Graphene Oxide Composite Electrode Research Articles

Electrochemical Determination of Bisphenol A in Saliva by a Novel Three-Dimensional (3D) Printed Gold-Reduced Graphene Oxide (rGO) Composite Paste Electrode

A novel synthesized gold (Au)-reduced graphene oxide composite (rGO) was used for the fabrication of an electroactive paste inserted in a three-dimensional (3D)-printed platform for the determination of bisphenol A (BPA). The proposed method exhibits good response towards oxidation of BPA in the linear concentration range from 1.00 × 10−7 mol L−1 to 1.00 × 10−2 mol L−1. The Au-rGO based 3D-printed platform determined BPA with a detection limit of 3.52 × 10−9 mol L−1, in comparison with rGO based 3D-printed platform, where the limit of detection was 3.05 × 10−6 mol L−1. Gold modification of rGO improves the sensitivity and electrochemical behavior of the material for BPA oxidation. The method was validated using five saliva samples collected from children.

High-efficiency layered sulfur-doped reduced graphene oxide and carbon nanotube composite counter electrode for quantum dot sensitized solar cells

A high-efficiency layered sulfur-doped reduced graphene oxide and carbon nanotube composite counter electrode for quantum dot sensitized solar cells is prepared via ultrasonic dispersion followed with simultaneous reduction and doping by hydrothermal using Na2S as a reductant and sulfur source. Scanning and Transmission electron microscopy show the layered composite with carbon nanotube-bridges between reduced graphene sheets. An increase in sp2C/sp3C ratio of composite is revealed for the first time by the analysis of X-ray photoelectron spectra. Electrochemical tests show that the charge transfer resistance is 1.76Ω. The power conversion efficiency of 5.70% is obtained for the quantum dot sensitized solar cell based the composite counter electrode, and is 18.26%, 76.47%, and 126.19% higher than those of unsulfured composite, reduced graphene, and carbon nanotube counter electrodes, respectively. This is mainly due to the improvement of morphological and property of sulfur-doped reduced graphene and carbon nanotube composite, which presents a high specific surface area, high conductivity, providing abundant catalytic active sites and fast electron transport channels for Sn2− reduction.

Electrical Resistance Response of Reduced Graphene Oxide - Aramid Nanofiber Films to Bending-Induced Strain

Structural energy storage is a field associated with the combination of important functions such as structural reliability, energy storage, and energy delivery. The combination of said functions ensures savings in the overall volume and mass of the system. Reduced graphene oxide (rGO) and aramid nanofibers (ANF) composite film electrodes were developed for the purpose of structural energy storage. Graphene is studied due to its remarkable mechanical properties, electrical conductivity and electrochemical surface area. Furthermore, Kevlar® aramid nanofibers enhance the structural properties of the composite due to their excellent mechanical properties. However, external strains are expected on the composite film due to its structural function, and the response of the electrical properties to external strain needs to be evaluated. In this work, the change in electrical resistance was measured under bending-induced strain, using a home-built instrument that allows for accurate strain measurements using image analysis. We show that the resistance of the film decreases under bending via a mechanism we called “mechanical annealing.” This mechanism may be the effect of improved stacking of rGO sheets. The degree of mechanical annealing was also correlated to the amount of bending strain, as well as the amount of ANF loading. Our results demonstrate an improvement, rather than deterioration of the electrical resistance of rGO/ANF composite films under strain, making them suitable for structural energy storage applications.

Cu2+-1,10-phenanthroline-5,6-dione@electrochemically reduced graphene oxide modified electrode for the electrocatalytic determination of L-cysteine

