Luminescent MoS2 Quantum Dots with Tunable Operating Potential for Energy-Enhanced Aqueous Supercapacitors

Wide band gap luminescent MoS2 quantum dots (QDs) and MoS2 nanocrystals (NCs) have been synthesized by using laser-assisted chemical vapour deposition and used as an electrode material in supercapacitors. Size-dependent properties of the MoS2 QDs and NCs were examined by UV-vis absorption photoluminescence, and Raman spectroscopy. The morphological evolution of the NCs and QDs were characterized by using field emission scanning electron microscopy, high-resolution ti mission electron microscopy, and atomic force microscopy. The as - synthesized uniform QDs with a size similar to 2 nm of nm exhibited an extended electrochemical potential window of 0.9 V with a specific capacitance value of 255 F/g, while the NCs values were 205 F/g and 0.8 V and the pristine MoS2 with values of 105 F/g and 0.6 V at a scan rate of 1 mV s(-1). A shorter conductive pathway and 3D quantum confinement of MoS2 QDs that exhibited a higher number of active sites ensure that the efficient charge storage kinetics along with the intercalation processes at the available edge sites enable significant widening of operating potential window and enhance the capacitance. The symmetric device constructed with the QDs showed a remarkable device capacitance of 50 F/g at a scan rate of 1 mV s(-1) with an energy density of similar to 5.7 W h kg(-1) and achieved an excellent cycle stability of 10,000 consecutive cycles with similar to 95% capacitance retention.

Automated summary

Wide band gap luminescent MoS2 quantum dots (QDs) showed superior electrochemical performance in supercapacitors compared to MoS2 nanocrystals (NCs), with higher specific capacitance value and wider operating potential window.