Fast Response Electrochemical Capacitor Electrodes Created by Laser-Reduction of Carbon Nanodots

The conversion of small bio-based molecules into electro-active functional carbon nanomaterials such as carbon nanodots or graphene is attracting increasing interest. In this communication we demonstrate the use of laser-reduced carbon nanodots (lrCND) as electrodes for electrochemical capacitors. A CO2-laser-assisted process is utilized to convert CNDs into highly conductive 3D-carbon monoliths. Exclusion of molecular oxygen from the reaction environment has a positive effect on device parameters and particularly on the frequency response. Using this simple and inexpensive method, an extremely fast RC time constant of 0.29 ms and a capacitance of 0.259 mF cm−2 at 120 Hz were obtained. This can be attributed to an effective conversion of CNDs into graphitic carbon in an oxygen-free environment and the presence of unconverted CNDs in the 3D-carbon network acting as doping agents.