rGO Electrode Research Articles

Reduced Graphene Oxide As an Advanced Anode for Li-Ion Battery

Although graphite is the most commonly used anode material for Li-ion batteries, its low capacity (372 mAh/g) limits the energy storage performance. Recently, graphene has demonstrated great promise as a candidate to replace graphite due to its high power and high energy densities.1-3 Here, we prepared Li-ion battery anodes based on reduced graphene oxide (rGO) powder obtained from an established company and investigated effects of oxygen contents in the rGO on the energy storage properties. The oxygen content of rGO could be controlled by heat-treating the rGO at 500 oC and 800 oC under Ar condition. The O/C atomic ratios from XPS were 0.208, 0.126, and 0.031 for the pristine rGO, the rGO heat-treated at 500 oC (rGO-HT500) and the 800 oC (rGO-HT800), respectively. We employed Dr. Blade method to prepare the electrodes using the pristine and heat-treated rGO. While the loading density of the electrodes were kept in the range of 1.68−1.75 mgrGO/cm2 electrode, the density gradually decreased with the heat-treatment from 0.62 to 0.21 g/cm3. We then fabricated a Li coin-type cell (CR2032) with the rGO electrode in an Ar-filled glovebox. Li metal foil, Celgard 2500 membrane, and 1 M LiPF6 (in EC/DMC) were used as a counter electrode, a separator, and an electrolyte, respectively. For evaluating energy storage performance of the rGO-based electrode, we conducted galvanostatic charge/discharge test at different current densities in the range of 37.2–3720 mA/g. At the current density of 37.2 mA/g, both electrodes based on the pristine rGO and rGO-HT500 showed ~1000 mAh/grGO, which is greatly enhanced capacity by 2−3 folds relative to the theoretical capacity of graphite (Fig. 1). However, the rGO-HT800-based electrode exhibited only showed a capacity of 579 mAh/grGO, indicating the minor oxygen content could contribute to the charge capacity of rGO in the Li-ion battery. J. Hassoun et al., An advanced lithium-ion battery based on a graphene anode and a lithium iron phosphate cathode. Nano letters 14, 4901-4906 (2014).G. Wang, X. Shen, J. Yao, J. Park, Graphene nanosheets for enhanced lithium storage in lithium ion batteries. Carbon 47, 2049-2053 (2009).F. J. Sonia et al., Understanding the Li-storage in few layers graphene with respect to bulk graphite: experimental, analytical and computational study. Journal of Materials Chemistry A 5, 8662-8679 (2017). Figure 1. (a) Charge/discharge profiles of pristine rGO at difference current densities from 37.5 to 3750 mA/g. (b) Comparison of charge/discharge profiles of pristine and heat-treated rGO electrodes obtained at 37.5 mA/g. Figure 1

Electrochemical characteristics of flexible micro supercapacitors with reduced graphene oxide-carbon nanotubes composite electrodes

In this study, we fabricate solid-state flexible micro-supercapacitors (MSCs) with reduced graphene oxide-carbon nanotube (rGO-CNT) composite electrodes and investigate the electrochemical characteristics by comparing with those of an MSC with rGO electrodes. Regarding the resistance-capacitance time constant and IR drop, the addition of CNTs into the rGO electrodes shows a significant effect owing to both the decrease in the resistance and the increase in the permeability of the electrolytes. Compared to the rGO MSCs, the rGO-CNT MSCs show an excellent areal capacitance of 2.6 mF/cm2, a smaller IR drop of 11 mV, a lower RC time constant of 6 ms, and faster charging/discharging rates with a high scan rate ability up to 100 V/s. The mechanical stability of the flexible rGO-CNT MSCs is verified by 1000 bending cycles. In addition, the electrochemical characteristics of the flexible rGO-CNT MSCs are maintained regardless of the MSC array type.

