Using Unprofitable Coal to Produce Supercapacitor Electrodes

Abstract

The influence of the porous structure of carbon materials obtained by high-temperature (800–900°С) alkaline activation (with potassium hydroxide) of coal on the electrical capacitance of the resulting electrode materials is investigated in model electrochemical cells. The creation of materials with high electrical capacitance calls for a developed architecture of micropores and mesopores and also a large specific surface that is accessible to the electrolyte ions. Especially with slow potential scanning (up to 40 mV/s), the specific capacitance is greatest for carbon materials based on sapropelic coal (425 F/g for scanning at 2.5 mV/s) and D and T coal (469 and 402 F/g at 2.5 mV/s) with significantly developed pore structure. However, electrode materials based on anthracite, with greater specific surface on account of the higher micropore content, are characterized by lower capacitance (327 F/g at 2.5 mV/s), especially at high scanning speeds (20 F/g at 300 mV/s). For nanostructured electrode composites based on carbonized sapropelic coal filled with Fe–Pt, Co–Pt, and Fe–Pd nanoparticles, the capacitance is 20% higher, on average, than for the initial carbonizate: it is 509 F/g at 10 mV/s for carbonizate filled with Fe–Pd nanoparticles.