Graphene papers have great potential for various applications, such as electrodes in energy storage devices, protective coating, and desalination, because of their free-standing structure, flexibility, and chemical tunability. The inner structures of the graphene papers can affect their physical properties and device performance. Here, we investigated a way to fabricate graphene papers from crumpled reduced graphene oxide (rGO) spheres. We found that ultrasonication was useful for tailoring the morphology of the crumpled graphene spheres, resulting in a successful fabrication of graphene papers with tunable inner pore structures. The fabricated graphene papers showed changes in mechanical and electrical properties depending on their pore structures. In addition, the tailored pore structures had an influence on the electrochemical performance of supercapacitors with the fabricated graphene papers as electrode materials. This work demonstrates a facile method to fabricate graphene papers from crumpled rGO powders, as well as a fundamental understanding of the effect of the inner pore structures in mechanical, electrical, and electrochemical characteristics of graphene papers.
Graphene has been extensively investigated as an electrode material for high-performance supercapacitors due to its high electrical conductivity and large surface area. Because conventional graphene-based supercapacitors use reduced graphene oxide (rGO) in a powder form, the particle size can be one of the important factors affecting the supercapacitor performance. In this study, the effect of the particle size of graphene oxide (GO) powders was studied for the electrochemical performance of graphene-based supercapacitors. The GO powders with three different particle size distributions were used for the electrochemical tests after reducing the GO powders using simple microwave irradiation. The chemical characteristics and specific surface areas of the rGO powders synthesized by microwave irradiation (MWrGO) were nearly the same for all cases. However, the supercapacitor using the MWrGO powders with a medium size showed a higher specific capacitance (109.1 F g−1) with a lower internal resistance and efficient charge transfer. This work provides an effective method to enhance the electrochemical performance of the MWrGO powders.
Highly porous activated graphene coated on CVD-graphene/Cu wires enables high-performance wire supercapacitors with enhanced thermal and chemical stability.
Fiber supercapacitors (FSCs) can be used to power future flexible devices such as wearable electronics and smart textiles. Here, highly porous activated graphene (AG) is embedded into graphene fibers to enhance the electrochemical performance of FSCs based on electric double-layer capacitance (EDLC). Wet spinning of AG mixed with graphene oxide (GO) and subsequent chemical reduction of GO to reduced graphene oxide (rGO) enable the fabrication of continuous and conductive graphene fibers. The AG powders with an extremely high surface area significantly improve the electrochemical performance of the FSCs. In particular, the rGO/AG fiber with an rGO/AG mass ratio of 80/20 achieves a specific areal capacitance of 145.1 mF/cm 2 at a current density of 0.8 mA/cm 2 with a PVA/LiCl gel electrolyte. This corresponds to areal energy and power densities of 5.04 μWh/ cm 2 and 0.50 mW/cm 2 for the FSCs, respectively. Furthermore, flexible FSCs using the rGO/AG fibers demonstrate decent cycling capability, with a capacitance retention of 91.5% after 10 000 cycles. This work shows significant potential in fabricating AG-based fibers for developing high-performance flexible FSCs.
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