Rapid and efficient green reduction of graphene oxide for outstanding supercapacitors and dye adsorption applications

Rapid and efficient green synthesis of reduced graphene oxide (rGO) material has been carried out (by the reduction of graphite oxide (GO)) with tulasi (Holy Basil) green tea extract followed by microwave irradiation technique in 1 min. As prepared rGO material shows outstanding multifunctional performance as electrodes for supercapacitors and efficient adsorption of toxic organic dyes from aqueous solutions. The electrochemical performance of rGO electrode for supercapacitor showed that, it exhibits high specific capacitance of 164.6 F g−1 at a current density of 1 A g−1 under aqueous 1 M H2SO4 electrolyte solution, good rate capability (59.6% retention when the current density increases from 1 to 10 A g−1). After 3000 cycles, the attenuation of the specific capacitance is less than 5%, indicating excellent electrochemical stability. Moreover, the maximum adsorption capacity of rGO reaches 416.7 mg/g for malachite green dyes at equilibrium under aqueous solutions.

Vacuum-Assisted Low-Temperature Synthesis of Reduced Graphene Oxide Thin-Film Electrodes for High-Performance Transparent and Flexible All-Solid-State Supercapacitors.

Simple and easily integrated design of flexible and transparent electrode materials affixed to polymer-based substrates hold great promise to have a revolutionary impact on the functionality and performance of energy storage devices for many future consumer electronics. Among these applications are touch sensors, roll-up displays, photovoltaic cells, health monitors, wireless sensors, and wearable communication devices. Here, we report an environmentally friendly, simple, and versatile approach to produce optically transparent and mechanically flexible all-solid-state supercapacitor devices. These supercapacitors were constructed on tin-doped indium oxide coated polyethylene terephthalate substrates by intercalation of a polymer-based gel electrolyte between two reduced graphene oxide (rGO) thin-film electrodes. The rGO electrodes were fabricated simply by drop-casting of graphene oxide (GO) films, followed by a novel low-temperature (≤250 °C) vacuum-assisted annealing approach for the in situ reduction of GO to rGO. A trade-off between the optical transparency and electrochemical performance is determined by the concentration of the GO in the initial dispersion, whereby the highest capacitance (∼650 μF cm-2) occurs at a relatively lower optical transmittance (24%). Notably, the all-solid-state supercapacitors demonstrated excellent mechanical flexibility with a capacity retention rate above 90% under various bending angles and cycles. These attributes underscore the potential of the present approach to provide a path toward the realization of thin-film-based supercapacitors as flexible and transparent energy storage devices for a variety of practical applications.

Relaxing volume stress and promoting active sites in vertically grown 2D layered mesoporous MoS2(1-x)Se2x/rGO composites with enhanced capability and stability for lithium ion batteries

In this paper, an effective strategy to fabricate mesoporous MoS2(1-x)Se2x composites supported on graphene sheets (meso-MoS2(1-x)Se2x/rGO) for use as anode materials for lithium ion batteries (LIBs) is reported. The meso-MoS2(1-x)Se2x/rGO composites possess a two-dimensional (2D) layered structure with well-defined mesoporosity and the MoS2(1-x)Se2x nanoparticles are perpendicularly grown on graphene sheets. Due to the merits of 2D layered structural configuration and sulfur-selenium coupled effect, the meso-MoS2(1-x)Se2x/rGO composites promise the enhanced electrochemical performance for LIBs. Introduction of Se may widen the spacing of the (002) crystal plane, as a result, rendering them more effective diffusion path for both Li+ and e− during the charge and discharge process. More importantly, Se incorporation may further induce the transition of meso-MoS2(1-x)Se2x from 2H phase to more metallic 1 T phase. As such, the meso-MoS1.12Se0.88/rGO electrodes exhibit efficient rate capability and good cycling stability with an optimum capacity of 830 mA h g−1 at a current density of 100 mA g−1 for 150th cycle. The meso-MoS1.12Se0.88/rGO electrode still keeps a capacity of 415.3 mA h g−1 even when the current density is 1000 mA g−1 making them promising for potential practical application. The novel synthetic strategy may be applicable to fabricate a large variety of 2D layered chalcogenide electrode materials for LIBs.