The Cu2+-1,10-phenanthroline-5,6-dione@electrochemically reduced graphene oxide (Cu2+-phen-dione@ERGO) composite electrodes were prepared by the electrochemical immobilization of 1,10-phenanthroline on the ERGO modified glassy carbon electrode (ERGO/GC) for the electrocatalytic determination of L-cysteine (CySH). The as-fabricated Cu2+-phen-dione@ERGO/GC electrode was characterized by field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The electrocatalytic redox behavior of CySH on the Cu2+-phen-dione@ERGO/GC electrode was investigated in phosphate buffer solution by cyclic voltammetry (CV) and amperometry studies. The results indicate that the Cu2+-phen-dione@ERGO/GC modified electrodes exhibit enhanced electrocatalytic peak currents. The double electrocatalytic redox probe at the same operating potential demonstrated excellent electrocatalytic activity towards CySH. The Cu2+-phen-dione@ERGO/GC electrode demonstrated wide concentration range detection from 10.0 to 32,344.0 μM (sensitivity of 0.0009 μA μM−1) and low detection limit (S/N = 3) of 2.0 μM. The as-fabricated CySH sensor electrode has good interference tolerance ability with ascorbic acid, uric acid, sodium nitride, homocysteine, fructose, glucose, glutathione, and alanine. Also, the proposed electrode has been successfully applied to the real-time determination of CySH in human urine sample without any sample pretreatment with the analytical recoveries ranging from 97.8% to 99.5%.

Sulphur-linked graphitic and graphene oxide platelet-based electrodes for electrochemical double layer capacitors

This study presents novel investigations of sulphur-graphitic nanoplatelet (S-GNP) and sulphur-microwave expanded graphene oxide (S-MWGO) composite electrodes for structural electrochemical double layer capacitors (EDLCs) with liquid organic electrolyte 1 M TEABF4 (tetraethylammonium tetrafluoroborate) in propylene carbonate (PC). Elucidating the chemical structure of these electrodes, XPS (X-ray photoelectron spectroscopy) and Raman spectroscopy indicated the presence of CSSC links while mixed EDX (energy dispersive X-ray spectroscopy) elemental maps displayed elemental S outlining the edges of nanoplatelets, concluding the presence of S-links between nanoplatelets. While S-linking improved the mechanical properties and ensured structural integrity of the produced monoliths without the need of any binder, it also decreased the specific surface area of the resulting materials. Furthermore, additional sulphur might have been trapped in other forms, amounting to up to 26 wt% sulphur in the composite graphitic and graphene oxide-based electrodes. Three-point bend testing yielded that an S-GNP-MWCNT monolith with 20 wt% S and 0.24 wt% MWCNT exhibited similar mechanical properties to those of a rigid polyurethane foam. The same S-GNP-MWCNT monolith exhibited an average electrode capacitance of 12.2 F g−1 during discharge at 2.2 mA/cm2. An S-MWGO-MWCNT monolith electrode with 9.6 wt% S, 16.4 wt% carbon black and 0.24 wt% MWCNT exhibited an average electrode capacitance of 64.9 F g−1 during discharge at 2.2 mA/cm2 but higher resistance than the S-GNP electrodes.

Self-supporting lithium titanate nanorod/carbon nanotube/reduced graphene oxide flexible electrode for high performance hybrid lithium-ion capacitor

A Li4Ti5O12 nanorod/carbon nanotube/reduced graphene oxide self-supporting and flexible composite film is prepared through a facile vacuum filtration approach. The Li4Ti5O12 nanorod/carbon nanotube/reduced graphene oxide composite film electrode is able to deliver a reversible specific capacity of 207 mAh g−1, and retains a capacity retention of 90% after 1000 cycles at the current density of 0.35 A g−1. Moreover, a hybrid lithium ion capacitor consisting of an active carbon/carbon nanotube/reduced graphene oxide composite film cathode and the as-prepared Li4Ti5O12 nanorod/carbon nanotube/reduced graphene oxide composite film anode presents high energy density of 67 Wh kg−1 and power density of 1589 W kg−1, respectively. The hierarchically structured Li4Ti5O12 nanorod/carbon nanotube/reduced graphene oxide composite film electrode is lightweight, flexible, conductive additive/binder free, which is a highly desirable feature for wide applications in the wearable energy storage devices.

