Graphene Oxide For Supercapacitors Research Articles

Integration of a Flexible, Stretchable, Environment-Benign, and Highly Conductive PVA/H3PO4 Hydrogel as a Quasi Solid-State Electrolyte in Reduced Graphene Oxide Supercapacitors

Integration of a Flexible, Stretchable, Environment-Benign, and Highly Conductive PVA/H₃PO₄ Hydrogel as a Quasi Solid-State Electrolyte in Reduced Graphene Oxide Supercapacitors

High-performance reduced graphene oxide supercapacitors enabled by simple amino hydroquinone dimethylether.

Reduced graphene oxide (rGO) supercapacitors usually feature poor capacitive characteristics. In the current work, coupling of the simple, nonclassical redox molecule amino hydroquinone dimethylether with rGO was found to boost the rGO capacitance to 523 F g-1. The assembled device exhibited an energy density of 143 Wh kg-1 and excellent rate capability and cyclability.

Ultralong and Millimeter-Thick Graphene Oxide Supercapacitors with High Volumetric Capacitance

The fabrication of a high energy density supercapacitor with electrodes bearing ultrahigh aspect ratio active materials is still a big challenge. Here, we successfully developed ultralong and millimeter-thick supercapacitors, which enable practical applications due to the large electrochemical volumetric capacitance overcoming the limits of previous carbon-based materials. The gel graphene oxide fibers (GOFs) with an ultrahigh aspect ratio of over 20,000,000 were completely reduced at room temperature and biscrolled with a conductive Korean traditional paper used as the matrix material for the supercapacitors without any post-treatment. The average cell capacitance value of the yarn-type supercapacitors containing 80 reduced GOFs is maximized at a scan rate of 100 mV/s. The capacitance measured at a scan rate of 1000 mV/s is over 75% of that measured at 100 mV/s.

Materials and electrode designs of high-performance NiCo2S4/Reduced graphene oxide for supercapacitors

NiCo2S4 is one of the most promising bimetallic sulfides for use in energy-storage systems, but more studies are needed to endow NiCo2S4 with a high electrochemical reaction capability and reversibility. In this work, we present rationally materials design of an optimal NiCo2S4 nanoparticle in a reduced graphene oxide (RGO) matrix as a NiCo2S4/RGO nanocomposite. Furthermore, we report the improvements in the materials technology, demonstrating the NiCo2S4/RGO nanocomposite electrode with an excellent specific capacitance of 963–700 F g−1 at 1–15 A g−1, high capacitance retention of 70%, and long cycle life of 3000 cycles. The practical application is showcased in an asymmetric supercapacitor with a high active-material loading. The NiCo2S4/RGO nanocomposite shows a high energy density of 31 Wh kg−1 at a power density of 987 W kg−1 and maintains an excellent density of 23 Wh kg−1 at a high power density of 7418 W kg−1. The outstanding electrochemical utilization and stability of the NiCo2S4/RGO nanocomposite confirm that our systematic optimization in the materials science and technology in terms of the active-material synthesis, the electrode development, and the device design/fabrication would benefit the future development of high-performance supercapacitors.

Effect of Graphite Precursor Flake Size on Energy Storage Capabilities of Graphene Oxide Supercapacitors

In this research supercapacitors were fabricated using graphene oxide (GO) as the electrode material. GO was synthesized using natural graphite precursor with varying flake sizes. GO was characterized by High-Resolution Transmission Electron Microscopy (HRTEM), Elemental Analysis, Fourier Transform Infrared (FTIR) spectroscopy and Raman spectroscopy. Cyclic voltammetry was carried out at different scan rates to determine the specific capacitance and energy density of the electrode material. An increase in specific capacitance was seen with an increase in graphite precursor flake size. A specific capacitance and energy density of 204.22 F.g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and 102.11 kJ.kg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> respectively at scan rate 10 mV.s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> was obtained for the GO sample synthesized from graphite precursor with an average particle size of 0.45 mm. This sample also had the highest specific capacitance for all scan rates.

Comparing Graphite and Graphene Oxide Supercapacitors with a Constant Potential Model

Electric double-layer capacitors store energy because of the adsorption of ions on the surface of electrodes. A realistic model to describe the electrolyte–electrode interface is based on the const...

Comparative Study of Nanocarbon-Based Flexible Multifunctional Composite Electrodes.

