Production of novel carbon nanostructures by electrochemical reduction of polychlorinated organic rings under mild conditions for supercapacitors

Abstract

Here, new carbon-based nanostructures were prepared via a one-step electrochemical method using hexagonal and pentagonal polychlorinated organic rings as the carbon source. The electrochemical growth of carbon nanostructures on substrates was accomplished via electrochemical reduction of organic halides in nonaqueous electrolyte solutions containing hexachlorobenzene (HCB), hexachlorocyclopentadiene (HCCP) and mixtures of HCB and HCCP with molar ratios of 2/2, 2/1.2 and 2/0.6. The effect of HCB/HCCP molar ratio, deposition time and temperature on the morphological and structural properties of the carbon coatings was investigated using spectroscopic and microscopic methods. The performance of the carbon nanostructures as supercapacitors was also studied using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in aqueous Na₂SO₄ solutions. The structural and chemical properties of the carbon nanostructures was found to depend strongly on the nature and relative molar ratios of the precursors used in the electrochemical reduction process. In the case of a 2/2 molar ratio of HCB to HCCP, mushroom-like carbon nanostructures are obtained, whereas, higher molar ratios of HCB to HCCP (2/1.2 and 2/0.6) result in carbon nanoflowers with graphitic features. Furthermore, the capacitance measurements show that these novel carbon structures are potential candidates for supercapacitor-based energy storage systems because they offer high specific capacitances (332–73 F g⁻¹ at 0.5 A g⁻¹), good cycling stabilities and a maximum energy density of 16 W h kg⁻¹ at a power density of 250 W kg⁻¹.