Coffee grounds were converted into S-doped activated carbon (SAC) in the presence of an active agent and S dopant through a one-step synthesis approach. Carbonization, activation, and S doping was achieved through this one-step methodology. The SAC was used as an electrode material for the preparation of a symmetric electrical-double-layer capacitor (EDLC), and the influence of the loading mass of the active materials on the capacitive behaviors was investigated. The assembled SAC-based symmetric EDLC not only yielded a high capacitance but it also afforded a satisfactory capacitance retention. The symmetric EDLC constructed with loading mass SAC of 7.5 mg cm-2 was capable of delivering a maximum gravimetric and areal capacitance of 200 F g-1 and 1.5 F cm-2 , respectively. The compatibility of the gravimetric and areal capacitances of SAC was mainly attributed to the high abundance of interconnected pore channels, which were beneficial for the increased contact area between electrode and electrolyte ions, fast charge transfer, and fast diffusion of the electrolyte ions. In addition to the well-developed porous networks, the introduction of S into the carbon frameworks significantly enhanced the electrical conductivity, storage capacity, and rate capability. The developed one-step synthesis provides a facile and effective route for obtaining high-performance capacitive electrode materials and realizing high value-added utilization of biomass.
Keywords: S doping; biomass; capacitors; carbon; porosity.
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