Although nanocarbon-based nanofillers have been widely used to improve the energy-storing and sensing functions of porous materials, the comparison of the effects of different nanocarbon-based fillers on the capacitive and flexible sensing properties of nanocarbon-based porous sponge composite supercapacitor electrodes by combining a carbon nanotube, graphene, and graphene oxide with porous sponge is incomplete. The specific capacitance of carbon nanotube-based electrodes is 20.1 F/g. The specific capacitance of graphene-based electrodes is 26.7 F/g. The specific capacitance of graphene oxide-based electrodes is 78.1 F/g, and the capacity retention rate is 92.99% under 20 000 charge–discharge cycles. Under a bending load of 180°, the capacitance retention rate of graphene oxide sponge composite electrodes is 67.46%, which indicates that the prepared electrodes of supercapacitor have the advantages of high capacitance and good flexibility at the same time. To demonstrate their performance, an array of three graphene oxide supercapacitors in series was constructed, which could light up a red light-emitting diode (LED). The tensile strength of carbon nanotube sponge composite electrodes is 0.267 MPa, and the tensile linearity is 0.0169. The experimental results show that graphene oxide-based sponge composite supercapacitor electrodes have the best capacitance performance and carbon nanotube sponge composites have the most potential as a flexible sensor.

Fabrication and Performance of Self-Supported Flexible Cellulose Nanofibrils/Reduced Graphene Oxide Supercapacitor Electrode Materials.

With the rapid development of portable and wearable electronic devices, self-supporting flexible supercapacitors have attracted much attention, and higher requirements have been put forward for the electrode of the device, that is, it is necessary to have good mechanical properties while satisfying excellent electrochemical performance. In this work, a facile method was invented to obtain excellent self-supported flexible electrode materials with high mechanical properties and outstanding electrochemical performance by combining cellulose nanofibrils (CNFs) and reduced graphene oxide (RGO). We focused on the effect of the ratio of the addition of CNFs and the formation process of the film on the electrochemical and mechanical properties. The results show that the CNFs/RGO12 (where the ratio of CNFs to GO is 1:2) film displayed outstanding comprehensive properties; its tensile strength and conductivity were up to 83 MPa and 202.94 S/m, respectively, and its CA value was as high as 146 mF cm−2 under the current density of 5 mA cm−2. Furthermore, the initial retention rate of the specific capacitance was about 83.7% when recycled 2000 times; moreover, its capacitance did not change much after perpendicular bending 200 times. Therefore, the films prepared by this study have great potential in the field of flexible supercapacitors.

Effective improvement of electrochemical performance of electrodeposited MnO2 and MnO2/reduced graphene oxide supercapacitor materials by alcohol pretreatment

Abstract In this work, basing on the traditional electrodeposition method, we improve the structure and electrochemical performance of MnO2 and MnO2/reduced graphene oxide (MnO2/RGO) electrode materials by alcohol infiltrated substrate process that introduces ethanol oxidation reaction on nickel foam substrate surface. After alcohol treatment, the deposited MnO2 on substrate obtains more uniform thickness and looser distribution, RGO obtains larger deposition area with compact distribution. In addition, the capacity, rate, specific energy, specific power and cycle performance have been greatly improved. MnO2 electrode shows the specific capacitance increasing from 153 and 103 F g − 1 to 270 and 190 F g − 1 at the current densities of 1 and 5 A g − 1, respectively. MnO2/RGO electrode shows specific capacitance increasing from 343 to 254 F g − 1 to 467 and 307 F g − 1 at 1 and 5 A g − 1, respectively. Moreover, the specific capacitance of MnO2 and MnO2/RGO electrodes keep 83.9% and 93.1% retention after 2500 cycles at the large current density of 5 A g − 1, respectively. Based on some scientific universals, we look forward to the proposed alcohol infiltrated substrate process for this work, which may be favorable for the performance enhancement of a series of MnO2-based supercapacitor materials, not only for MnO2 and MnO2/RGO.

Tremella-like NiAl-Layered double hydroxides anchored on polydopamine/reduced graphene oxide for supercapacitor with high energy density

The NiAl-layered double hydroxides (NiAl LDHs) has been known as a very desirable positive electrode material for alkaline supercapacitors due to it can provide a higher theoretical specific capacity than β-Ni(OH)2. However, NiAl LDHs is structurally unstable in an alkaline solution and can easily convert into another crystal (β-Ni(OH)2). Therefore, it is important to study and design the true active phase of the effective electrode material. In this work, we use high-valence Al ions to replace some of the Ni ions in the raw materials to stabilize its crystal structure and prepare the tremella-like NiAl LDHs decorated on polydopamine/reduced graphene oxide (NiAl LDHs@PDA/rGO) by a simple hydrothermal method. The NiAl LDHs@PDA/rGO exhibit high specific capacitance of 2210.7 F g−1 at 1 A g−1 and excellence rate performance (71% of capacitance retention with the increase of current density from 1 to 40 A g−1) as the cathode material for supercapacitor. Furthermore, the hybrid supercapacitor delivers a superior energy density of 58.93 W h Kg−1 at 800.21 W kg−1 and long cycling life. This work not only provides a simple method to prepare the tremella-like NiAl LDHs@PDA/rGO but also paves the way for the development of advanced cathode materials for the next generation of supercapacitors.

