Waste coffee grounds derived nanoporous carbon incorporated with carbon nanotubes composites for electrochemical double-layer capacitors in organic electrolyte

Abstract

Carbon nanotube (CNT)-incorporated nanoporous carbon (NPC) derived from the waste coffee ground composite was proposed as a potential electrode material for electrochemical double layer supercapacitors with an organic electrolyte. CNT-incorporated NPC pastes with different CNT contents were fabricated via a simple ball-milling method and then coated on a carbon nanofiber paper using a doctor blade technique. According to structural characterization data, the 3%CNT/NPC material offered a high specific surface area of 1157.8 m2 g−1 with a small average pore diameter of 1.42 nm owing to the intercalation of CNT structures between the NPC flakes. From electrochemical measurements, a coin cell using 3%CNT/NPC in 1 M TEABF4/ACN exhibited a high specific capacitance of 132 Fg−1 and a high specific energy of 37.7 Wh kg−1 at 0.5 Ag−1, which are considerably higher than those using NPC (74 Fg−1 and 20.1 Wh kg−1) and CNT (48 Fg−1 and 14.7 Wh kg−1). In addition, the composite possessed higher rate capability, better cycling stability, and lower self-discharge rate compared with NPC and CNT electrodes. Hence, the 3%CNT/NPC composite was promising as an active material for producing advanced supercapacitors. © 2021 Elsevier Ltd