Waste paper based activated carbon monolith as electrode materials for high performance electric double-layer capacitors

Abstract

A surface modified carbon monolith (m-CM) was successfully synthesized by carbonization of a waste paper precursor, followed by a simple surface modification with a HNO₃ solution. The morphology, pore structure, and surface functional groups of the as-obtained m-CM are characterized by scanning electron microscopy (SEM), N₂ adsorption–desorption measurements, and Fourier transform infrared spectroscopy (FT-IR), respectively. The electrochemical properties are investigated by cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). After surface modification, the surface hydrophilicity and the electrical conductivity of the m-CM is increased by introducing functional groups and dissolution of the impurities, thus the electrochemical performances of the m-CM are significantly improved. A high gravimetric capacitance (C_m) and volumetric capacitance (C_v) of 232 F g⁻¹ and 36.7 F cm⁻³ is obtained at a current density of 5 mA cm⁻² in 2 M KOH electrolyte, respectively. Based on the above investigation, such a treatment could be a promising method to convert organic waste to high-performance carbon electrode materials for electric double-layer capacitors.