Low-cost Graphene Research Articles

Low-cost transparent graphene electrodes made by ultrasonic substrate vibration-assisted spray coating (SVASC) for thin film devices

In an attempt to replace expensive and rigid transparent conductive oxides, used as electrodes in thin film devices, in this study, transparent graphene electrodes (TGEs) are fabricated by conventional spray coating and ultrasonic substrate vibration-assisted spray coating. Systematic characterizations of the TGEs and indium tin oxide (ITO) demonstrate comparable and even better surface and morphological characteristics, film coverage, surface potential distribution and suitable work function of the spray-on TGEs compared to those of the reference ITO electrode. A lower transmittance, electrical conductivity and charge quenching potential are observed in the TGEs compared to those of the reference ITO, which may be further improved by process optimization. As a proof of concept, the TGE was incorporated into a perovskite solar cell, where power conversion efficiency of 3.54% was achieved, which is promising given that the developed graphene electrode was fabricated using scalable and low-cost spray coating.

Two steps synthesis approach of MnO2/graphene nanoplates/graphite composite electrode for supercapacitor application

MnO2/GNPs-PVDF/graphite capacitive electrode is prepared by two steps synthesis approach, where low cost graphene nanoplates (GNPs) which show the benefits of single-layer graphene and highly graphitic carbon, are initially mixed with 8 wt% polyvinylidene fluoride (PVDF) binder polymeric solution via a slurry procedure. Slurry of GNPs-PVDF composite is then pasted and pressed onto a flexible graphite substrate for the post anodic deposition of thin MnO2 film with relaxed structure. The MnO2 film deposited on GNPs-PVDF/graphite support shows better capacitive performance than that obtained by direct deposition on graphite substrate or those reported for counter electrodes prepared by one pot synthesis, as it exhibits specific capacitance (SC) of 855 F g-1 at 1.3 mA cm−2, excellent rate capability and most importantly, maintains capacitance retention (CR) of 105% after 2000 cycles of charging and discharging at 3.8 mA cm−2. This unique capacitive performance is attributed to the facilitation of ion accessibility and electron transfer through the MnO2 film, which stabilized by MnO2-GNPs bond interaction. If considering that GNPs can be easily mass produced from graphite; the structural stability and excellent capacitive performance suggest that MnO2/GNPs-PVDF composite supported on flexible graphite substrate is a promising electrode material for future energy storage applications.

Synergistically Enhanced Electrocatalytic Performance of an N-Doped Graphene Quantum Dot-Decorated 3D MoS2-Graphene Nanohybrid for Oxygen Reduction Reaction.

Nitrogen-doped graphene quantum dots (N-GQDs) were decorated on a three-dimensional (3D) MoS2–reduced graphene oxide (rGO) framework via a facile hydrothermal method. The distribution of N-GQDs on the 3D MoS2–rGO framework was confirmed using X-ray photoelectron spectroscopy, energy dispersive X-ray elemental mapping, and high-resolution transmission electron microscopy techniques. The resultant 3D nanohybrid was successfully demonstrated as an efficient electrocatalyst toward the oxygen reduction reaction (ORR) under alkaline conditions. The chemical interaction between the electroactive N-GQDs and MoS2–rGO and the increased surface area and pore size of the N-GQDs/MoS2–rGO nanohybrid synergistically improved the ORR onset potential to +0.81 V vs reversible hydrogen electrode (RHE). Moreover, the N-GQDs/MoS2–rGO nanohybrid showed better ORR stability for up to 3000 cycles with negligible deviation in the half-wave potential (E1/2). Most importantly, the N-GQDs/MoS2–rGO nanohybrid exhibited a superior methanol tolerance ability even under a high concentration of methanol (3.0 M) in alkaline medium. Hence, the development of a low-cost metal-free graphene quantum dot-based 3D nanohybrid with high methanol tolerance may open up a novel strategy to design selective cathode electrocatalysts for direct methanol fuel cell applications.

