Application of Rhamnolipids as Dispersing Agents for the Fabrication of Composite MnO2-Carbon Nanotube Electrodes for Supercapacitors

Abstract

The high theoretical capacitance of MnO2 renders it a promising material for the cathodes of asymmetric supercapacitors. The good dispersion of MnO2 and conductive additives in a nanocom-posite electrode is a key factor for efficient electrode performance. This article describes, for the first time, the application of rhamnolipids (RL) as efficient natural biosurfactants for the fabrication of nanocomposite MnO2-carbon nanotube electrodes for supercapacitors. RL act as co-dispersants for MnO2 and carbon nanotubes and facilitate their efficient mixing, which allows for advanced capacitive properties at an active mass of 40 mg cm−2 in Na2SO4 electrolytes. The highest capacitance obtained from the cyclic voltammetry data at a scan rate of 2 mV s−1 is 8.10 F cm−2 (202.6 F g−1). The highest capacitance obtained from the galvanostatic charge–discharge data at a current density of 3 mA cm−2 is 8.65 F cm−2 (216.16 F g−1). The obtained capacitances are higher than the capacitances of MnO2-based electrodes of the same active mass reported in the literature. The approach developed in this investigation is simple compared to other techniques used for the fabrication of electrodes with high active mass. It offers advantages of using a biocompatible RL biosurfactant.