Biomass waste-carbon/reduced graphene oxide composite electrodes for enhanced supercapacitors

We present a simple and effective alternative which optimizes electrodes based on low-cost carbons for high-performance supercapacitors. The combination with reduced graphene oxide (rGO) greatly improves the operation of microporous carbons easily produced by one-pot activation of grape seeds. The use of composite electrodes with rGO lowers the supercapacitor resistance and enables a much higher rate capability.The mixture of rGO flakes and particles of a highly porous carbon obtained by KOH activation allows retaining the high capacitance of 260 F g−1 of the standard electrodes at 1 mA cm−2 in aqueous H2SO4 whereas the value at 200 mA cm−2 is increased by around 2.4 times. Consequently, at high current density, the capacitor assembled with these composites stores eight times more energy and the power density is multiplied by four.The synergy between rGO and an ultramicroporous carbon produced by CO2-activation results extremely profitable, the cell assembled with composite electrodes reaching three times more energy and power at 200 mA cm−2 than the best performance of the standard counterpart.More importantly, the higher density of the composite electrodes leads to a capacitance of around 200 F cm−3 which translates into a remarkable improvement in the supercapacitor operation normalized to volume.

Fast Determination of Main Bioamines and Precursor Amino Acids in Beer by Miniaturized Electrophoresis Using Gold Nanoparticle Composite Electrode

A gold nanoparticle/reduced graphene oxide composite electrode (AuNP/rGO) was fabricated for the determination of the main bioamines and their precursor amino acids in beer based on a miniaturized capillary electrophoresis with amperometric detection system (mini-CE-AD). The surface morphology and structure of the synthetic AuNP/rGO material were observed by scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction, and Fourier transform infrared spectroscopy. The analytical performance of the composite electrode was verified by cyclic voltammetry and mini-CE-AD approaches. Four target analytes were separated within 7 min in 50 mM Na2B4O7-NaOH buffer (pH 9.35) at a separation voltage of 3 kV. This developed method has been applied to the beer samples, and acceptable recovery could be obtained ranging from 84.5 to 108%. The assay results indicated that this AuNP/rGO composite electrode has the advantages of simple preparation, low working potential (+ 0.65 V vs. SCE), good sensitivity (0.13~0.87 μM), and satisfactory reproducibility. This proposed method provides an alternative for rapid analysis of food safety.

Reduced Graphene Oxide as a Monolithic Multifunctional Conductive Binder for Activated Carbon Supercapacitors.

Using reduced graphene oxide (r-GO) as a multifunctional conductive binder, a simple, cost-effective, and environmentally friendly approach is developed to fabricate activated carbon/reduced graphene oxide (AC/r-GO) composite electrodes for supercapacitors with outstanding performance. In such a composite, r-GO provides several much needed critical functions: r-GO not only serves as the binder material improving the AC particle/particle cohesion and electrode-film/substrate adhesion but also improves the electrical conductivity of the composite and provides additional surfaces for ion adsorption. Furthermore, during electrode fabrication, initial GO precursor functions as an effective dispersant for AC, resulting in a stable electrode material slurry. Employing characterization by advanced microscopy techniques, we show that AC and r-GO assemble into an interconnected network structure, resulting in a composite with high specific capacitance, excellent rate capability, and long cycling life stability. Such high-performance electrodes coupled with their relatively simple, scalable, and low-cost fabrication process thereby provide a clear pathway toward large-scale implementation of supercapacitors.

Antimony/reduced graphene oxide composites as advanced anodes for potassium ion batteries

The abundance of sodium and potassium elements in the earth has trigged great research interests in Na-ion and K-ion batteries. Compared to Li-ion batteries, slashed fabrication cost has been predicated for Na-ion and K-ion batteries, making them promising candidates for stationary energy storage. Potassium ion has a much larger radius than that of lithium ion, which would lead to a more severe volume change during K ions insertion. An intriguing question is whether the electrode optimization strategies developed in Li-ion batteries could be extended to K-ion batteries. In this study, Sb is used as a model alloy anode to explore the effect of nanocarbon incorporation on the cyclic stability. Through the preparation of Sb/reduced graphene oxide composite electrode, a reversible capacity of over 300 mAh/g is obtained with decent capacity retention. In contrast, neat Sb shows a fast capacity fading due to the volume expansion during alloying with K ions. This study suggests that the preparation of alloy/nanocarbon composite remains an effective approach in developing advanced anodes for K-ion batteries. Schematic of the materials synthesis process: (a) GO precursor; (b) Adsorption of Sb3+ on the surface of GO and (c) thermal annealing to reduce GO (into -rGO) and SbCl3 (into Sb) nanoparticles.