Nano tin dioxide anchored onto carbon nanotube/graphene skeleton as anode material with superior lithium-ion storage capability

As a promising anode candidate for lithium-ion batteries (LIBs), SnO2-based material has been extensively investigated. However, its practical application is still hindered due to the inherent drawbacks of poor conductivity, severe volume expansion, and unavoidable agglomeration of active material during repeated discharge/charge process as well as formation of unstable solid electrolyte interface (SEI) layer. In this paper, the SnO2@carbon nanotube/reduced graphene oxide (SnO2@CNT/RGO) composite is rationally designed and fabricated, in which nano SnO2 nanoparticles (NPs, ~6 nm) are anchored onto three-dimensional (3D) conductive CNTs/RGO skeleton by first assembling SnO2 onto CNT and then entangling SnO2@CNT nanofibers in 3D graphene networks. The synergistic effect of CNT and RGO significantly increase the conductivity and prevent aggregation of active material. In addition, the mesopores structure constructed by CNT and RGO can accommodate the volume change of SnO2 NPs and form more stable SEI layer during repeated discharge/charge process. Therefore, the SnO2@CNT/RGO electrode exhibits not only more stable cycle performance but also more superior rate capacity. The discharge/charge specific capacity at 0.2 A g−1 is 1032/1022 mAh g−1 after 100 cycles. Even at high current density of 2.0 A g−1, it still maintains the discharge/charge capacity of 586/578 mAh g−1 after 200 cycles.

High-performance asymmetrical supercapacitor composed of rGO-enveloped nickel phosphite hollow spheres and N/S co-doped rGO aerogel

An asymmetrical supercapacitor (ASC), comprising reduced graphene oxide (rGO)-encapsulated nickel phosphite hollow microspheres (NPOH-0.5@rGO) as positive electrode, and porous nitrogen/sulfur co-doped rGO aerogel (NS-3D rGO) as negative electrode has been prepared. The NPOH-0.5@rGO electrode combines the advantages of the NPOH hollow microspheres and the conductive rGO layers giving rise to a large specific capacitance, high cycling reversibility, and excellent rate performance. The NS-3D rGO electrode with abundant porosity and active sites promotes electrolyte infiltration and broadens the working voltage range. The ASC (NPOH-0.5@rGO//NS-3D rGO) shows a maximum voltage of up to 1.4 V, outstanding cycling ability (capacitance retention of 95.5% after 10,000 cycles), and excellent rate capability (capacitance retention of 77% as the current density is increased ten times). The ASC can light up an light-emitting diodes (LED) for more than 20 min after charging for 20 s. The fabrication technique and device architecture can be extended to other active oxide and carbon-based materials for next-generation high-performance electrochemical storage devices.

Tailoring properties of reduced graphene oxide by oxygen plasma treatment

We report an easily controllable, eco-friendly method for tailoring the properties of reduced graphene oxide (rGO) by means of oxygen plasma. The effect of oxygen plasma treatment time (1, 5 and 10 min) on the surface properties of rGO was evaluated. Physicochemical characterization using microscopic, spectroscopic and thermal techniques was performed. The results revealed that different oxygen-containing groups (e.g. carboxyl, hydroxyl) were introduced on the rGO surface enhancing its wettability. Furthermore, upon longer treatment time, other functionalities were created (e.g. quinones, lactones). Moreover, external surface of rGO was partially etched resulting in an increase of the material surface area and porosity. Finally, the oxygen plasma-treated rGO electrodes with bilirubin oxidase were tested for oxygen reduction reaction. The study showed that rGO treated for 10 min exhibited twofold higher current density than untreated rGO. The oxygen plasma treatment may improve the enzyme adsorption on rGO electrodes by introduction of oxygen moieties and increasing the porosity.

Tunable Charge Injection via Solution-Processed Reduced Graphene Oxide Electrode for Vertical Schottky Barrier Transistors

We demonstrate, for the first time, the use of a solution-processed reduced graphene oxide (rGO) layer as a work function tunable electrode in vertical Schottky barrier (SB) transistors. The rGO electrodes were deposited by simple spray-coating onto the substrate. The vertical device structure was formed by sandwiching a N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) organic semiconductor between rGO and Al electrodes. By varying the voltage applied to the gate electrode, the work function of rGO and thus the SB formed at the rGO-PTCDI-C8 interface could be effectively modulated. The resulting vertical SB transistors based on rGO-PTCDI-C8 heterostructures exhibited excellent electrical properties, including a maximum current density of 17.9 mA/cm2 and an on–off current ratio >103, which were comparable with the values obtained for the devices based on a CVD-grown graphene electrode. The charge injection properties of the vertical devices were systematically investigated through temperature-depende...

