Coal tar residues-based nanostructured activated carbon/Fe3O4 composite electrode materials for supercapacitors

Oxygen-rich activated carbon with a three-dimensional network structure was prepared by chemical activation of coal tar residues with potassium hydroxide and subsequent carbonization treatment. Nanostructured Fe₃O₄/AC composites were then prepared by simple chemical coprecipitation method and were used as active electrode materials for supercapacitors. The electrochemical behaviors of Fe₃O₄/AC nanocomposites were characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in 1.0 M Na₂SO₃ electrolyte. It was shown that the specific capacitance of Fe₃O₄/AC nanocomposites reached 150 F g^?1 at a current density of 3.0 A g^?1 and was a great improvement over Fe₃O₄ or AC alone. Furthermore, as-prepared Fe₃O₄/AC nanocomposites exhibited long cycle life without obvious capacitance fading even after 1,000 charge/discharge cycles. Compared with pure Fe₃O₄ and AC, the significant enhanced electrochemical performance of Fe₃O₄/AC nanocomposites could be reasonably attributed to the positive synergetic effect between Fe₃O₄ and AC.