Electroless Nickel Deposition: An Alternative for Graphene Contacting

We report the first investigation into the potential of electroless nickel deposition to form ohmic contacts on single layer graphene. To minimize the contact resistance on graphene, a statistical model was used to improve metal purity, surface roughness, and coverage of the deposited film by controlling the nickel bath parameters (pH and temperature). The metalized graphene layers were patterned using photolithography and contacts deposited at temperatures as low as 60 °C. The contact resistance was 215 ± 23 Ω over a contact area of 200 μm × 200 μm, which improved upon rapid annealing to 107 ± 9 Ω. This method shows promise toward low-cost and large-scale graphene integration into functional devices such as flexible sensors and printed electronics.

Toward Graphene-Based Passive UHF RFID Textile Tags: A Reliability Study

This paper discusses the fabrication, wireless performance, and reliability of graphene-based passive ultrahigh-frequency radio-frequency identification (RFID) tags on a fabric substrate. The conductive ink comprising functionalized graphene nanoplatelets is deposited directly on a cotton fabric substrate to fabricate the tag antennas. After attaching the chips, the tag performance is evaluated through wireless tag measurements before and after high-humidity conditions, bending, and stretching. Initially, the peak read range of the tag is about 1.6 m, which increases to 3.2 m in 100% humidity conditions. Additionally, after drying, the performance of the tag returns back to normal. In a bending test, the read range of a bent tag decreases below 1 m. Furthermore, the read range of the tag in a nonbended state gradually decreases and is about 1.1 m after 100 bending cycles. According to our measurements, stretching has a serious detrimental effect on these tags and they cannot be considered stretchable. However, these initial results show that this low-cost and eco-friendly graphene RFID tag has a remarkable and unique response to moisture and high reliability in harsh bending conditions. Overall, it also has a strong potential to be used in future wearable sensor applications.

High throughput transfer technique: Save your graphene

The development rate of graphene-related research is tremendous. New methods of graphene growth and transfer are reported on a regular basis, trending towards large-scale. Nevertheless, the fabrication of high-yield and low-cost graphene devices is still challenging. In this work, we approach this problem from a technological point of view and propose a new, so-called “high-throughput transfer technique”. The technique allows a semi-automatic transfer of graphene films right at the desired places on a wafer. We demonstrate the applicability of our method by aligning 52 graphene devices on a 4-inch wafer using only 4 cm2 of graphene. The overall yield of this process is over 90%.

Graphene oxide – Polyvinyl alcohol nanocomposite based electrode material for supercapacitors

Supercapacitors are high capacitive energy storage devices and find applications where rapid bursts of power are required. Thus materials offering high specific capacitance are of fundamental interest in development of these electrochemical devices. Graphene oxide based nanocomposites are mechanically robust and have interesting electronic properties. These form potential electrode materials efficient for charge storage in supercapacitors. In this perspective, we investigate low cost graphene oxide based nanocomposites as electrode material for supercapacitor. Nanocomposites of graphene oxide and polyvinyl alcohol were synthesized in solution phase by integrating graphene oxide as filler in polyvinyl alcohol matrix. Structural and optical characterizations suggest the formation of graphene oxide and polyvinyl alcohol nanocomposites. These nanocomposites were found to have high specific capacitance, were cyclable, ecofriendly and economical. Our studies suggest that nanocomposites prepared by adding 0.5% wt/wt of graphene oxide in polyvinyl alcohol can be used an efficient electrode material for supercapacitors.

Si-doped graphene: A promising metal-free catalyst for oxidation of SO2

This study reports favorable reaction mechanisms of SO2 oxidation by molecular O2 over Si-doped graphene by means of DFT calculations. The SO2 oxidation reaction proceeds through the following elementary steps (a) SO2+O2⿿Oads+SO3 and (b) Oads+SO2⿿SO3. It is found that the first and second steps are fulfilled via the Langmuir⿿Hinshelwood (LH) and Eley⿿Rideal (ER) mechanisms, with an activation energy of 4.7 and 9.5kcal/mol, respectively. Results show that the low-cost Si-doped graphene can be used as an efficient catalyst for SO2 oxidation at room temperature.