Structural reduced graphene oxide supercapacitors mechanically enhanced with tannic acid

Noncovalent bonding of graphene/aramid nanofiber electrodes with tannic acid leads to enhanced mechanical properties while maintaining good energy storage.

Flexible reduced graphene oxide supercapacitors processed using atmospheric-pressure plasma jet under various temperatures adjusted by flow rate and jet-substrate distance

We vary the substrate temperature by adjusting the nitrogen flow rate and jet-substrate distance during nitrogen atmospheric-pressure plasma jet (APPJ) processing of screen-printed reduced graphene oxides (rGOs) on carbon cloth. The APPJ-processed rGOs on carbon cloth are then used as electrodes for supercapacitors. Increasing the nitrogen flow rate could reduce the gas temperature and enhance the reactivity of the reactive plasma species. Typically, lowering the temperature slows down the chemical reaction; however, increased reactivity of the reactive plasma species at the same jet-substrate distance could compensate the temperature effect. A nitrogen APPJ could improve the wettability of the screen-printed rGOs on carbon cloth. We found that 20-s APPJ treatment increases the areal capacitance from 6.2 mF cm−2 (without APPJ treatment) to 22.4 mF cm−2 (700 °C, 30 slm), as evaluated by galvanostatic charging/discharging (GCD) measurements under a constant current of 0.25 mA. Further, 20-s nitrogen APPJ processing at temperatures of ∼600 °C–700 °C could obtain the best areal capacitance value. The capacitance value of the fabricated flexible rGO supercapacitor remains at similar level after 1000-cycle mechanical bending test with a bending radius of 5 mm.

Highly Multifunctional Dopamine-Functionalized Reduced Graphene Oxide Supercapacitors

Summary Batteries and supercapacitors that possess the mechanical properties of structural composites are desirable for electric vehicles and aerospace applications, as energy may be stored within structural panels to realize significant mass and volume savings. However, current electrode materials suffer from poor mechanical performance, as described by a low multifunctional efficiency parameter (

Effects of proton irradiation on graphene-based supercapacitors

Supercapacitors have potential for use in space applications. To support their use in this area, the durability of the component materials and the device performances in the space environment need to be investigated. This work investigated the effects of proton irradiations on graphene oxide (GO) and reduced graphene oxide (RGO) materials and supercapacitor electrodes containing them. The results indicated that RGO-based supercapacitor electrodes could maintain their electronic performance after proton irradiation, whereas the GO-based supercapacitor electrodes could not maintain their electronic performance after proton irradiation. The changes in the material properties of GO and RGO due to proton irradiation are also presented, which provide evidences for the changes in the performance of the supercapacitors. Our results may foster the use of graphene-based supercapacitors for space applications.

Differential Capacitance and Energetics of the Electrical Double Layer of Graphene Oxide Supercapacitors: Impact of the Oxidation Degree

Graphene oxide (GO)-based materials have been considered for potential energy storage applications, in particular supercapacitors. Here, for the first time, we present a detailed analysis of the properties of GO-based supercapacitors as a function of both chemical composition and charge density on the electrodes. Differential capacitance was determined and the effect of the degree of oxidation of the electrodes was taken into account. Also, structural and energetic details on the electrode–electrolyte interaction and, consequently, the double-layer electric structure were analyzed. The differential capacitance value for all supercapacitors is within the range of 1.5–5.4 μF cm–2 in the ±3 V window for the electrode potential and presents the highest value for the R20 system, which also had the highest mean integral capacitance. One important result is the gradual transition from bell-shaped to camel-shaped as the degree of oxidation increases. The results presented here provide the missing complement for a...

