Bean dregs-based activated carbon/copper ion supercapacitors

Bean dregs-based activated carbon/copper ion redox active electrolytes supercapacitors (BDACCIS) were prepared by combining bean dregs-based activated carbon with copper ion redox active electrolytes, which were prepared by introducing NH4NO3 (NN) auxiliary electrolytes into Cu(NO3)2 (CN) solutions. The physical properties of obtained activated carbon materials are characterized by scanning electron microscopy, powder X-ray diffraction, nitrogen adsorption/desorption isotherm measurements. The electrochemical properties of the constructed supercapacitor are studied by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and cycle life tests. The bean dregs-based activated carbon materials exhibit interestingly well-interconnected porous structure with the large specific surface area of 2905 m2 g−1. As-prepared BDACCIS presents a high specific capacitance (492 F g−1 at 1 A g−1) and high rate performance (285 F g−1 at 20 A g−1). Simultaneously, it also shows the low equivalent series resistance (Rs) and charge-transfer resistance (Rct) of 1.05 and 0.75 Ω, considerable energy and power densities of 51.3 W h kg−1and 855.1 W kg−1, and satisfactory cycling stability with 81.4% capacitance retention after 10000 cycles at 1 A g−1 in 2 M CN + NN redox active electrolyte, demonstrating that the BDACCIS would be a promising supercapacitor.