Experimental and Theoretical Findings of the Concerted Effect of Dual Quantum Dots on a Graphene Matrix for Energy Storage Applications

Abstract

The construction of composite electrode materials that exhibit superior energy and power densities has stirred rigorous research on supercapacitors. Herein, we have successfully designed nitrogen-doped carbon dots (CDs) and hematite dots (HtDs) functionalized reduced graphene (RG) hybrid ternary composites (RG@CDs/HtDs) by liquid exfoliation followed by the solvothermal method. The hybrid electrode material, RG@ CDs/HtDs, exhibits a high specific capacitance of 1566 F/g at a scan rate of 2 mV s −1 and excellent stability up to 10,000 cycles. The DFT calculations have been performed to investigate the capacitance enhancement in the hybrid structure. The enhanced quantum capacitance and intense electronic states near the Fermi level for the ternary structure RG@CDs/HtDs justify the superior charge storage. When HtDs and CDs are introduced into RG, charge transfers from the Fe 3d orbital to the C 2p orbital of RG occur. An asymmetric aqueous supercapacitor device has been fabricated using RG@CDs/HtDs as a cathode and Mn 3 O 4 /C as an anode. Remarkably, the assembled aqueous asymmetric supercapacitor operates in a stable and wide potential window of 2.5 V with an ultrahigh energy density (134 Wh kg −1 ) along with extraordinary rate capability and is stable at 10,000 cycles performance that was validated on powering of the red light-emitting diode (LED).

Imine-Linked π-Conjugated Covalent Organic Frameworks as an Efficient Electrode Material for Pseudocapacitive Energy Storage

“…The charge storage properties depend on both the surface-capacitive and diffusion-controlled processes. Equation shows a power law, which represents the correlation between the scan rate and current from CV. , I = a ν b where I is the peak current, ν is the scan rate, and a and b are constants in this equation. The b value can be derived from the slope of the log[ i ] vs log[ν] plot, which represents the degree of diffusion control and surface-capacitive process, shown in Figure S9a.…”

Metal–organic framework and graphene composites: advanced materials for electrochemical supercapacitor applications

“…Also, the synergistic as well as annealing effect of various metals are the driving forces to enhance the electrochemical performance towards supercapacitor applications. 186–188 In the electrochemical examination, the added crystal water supports a stable structure and inhibits the dissolution of manganese oxide. Second, K 0.5 Mn 2 O 4 nanosheets with a vertical orientation and an interlayer spacing of 7.2 Å offer a large number of places for the storage of electrolyte ions and improve the efficiency of electrolyte uptake on the electrochemical interface.…”