Electrodeposition Coupled with Electrochemical Activation for Constructing High-Capacitance Carbon Quantum Dot-Based Films on Carbon Cloth as Electrodes

Carbon quantum dots (CQDs) have sparked notable research interest in energy storage because of their excellent conductivity, tunable surface chemistry, environmental friendliness, and low production cost. However, the exploration of the intrinsic electrochemical activity of CQDs is very limited and further improvement for the activity of CQDs is still a challenge. Therefore, a scalable CQD-based film was fabricated on N2 plasma-treated carbon cloth (CC) using electrodeposition, which released an areal specific capacitance of 168.8 mF cm–2 and a mass-specific capacitance of 844 F g–1 at 1 mA cm–2 that increased to 572.5 mF cm–2 and 2862 F g–1 after electrochemical activation, respectively. The mechanism analysis revealed that the enhanced capacitance activity of the CQD-based film was mainly attributed to the optimization of edge sites and an increase in graphitized sp2 carbon structures in CQDs as well as the graphene-like structure of the CQD-based film. The solid-state symmetrical supercapacitors assembled using two activated CQD-based films could release a maximum energy density of 17.04 μWh cm–2 and 0.28 mWh cm–3 under a power density of 200 mW cm–2 and 3.33 mW cm–3 and good cycle stability in a PVA/H2SO4 electrolyte. Such a facile strategy used for the fabrication of CQD-based films has broad development prospects for the flexible design of advanced carbon electrodes for energy-storage microdevices.