Supercapacitor devices for energy storage and capacitive dye removal from aqueous solutions

Abstract

Multiwalled carbon nanotubes (MWCNT) are coated with nitrogen doped activated carbon (NC) for applications in electrochemical supercapacitor electrodes and devices. The capacitive behavior of the electrodes and devices is tested in solutions of organic dyes. The process involves energy accumulation in electrical double layers. The accumulated energy may be further utilized to remove dyes with a similar scheme via discharge of the supercapacitor, also fully regenerating the electrode materials for further use. Proof of concept investigations involve the testing of anionic and cationic dyes and analysis of the influence of dye concentration, charge as well as charge to mass ratio on the capacitance, impedance, specific power and energy of the devices. Cyclic voltammetry and chronopotentiometry data, obtained in different voltage windows, are used for the optimization of device performance. The discussion of quartz crystal microbalance data provides an insight into the factors which govern the charge–discharge behavior. The devices show good cyclic stability. This method offers the advantage of saving energy and applicability to a variety of different dyes.