High Performance Pseudocapacitor Electrode Materials Based on CoCl2 Doped Graphene Quantum Dots

This work reports, for the first time, an effective synthesis of CoCl2 doped graphene quantum dots (COCl2-GQDs). Excellent results were obtained by using CoCl2 powder and graphene oxide (GO) as source materials in a facile hydrothermal process. The prepared materials were characterized by using high resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy, U-V Visible spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Powder X-Ray Diffraction (PXRD) and Photoluminescence (PL). HRTEM images suggest that the majority of the CoCl2-GQDs are in the narrow range of 2.5-7 nm in diameter, much smaller than that of GQDs which are approximately 15 nm. By using different excitation energy in PL, the appearance of peak introduces additional energy level between pi and pi*, reinforcing the COCl2 doping process. We observed that CoCl2 electrodes can exhibit a reversible redox reaction of Co2+ <-> Co4+ on the electrode and show specific pseudocapacitance of similar to 300F/g. The new charge storage mechanism by using CoCl2 electrodes are easily scalable and highly economical for future pseudocapacitors which can be extended for a large variety of commercial inorganic salt electrodes.