Fabrication of nickel coated graphene oxide composite electrode for sensitive determination of Rutin

Nickel nanoparticles incorporated with graphene oxide composite-glassy carbon electrode (Ni-GO/GCE) was constructed via a facile electrochemical method for sensitive and selective determination of rutin. The surface morphology, surface chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviour of rutin on the Ni-GO/GCE was investigated by using of cyclic voltammetry technique. The composite electrode was also used for the detection of rutin with square wave voltammetry. The results indicated that under optimized conditions, the anodic peak current (Ipa) of rutin was found to be proportional to its concentration over two linear ranges 1.1 × 10−8–1.0 × 10−6 mol L−1 and 2.2 × 10−6–1.5 × 10−5 mol L−1, and a low detection limit of 3.2 × 10−9 mol L−1 was observed with the developed electrode. Interference studies were also performed in the presence of inorganic and organic compounds. Moreover, the Ni-GO/GCE was successfully applied for the determination of rutin in pharmaceutical formulations and remarkable sensitivity with acceptable recoveries were obtained.

All-Solid-State Supercapacitor Based on Graphene Oxide Composite Electrodes

Supercapacitors are a promising energy storage device for portable products, electric vehicles, and smart grid applications. However, the major scientific challenge in this system is to significantly increase energy density. This study expands energy density by constructing an all-solid-state supercapacitor with graphene oxide (GO) based composite electrodes and gel polymer electrolyte (GPE). Composite electrodes integrating nickel hydroxide (Ni(OH)2) and reduced graphene oxide (RGO) fabricated through a hydrothermal process are validated via x-ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR. Electrochemical performance of the composite electrode and all-solid-state supercapacitors are further examined by electrochemical procedures. The high resistance of metal oxide is shown to be overcome, and performance of the composite electrode approaches currently available published data. An all-solid-state supercapacitor with expanded operation window up to 3 V is demonstrated.

Flexible polymer solar cells based on Ag metallic grids and functional reduced graphene oxide composite electrode

By combining the appropriate Ag metallic grids with a thin functional reduced graphene oxide (MGs/F-rGO) film, a suitable photoelectric flexible electrode of the polymer solar cells (PSCs) is obtained. The conductivity and transmission of the MGs/F-rGO composited films can be improved by HNO3 modified. The optimized sheet resistance and transmission of the flexible electrode achieve to 25 Ω □−1 and 83% at 550 nm wavelength. Flexible PSCs with the MGs/F-rGO electrode show 5.63% power conversion efficiency. The photoelectric properties of the MGs/F-rGO film comparable with that of ITO substrates guarantee a high short current and an enhanced PCE of the solar cells. This method provides a feasible way for fabricating low-cost and flexible PSCs.

All-Solid-State Supercapacitor Based on Graphene Oxide Composite Electrodes

Supercapacitors and lithium ion batteries combined are promising hybrid energy storage for portable products, electric vehicles, and smart grid applications. However, the major scientific challenge in this system is to significantly increase the energy density of supercapacitors or raise the power density of lithium ion battery to enhance flexibility for various energy demands. This study aims to extend the energy density while maintain high specific capacitance through modification of electrodes with graphene oxide (GO) based materials. To prevent leakage of electrolyte, gel polymer electrolyte (GPE) consisting of lithium salt is selected, and it is also able to enhance the mechanical property of the capacitor. GO synthesized by chemical methods from graphite powder is employed because chemically functionalized surface of GO sheet can exhibit derived hydroxyl groups, epoxy groups, and active edges with carboxylic acid groups. Engineering of these functional groups in GO can potentially affect the surface adsorption and in turn improve the performance of capacitors. In this study, modification of GO surface is conducted and its effects on the all-solid-state supercapacitor are investigated. Characterizations of functionalized graphene oxide have been conducted with x-ray diffraction (XRD), scanning electron microscopy (SEM), and FTIR. Electrochemical performance of these electrodes is investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.

