Simultaneous Electrochemical Exfoliation and Chemical Functionalization of Graphene for Supercapacitor Electrodes

Abstract

The demand for efficient electrochemical energy storage technology, such as supercapacitors, continues to increase as both the energy and power demands of devices grow. Graphene has attracted wide interest in addressing this energy challenge due to its high conductivity and specific surface area. However, in reality the hydrophobic properties and the restacking of the graphene sheets during device manufacture leads to significantly lower storage performance than that theoretically predicted for isolated sheets. Herein, functionalized graphene was prepared by a convenient one-pot process, where graphene was functionalized with aryl diazonium salts (4nitrobenzenediazonium tetrafluoroborate (NBD) and 4-bromobenzenediazonium tetrafluoroborate (BBD)) simultaneously during oxidative electrochemical exfoliation of graphite. It was found that the specific capacitance for functionalized graphene was significantly improved compared to pristine graphene due to the introduction of pseudocapacitance by the aryl diazonium salts. The dispersibility of functionalized graphene in water was also found to be improved, implying a better hydrophilicity. NBD functionalized graphene which had been exfoliated/functionalized for a total of 30 minutes exhibited the best energy storage properties with a 5 times increase in specific capacitance (17 mF cm-2) compared to pristine graphene (3 mF cm-2).

Self-Assembled 1T-MoS2/Functionalized Graphene Composite Electrodes for Supercapacitor Devices

“…In particular, covalent modification of graphene has been found to be able to control the surface chemistry, porosity, and surface roughness and remains stable under operating conditions . For example, functionalizing graphene with aryl diazonium salts improved the graphene’s dispersibility significantly in aprotic solvent and aqueous solution. , Additionally, supercapacitor electrodes produced from the functionalized graphene possessed a specific capacitance of at least five times higher than the unfunctionalized graphene electrodes due to the redox reactions caused by the functional groups and less restacking. , …”

“…In our previous work, galvanostatic charge/discharge (GCD) measurements have shown that graphene functionalized with 4-nitrobenzenediazonium (NBD) for 30 min exhibited the best electrochemical properties followed by graphene functionalized with 4-bromobenzenediazonium (BBD) for 60 min compared to pristine graphene . The synergistic effect of combining fct-graphene and 1T-MoS 2 greatly enhanced the electrochemical behavior of the coin cells which manifest excellent cyclability (90% capacitance retention after 10 000 cycles) and exceptional capacitance (290 F cm –3 at 0.5 A g –1 ).…”

“…6 For example, functionalizing graphene with aryl diazonium salts improved the graphene's dispersibility significantly in aprotic solvent and aqueous solution. 7,8 Additionally, supercapacitor electrodes produced from the functionalized graphene possessed a specific capacitance of at least five times higher than the unfunctionalized graphene electrodes due to the redox reactions caused by the functional groups and less restacking. 7,9 An alternate approach to overcome the low specific capacitance of graphene is to combine it with conducting polymers or transition-metal dichalcogenide (TMDs) so as to enhance the capacity through frustrated packing.…”

Aryne cycloaddition reaction as a facile and mild modification method for design of electrode materials for high-performance symmetric supercapacitor

“…At the same time, the presence of fluorophenylene moieties allowed to increase the interlayer distance and provide better transport properties for electrolyte ions. The combination of the two factors offers an enhanced capacitance in comparison with more traditional modification methods utilizing diazonium chemistry [47][48][49].…”

Performance Improvement of Supercapacitor Materials with Crushed 3D Structured Graphene

“…10,11 There are various preparation methods of 2D-graphene such as exfoliation and cleavage, chemical vapor deposition (CVD), thermal decomposition, laser-based reduction, chemical, and electrochemical reduction. [12][13][14][15][16][17][18][19][20][21][22] Among them, solution-based reduction of graphene oxide (GO) is a commonly used attractive method for its easy operation in recent years. 8,22,23 Chemically modified graphene (reduced graphene oxide; rGO) are attractive precursors for inexpensiveness and can be applied for producing large scale with a high yield.…”