Reduced graphene oxide (rGO): supported NiO, Co3O4 and NiCo2O4 hybrid composite on carbon cloth (CC)—bi-functional electrode/catalyst for energy storage and conversion devices

In the present work, we have synthesized a series of composites with NiO, Co3O4, and NiCo2O4 and reduced graphene oxide (RGO). The hybrid composites were fabricated trough a single step hydrothermal approach with subsequent heat treatment. X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy analyses indicate the metal oxide nanoparticles were integrated well in the carbon cloth substrate with rGO support. The as-prepared materials were evaluated as the electrodes for energy storage and conversion devices. As the electrode for supercapatteries, rGO supported NiCo2O4 exhibits highest specific capacity of 333 C g−1 at a specific current of 1 mA cm−1 when compared to their monometallic oxides and also exhibits excellent cycling stability with 89% retention at 5 mA cm−1 after 5000 cycles in a three-electrode system. Furthermore, we have investigated the electro-oxidation of methanol with these electrode in an alkaline medium. Compared to individual oxide composites, the NiCo2O4–rGO electrode shows excellent electro-catalytic activity towards methanol oxidation with low onset potential of ~ 0.3 V and high catalytic current density. The observed bi-functionality of rGO supported metal oxide composite could be attributed to the enhanced electrical conductivity and the well-integrated contact with carbon cloth back bone. Thereby it can be concluded that the design of hybrid composite electrode could be the better choice of electro-active materials for both energy storage and conversion applications.

Sulfur doped ultra-thin anatase TiO2 nanosheets/graphene nanocomposite for high-performance pseudocapacitive sodium storage

Sodium-ion battery (NIBs) has emerged as a promising low-cost option for large-scale electricity storage applications compared with traditional lithium-ion battery. However, developing anode materials with robust rate capability and long cycle life is even more challenging for sodium-based energy storage devices than lithium-based ones. Here, we report a unique nanocomposite architecture of sulfur doped atomically thin, micro-sized anatase TiO2 nanosheets anchored onto graphene sheets (S-TiO2/rGO). The high surface area of two-dimensional structure, graphene preservation networks and rich Ti3+/oxygen vacancy defects induced by sulfur doping endow S-TiO2/rGO electrode with excellent reversibility and fast kinetics. The electrode delivers a high capacity of 153mAh/g at a rate of 20C (6700mA/g) without evident capacity loss even after 8000 cycles. Further kinetics analysis reveals that the high-rate performance stems from pseudocapacitive process rendered by the 2D-morphology and vacancy-rich TiO2 nanosheets.

Graphene oxide – Ionic liquid composite electrolytes for safe and high-performance supercapacitors

Storage devices have been widely reported to satisfy the increase needs in the electronic and transportation areas. The easy access of the electrolyte ions to the surface of the electrodes of carbon nanomaterials is a challenge to be overcome in supercapacitors, especially in the case of ionic liquid electrolytes. Herein, the study of four different ionic liquids (IL) to select the one that exhibits better electrochemical properties in the presence of GO has been accomplished. Among the prepared IL composites, the one with [SET3][TFSI] showed an increase in the conductivity values and an electrochemical stability of over 3.5 V as measured by linear sweep voltammetry. The viscosity of composite [SET3][TFSI]-GO as a function of different concentrations of GO was discussed considering its effect on the conductivity mechanism. Furthermore, supercapacitors based on neat IL and IL-GO 0.1 wt% with reduced graphene oxide (rGO) were investigated. The best results obtained by cyclic voltammetry of the supercapacitor rGO/[SET3][TFSI]/rGO showed a capacitance value of 95.8 F g−1, whereas the supercapacitor rGO/[SET3][TFSI]-GO/rGO exhibited a capacitance of 125.3 F g−1, both at 5 mV s−1, working in a 2.5 V range; which demonstrates an increase of 31% in capacitance because of the presence of GO in the IL. TEM images indicated that the composite electrolyte increases the compatibility of the ionic liquid electrolyte with the rGO electrode, probably favoring the accessibility of the electrolyte ions to the electrode surface.