Nanostructured 3D zinc cobaltite/nitrogen-doped reduced graphene oxide composite electrode for supercapacitor applications

Abstract This paper reports the electrochemical performance of a binder-free supercapacitor electrode based on ZnCo 2 O 4 nanoflakes and N-doped reduced graphene oxide (rGO). The morphology of ZnCo 2 O 4 was tailored by changing the substrate from bare Ni foam (NiF) to rGO-supported NiF and then to N-doped rGO-supported NiF. The N-doped electrode exhibited superior electrochemical performance, i.e., high specific capacitance (1613 F g −1 at 1 A g −1 ) and excellent cycling stability (97.3% after 5000 cycles). An asymmetric supercapacitor based on this nanohybrid exhibited a high energy density of 36.5 Wh kg −1 . This excellent electrochemical performance highlights the potential of this electrode for next-generation supercapacitors.

A Facile Electrophoretic Deposition Route to the Fe3O4/CNTs/rGO Composite Electrode as a Binder-Free Anode for Lithium Ion Battery.

Fe3O4 is regarded as an attractive anode material for lithium ion batteries (LIBs) due to its high theoretical capacity, natural abundance, and low cost. However, the poor cyclic performance resulting from the low conductivity and huge volume change during cycling impedes its application. Here we have developed a facile electrophoretic deposition route to fabricate the Fe3O4/CNTs (carbon nanotubes)/rGO (reduced graphene oxide) composite electrode, simultaneously achieving material synthesis and electrode assembling. Even without binders, the adhesion and mechanical firmness of the electrode are strong enough to be used for LIB anode. In this specific structure, Fe3O4 nanoparticles (NPs) interconnected by CNTs are sandwiched by rGO layers to form a robust network with good conductivity. The resulting Fe3O4/CNTs/rGO composite electrode exhibits much improved electrochemical performance (high reversible capacity of 540 mAh g-1 at a very high current density of 10 A g-1, and a remarkable capacity of 1080 mAh g-1 can be maintained after 450 cycles at 1 A g-1) compared with that of commercial Fe3O4 NPs electrode.

Pt-Supported Carbon Nanotubes/Reduced Graphene Oxide Composite Electrodes for a Methanol Oxidation

Pt-Supported Carbon Nanotubes/Reduced Graphene Oxide Composite Electrodes for a Methanol Oxidation

Hydrothermal Synthesis of Vanadium Pentoxides–Reduced Graphene Oxide Composite Electrodes for Enhanced Electrochemical Energy Storage

Graphene-based nanomaterials (graphene nanosheets/graphene nanoribbons) decorated with vanadium pentoxide (V 2 O 5 ) nanobelts ( i.e. GVNBs) were synthesized via one-step low-temperature facile hydrothermal/solvothermal method as high-performance electrochemical composite electrodes. VNBs were formed in the presence of graphene oxide (GO), a mild oxidant, which transforms into reduced GO (rGO HT ) assisted in enhancing the electronic conductivity with mechanical strength for GVNBs. From surface sensitive electron microscopy and spectroscopy structural characterization techniques and analyses, rGO HT nanosheets/ nanoribbons appear to be inserted into and coated with the layered crystal structure of VNBs, which further confirmed the enhanced electrical conductivity of VNBs. The electrochemical energy storage capacity of GVNBs is investigated using electrochemistry and the specific capacitance C s are determined from both the cyclic voltammetry (CV) with scan rate and galvanostatic charge/discharge V-t profiles with varying current density. The GVNBs having rGO-rich composite V 1 G 3 (V 2 O 5 /GO = 1:3) showed superior performance followed by V 2 O 5 -rich V 3 G 1 (V 2 O 5 /GO = 3:1) as compared with V 1 G 1 (V 2 O 5 /GO = 1:1) composites besides pure component (rGO HT and V 2 O 5 ) materials. Moreover, V 1 G 3 and V 3 G 1 composites showed excellent cyclic stability and the capacitance retention of > 80% after 200 cycles. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters (charge transfer and solution resistance, double layer and low frequency capacitance). These findings highlight the comparative performance of nanocomposite hybrid electrode materials.

