolyte

This study reveals a simple approach to recycle wasted coffee grounds into highly valuable carbon material with superior electrochemical performance. Activated carbon prepared from wasted coffee grounds has been formed via hydrothermal acidic hydrolysis followed by a KOH chemical activation at 800 [Formula: see text]. To understand the electrochemical properties of the sample, a set of characterization tools has been utilized: N(2) and CO(2) adsorption–desorption isotherms, thermal gravimetric analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The specific surface area obtained from a Brunner–Emmett–Teller (BET) analysis reached [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text]. Prepared sample (designated as ACG-800KOH) was tested as electrode material in an electric double layer capacitor (EDLC) device with ionic liquid PYR13-TFSI as an electrolyte. The EDLC test was conducted at temperatures ranging from 20 to 120 [Formula: see text]. The specific material capacitance reached 178 [Formula: see text] [Formula: see text] measured at 20 [Formula: see text] and 50 A [Formula: see text] and was in the range 182 to 285 [Formula: see text] [Formula: see text] at the 20 to 120 [Formula: see text] temperature range.