Performance stability of solid-state polypyrrole-reduced graphene oxide-modified carbon bundle fiber for supercapacitor application

The stability performance of a solid-state polypyrrole-reduced graphene oxide (PPy-rGO) supercapacitor electrode after a series of charging-discharging cycles is investigated. The electrochemical performances show that the capacity retention, specific capacitance, equivalent series resistance, and charge transfer resistance all decrease after charging-discharging cycles. Thermogravimetric analysis shows the degradation of electroactive materials, causing decreased electrochemical performance of PPy-rGO. The morphology changes reveal that the pore size is reduced by ∼12 μm at the 1000th charge-discharge cycle, which limits the diffusion of electrolyte ions into the electrode. The positive shifts in the binding energy of the N1s spectra at the 500th and 1000th charge-discharge cycles indicate the formation of a hydrogen-bridge bond, affecting the electron transfer in the PPy-rGO composite as observed through X-ray photoelectron spectroscopy. Moreover, the structural properties of rGO change from amorphous to graphitic after a series of charging-discharging processes, as shown by the Raman spectra. Furthermore, the peak of the NH bending vibration is red-shifted by approximately 108 cm−1, indicating the changes in the chemical environment after a series of charging-discharging cycles, as shown by Fourier transform infrared spectroscopy.

Layered Assembly of Reduced Graphene Oxide and Vanadium Oxide Heterostructure Supercapacitor Electrodes with Larger Surface Area for Efficient Energy-Storage Performance

The architecture of a supercapacitor (SC) electrode plays a crucial role in defining the overall energy-storage performance of the SC. Layer-by-layer assembly of a reduced graphene oxide (rGO) and vanadium oxide (V2O5) (rGO/V2O5)-based heterostructure is patterned in interdigitated electrodes (IDEs) deposited directly on a flexible conducting current collector for the SC. The IDE pattern offers efficient accessibility to the electrolyte ions and a synergistic contribution for energy storage. An as-fabricated solid-state flexible sandwich-type SC with IDEs displays a more efficient energy-storage performance than a conventional solid-state flexible sandwich-type SC composed of rGO/V2O5 electrodes. Moreover, a solid-state flexible in-plane microsupercapacitor (MSC) is fabricated, which offers much higher capacitance (24 mF/cm2 and 34.28 F/cm3) and energy density (3.3 μWh/cm2 and 4.7 mWh/cm3). The as-fabricated flexible in-plane MSC displays a negligible capacitance loss of about 6.3% after 10 000 charge–dis...

Sequential entrapping of Li and S in a conductivity cage of N-doped reduced graphene oxide supercapacitor derived from silk cocoon: a hybrid Li–S-silk supercapacitor

Li and S compounds are currently exploited for their applications in battery industry. Here, we discovered that Li–S compounds exhibit supercapacitor like properties in a context-dependent manner viz., when Li and S atoms are entrapped in a conductivity cage of N-doped reduced graphene oxide (ND–RGO) supercapacitor derived from silk cocoon, it resulted in the formation of a superior hybrid Li–S-silk (ND–RGO–Li–S) supercapacitor. Interestingly, ND–RGO–Li–S proves to be a better supercapacitor than ND–RGO alone. Electrochemical properties of ND–RGO versus ND–RGO–Li–S indicated that the later has higher capacitance (~ 10.72%), lower resistance (~ 2.98%), and higher time constant or relaxation time (~ 7.52%). Thus, in one of the first attempts, caging Li and S in ND–RGO supercapacitor matrix offers a new role for Li–S, as an improved supercapacitor, unlike its current application as a battery.

Fabrication of Graphene Oxide Supercapacitor Devices

The fabrication, characterization, and energy storage capacity of a graphene-oxide (GO)-based supercapacitor device is reported. This device is fabricated via a facile screen-printing technique, providing a highly reproducible and flexible symmetrical supercapacitor device. The capacitive properties of these GO devices are investigated in both aqueous electrolytes and room temperature ionic liquids. The GO devices are shown to improve the capacitive performance from 0.82 F g–1 displayed by a graphitic screen, to a competitive 423 F g–1, representing a ca. 500-fold increase. The GO supercapacitor device also exhibits an impressive power handling capability of up to 13.9 kW kg–1 and an energy density of 11.6 Wh kg–1. This work demonstrates that GO, before it has been reduced to graphene, is a high performance supercapacitor material of its own right.

The Influence of the Interlayer Distance on the Performance of Thermally Reduced Graphene Oxide Supercapacitors.

In this paper, cationic surfactant cetyltrimethylammonium bromide (CTAB) was employed to prevent the restack of the thermally reduce graphene oxide (TRG) sheets. A facile approach was demonstrated to effectively enlarge the interlayer distance of the TRG sheets through the ionic interaction between the intercalated CTAB and ionic liquids (ILs). The morphology of the composites and the interaction between the intercalated ionic species were systematically characterized by SEM, SAXS, XRD, TGA, and FTIR. In addition, the performance of the EDLC cells based on these TRG composites was evaluated. It was found that due to the increased interlayer distance (0.41 nm to 2.51 nm) that enlarges the accessible surface area for the IL electrolyte, the energy density of the cell can be significantly improved (23.1 Wh/kg to 62.5 Wh/kg).