3D hierarchical bayberry-like Ni@carbon hollow nanosphere/rGO hybrid as a new interesting electrode material for simultaneous detection of small biomolecules

Metal-organic framework derived hierarchical bayberry-like Ni@carbon hollow nanosphere/reduced graphene oxide (Ni@CHS/rGO) hybrid was synthesized by combining a simple solvothermal reaction with a further annealing treatment. 3D hierarchical bayberry-like Ni@CHS/rGO hybrid not only offered a continuous highly conductive Ni metal and graphene matrix to facilitate the charge transfer, but also allowed uptaking and releasing of electrolytes and enchanted adsorbing of targets due to a hollow structure and introduction of graphene. Consequently, such a charming architecture displays preeminent electrocatalytic activity towards the electro-oxidation on ternary mixtures of ascorbic acid (AA), uric acid (UA) and dopamine (DA). For simultaneous detection of three small molecules, the fabricated sensor exhibited good application prospects toward analytes of DA, UA and AA. Furthermore, three well-separated voltammetry peaks were obtained using Ni@CHS/rGO electrode in differential pulse voltammetry (DPV) measurements. The calibration curves for UA, DA and AA were obtained: 0.25–126µM, 0.25–126µM and 2–4000µM, respectively, the detection limits were 0.05µM, 0.05µM, 0.37µM, respectively. This sensor exhibited excellent sensitivity, good stability, outstanding anti-interference ability and acceptable reproducibility. Moreover, the intriguing sensor was triumphantly applied for the quantitative analysis of UA, DA and AA in human urine and vitamin C tablets samples with satisfactory recovery, which manifests its viability application for practical analysis.

Investigation of super-capacitive nature of reduced graphene oxide nano mesh grown over 18 k gold foil using wings of Parides iphidamas as biological template

This paper deals with the fabrication of novel, reduced graphene oxide nano mesh (rGONM) patterns with longitudinal nano-ridges and transverse nano-ribs using nano tubular structures found on the scales of Parides iphidamas, a butterfly species as biological template. Raman spectra, EDAX and FTIR results confirm the obtained mesh-like morphology that comprises only reduced graphene oxide (rGO). Further, super-capacitor performances of rGO and rGONM-coated gold substrates have been evaluated using cyclic-voltammetry (CV), galvanostatic charge-discharge cycle (GCD) and electrochemical impedance spectroscopic (EIS) analysis. A characteristic rectangular curve obtained from the CV of rGO and rGONM-coated gold electrodes display specific capacitances of 291F/g and 418F/g respectively at a scan rate of 5mV/s. The results obtained from EIS support the superior nature of rGONM-coated electrode against rGO system, suggesting the use of rGONM-Au as a potential candidate for electrochemical super capacitor applications.

Reduced graphene oxide for Pt-free counter electrodes of dye-sensitized solar cells

Here, we report on reduced graphene oxide (rGO) electrode prepared by doctor-blading a viscous rGO paste on FTO substrate followed by sintering at 500°C in argon and its application asa counter electrode (CE) of dye-sensitized solar cells (DSSCs). The paste was prepared by mixing rGO and ethyl cellulose in terpineol. The rGO was prepared from commercially available graphite flakes, which were first oxidized to graphene oxide (GO) by modified Hummers’ process and then the GO was reduced to rGO with hydrazine. Electrochemical analyses – cyclic voltammetry and electrochemical impedance spectroscopy – suggest that the performance of the rGO electrode towards I−/I3− is comparable to that of Pt electrode. Even though the catalytic performance of the rGO film towards the reduction of triiodide was not as good as thermally decomposed Pt electrodes, the overall series resistance of the rGO-based cell was similar to that of the Pt-based cell. When applied to DSSCs asa CE, the rGO electrode performs like a Pt electrode showing the prospect of replacing Pt with a metal-free all-carbon material.

Facile preparation of flower-like NiMn layered double hydroxide/reduced graphene oxide microsphere composite for high-performance asymmetric supercapacitors

NiMn layered double hydroxide (NiMn LDH) and NiMn LDH/reduced graphene oxide (rGO) with flower-like 3D composite were synthesized by a simple solvothermal process. The electrochemical properties of NiMn LDH/rGO composite with different contents of rGO were studied, resulting in enhanced capacitance due to the incorporation of rGO compared with pristine NiMn LDH. The NiMn LDH/rGO composite containing 4.46 wt% rGO (LDH/rGO-4) exhibited the highest specific capacitance of 1500 F g−1 at 1 A g−1 with an excellent cyclic stability of 90.5% over 5000 charging and discharging cycles at 20 A g−1. The asymmetric supercapacitor assembled with LDH/rGO-4 and rGO electrodes exhibited a high specific capacitance of 82.5 F g−1 at 0.5 A g−1 and superior energy density of 29.3 Wh kg−1. These results illustrate that the LDH/rGO-4 composite is a promising material for supercapacitor applications.