Enhanced High Rate Performance of a NaTi2(PO4)3/Reduced Graphene Oxide Composite Electrode Via Pyro Synthesis for Sodium Ion Batteries

The present study reports on a highly rate capable NASICON-structured NaTi2(PO4)3/ reduced graphene oxide (NTP/rGO) composite electrode synthesized by polyol-assisted pyro synthesis for Na-ion batteries (NIBs). X-ray diffraction (XRD) studies confirmed the presence of a rombohedral NaTi2(PO4)3 phase in the composite while Raman spectroscopy studies helped to identify the existence of rGO in the composite. Electron microscopy studies established that NaTi2(PO4)3 nanoparticles of average sizes ranging between 20 and 30 nm were uniformly distributed and embedded on the GO sheets. When tested for sodium storage properties, the obtained NTP/rGO composite electrode registered high rate capacities (95 mAh g-1 at 9.2 C and 78 mAh g-1 at 36.8 C) when compared to that of the NTP/C electrode (~1 mAh g-1 at 9.2 and 36.8 C). The enhanced performance of the composite electrode can be attributed to the nano-sized NaTi2(PO4)3 particles with shorter diffusion path lengths embedded on the rGO sheets with enhanced electrolyte/electrode contact areas that ultimately leads to an improvement in the electrical conductivity at high current densities. Ex-situ XANES studies confirmed reversible Na-ion intercalation/de-intercalation into/from NTP/rGO. The study thus demonstrates that the NaTi2(PO4)3/rGO nanocomposite electrode is a promising candidate for the development of high power/energy density anodes for NIBs.

Electrochemical Property of Platinum Supported on Thiol-Attached Reduced Graphene Oxide Composite Electrode for Fuel Cells

The direct methanol fuel cells (DMFCs) have been received much attention as promising energy converters in the portable application because of high energy density, low operating temperature, low fuel price and low pollutant emission. However, although there are many advantage of DMFC, commercialization of DMFCs is difficult due to poor methanol oxidation kinetics, nondurable Pt-based catalysts, expansive price and poison of Pt by formation of CO-like intermediates [1]. To overcome these problems, many studies have progressed with numerous scientists. One of the methods is to modify supports like carbon material. Among many carbon materials such as carbon black, carbon nanotubes, graphene and carbon fiber, the graphene have unique properties which are planar structure, high surface area and outstanding mechanical and chemical properties [2, 3]. However, the Pt-graphene used in fuel cell has low electrocatalytic activity because of weak interaction between the graphene used as support and Pt particles. Recently, to overcome the low electrocatalytic activity, many efforts for modification of RGO surface have been devoted. It has been studied by considering conducting polymer, and surfactant dispersant and substitution materials of functional groups [4,5]. The key point for maximizing elelctrocatalytic acticity is dipersion, particle size and chemical composition of Pt particles. In this study, we present Platinum (Pt) supported thiol-attached reduced graphene oxide (RGO-S). The functional groups of GO were substituted for thiol (SH), which result from strong nucleophilic substitution reaction. The sulfur (S) that has high affinity to metal combines with Pt by strong covalent bond. In conclusion, The RGO-S-Pt composite was synthesized and showed that the RGO-S-Pt composite was better than RGO-Pt composite in terms of electrocatalytic activity. Also, the electrocatalytic activity was different according to the various weight ratios of thiol. Especially, the RGO-S-Pt composite that has weight ratio of one (GO) to five (SH) presented the highest performance in terms of electrocatalytic acticity. Acknowledgments This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning, Korea (Grant No.: NRF-2011-0009007).