A wide potential window aqueous supercapacitor based on LiMn2O4–rGO nanocomposite

Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn2O4/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm2) is 268.75 F/g (258 mF/cm2), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li2SO4 electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.

PW11MO39]5− decorated on Ru-reduced graphene oxide nanosheets, characterizations and application as a high performance storage energy and oxygen reduction reaction

In this report, [PW11MO39]5−@Ru-reduced graphene oxides (rGO) (M: Co, Ni, and Cu) were fabricated using a simple and inexpensive method. Several versatile characterization techniques including spectroscopic and electrochemical methods were used to investigate the nanocomposite. The behavior of the electrocatalysts with respect to supercapacitor application and oxygen reduction reaction (ORR) were investigated in acetic acid solution (pH 4.8) and alkaline media, respectively using voltammetry, galvanostatic charge-discharge and chronoamperometry methods. Results showed that the [PW11MO39]5−@Ru-rGO (M: Co, Ni, and Cu) electrodes towards supercapacitor application have a high specific capacitance (705, 624 and 568Fg−1 for Cu, Co and Ni, respectively), highest energy density of 99.05 relating to power density of 294.93, highest power density of 2400 corresponding to energy density of 28.13 and long life cycling. The ORR on [PW11MO39]5−@Ru-rGO electrodes followed a four-electron transfer reaction at low overpotential. The catalysts exhibited a good catalytic capacity, durability, favorable kinetics, and low price, which make them desirable in conformity to green chemistry requirements.

All-Graphene Oxide Flexible Solid-State Supercapacitors with Enhanced Electrochemical Performance.

The rapid development of flexible and wearable electronics has led to an increase in the demand for flexible supercapacitors with enhanced electrochemical performance. Graphene oxide (GO) and reduced GO (rGO) exhibit several key properties required for supercapacitor components. Although solid-state rGO/GO/rGO supercapacitors with unique structures are promising, their moderate capacitance is inadequate for practical applications. Herein, we report a flexible solid-state rGO/GO/rGO supercapacitor comprising H2SO4-intercalated GO electrolyte/separator and pseudocapacitive rGO electrodes, which demonstrate excellent electrochemical performance. The resulting supercapacitor delivered an areal capacitance of 14.5 mF cm-2, which is among the highest values achieved for any rGO/GO/rGO supercapacitor. High ionic concentration and fast ion conduction in the H2SO4-intercalated GO electrolyte/separator and abundant CH defects, which serve as pseudocapacitive sites on the rGO electrode, were responsible for the high capacitance of this device. The rGO electrode, well separated by the H2SO4 molecular spacer, supplied highly efficient ion transport channels, leading to excellent rate capability. The highly packed rGO electrode and high specific capacitance resulted in a high volumetric energy density (1.24 mWh cm-3) observed in this supercapacitor. The structure, without a clear interface between GO and rGO, provides extremely low resistance and flexibility for devices. Our device operated in air (25 °C 40%) without the use of external electrolytes, conductive additives, and binders. Furthermore, we demonstrate a simple and versatile technique for supercapacitor fabrication by combining photoreduction and electrochemical treatment. These advantages are attractive for developing novel carbon-based energy devices with high device performance and low fabrication costs.

Development of a PrGO-Modified Electrode for Uric Acid Determination in the Presence of Ascorbic Acid by an Electrochemical Technique.

An attractive electrochemical sensor of poly(3,4-ethylenedioxythiophene)/reduced graphene oxide electrode (PrGO) was developed for an electrochemical technique for uric acid (UA) detection in the presence of ascorbic acid (AA). PrGO composite film showed an improved electrocatalytic activity towards UA oxidation in pH 6.0 (0.1 M PBS). The PrGO composite exhibited a high current signal and low charge transfer resistance (Rct) compared to a reduced graphene oxide (rGO) electrode or a bare glassy carbon electrode (GCE). The limit of detection and sensitivity of PrGO for the detection of UA are 0.19 μM (S/N = 3) and 0.01 μA/μM, respectively, in the range of 1–300 μM of UA.