Hydroiodic Acid Reduced Graphene Hybrid with δ-MnO2 for Electrode Material in Supercapacitors

In this paper, we report a method for the further reduction of the low-cost graphene (LG) via hydroiodic acid to synthesize graphene hybrid with varying content of δ-MnO2. Scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were implemented to characterize the surface and structural properties of the reduced graphene (LGHI) and graphene-MnO2 composites (GM). It can be observed that the thickness of LGHI layers is about 10∼200 nm and as-prepared GM composites have a uniform morphology possessing a honeycomb structure. XRD results indicate that MnO2 in the GM exists as a δ-crystallographic structure of low crystallinity. Cyclic voltammetry (CV) curves, galvanostatic charge/discharge (GDC) curves and electrochemical impedance spectroscopy (EIS) were utilized in a three-electrode system to systematically investigate the electrochemical performance of varying δ-MnO2 content materials. Results reveal that once the mass fraction of δ-MnO2 in GM reaches 93.1% (labeled GM-6), the specific maximum capacitance of GM was found to be 783 F/g, 496 F/g, 345 F/g and 210 F/g at a current density of 0.3 A/g, 1 A/g, 3 A/g and 10 A/g, respectively. Moreover, GM-6 maintains almost 94.5% of its original specific capacitance after 5000 continuous cycles of charge-discharge. These promising results demonstrate that GM-6 has great potential to be utilized as an electrode material for supercapacitor applications.

Graphene coated nonwoven fabrics as wearable sensors

A low cost graphene coated nonwoven fabric wearable sensor can monitor a series of human motions including pulse and respiration.

Eco-friendly production of high quality low cost graphene and its application in lithium ion batteries

A green method is discussed in which hydrogen exfoliates industrial grade graphite materials into high quality graphene with impressive properties for advanced lithium-ion batteries.

Meat species identification using DNA-redox electrostatic interactions and non-specific adsorption on graphene biochips

This study describes the development of a novel electrochemical biosensor for meat species identification using DNA-redox electrostatic interactions and the nonspecific adsorption of these molecules on graphene biochips. The ruthenium hexamine molecule [Ru(NH3)6]3+, or RuHex, was observed to form complexes with free DNA in solution that adsorbed onto graphene surfaces, enabling the development of a rapid, high-sensitivity DNA biosensor. Reproducible cathodic current signals were generated from these low-cost graphene biochips, both in the presence and absence of dsDNA and loop-mediated isothermal amplification (LAMP) amplicons. The combination of the DNA-redox molecule complexes and the graphene surface therefore provided a novel detection strategy. This new biosensor was able to identify different meat species based on the isothermal amplification of target genes followed by electrochemical detection with square wave voltammetry. To optimize the specificity and sensitivity of the biosensor, the LAMP parameters were investigated under varying isothermal conditions using varying concentrations of reagents and target DNA, and with different combinations of newly designed loop primers. Using these novel biomarkers along with the new on-chip detection strategy, we observed limits of detection of target DNA of 1 pg/μL and 100 pg/μL for chicken and pork species, respectively.

Wearable energy-dense and power-dense supercapacitor yarns enabled by scalable graphene-metallic textile composite electrodes.

One-dimensional flexible supercapacitor yarns are of considerable interest for future wearable electronics. The bottleneck in this field is how to develop devices of high energy and power density, by using economically viable materials and scalable fabrication technologies. Here we report a hierarchical graphene–metallic textile composite electrode concept to address this challenge. The hierarchical composite electrodes consist of low-cost graphene sheets immobilized on the surface of Ni-coated cotton yarns, which are fabricated by highly scalable electroless deposition of Ni and electrochemical deposition of graphene on commercial cotton yarns. Remarkably, the volumetric energy density and power density of the all solid-state supercapacitor yarn made of one pair of these composite electrodes are 6.1 mWh cm−3 and 1,400 mW cm−3, respectively. In addition, this SC yarn is lightweight, highly flexible, strong, durable in life cycle and bending fatigue tests, and integratable into various wearable electronic devices.

High Quality Monolayer Graphene Synthesized by Resistive Heating Cold Wall Chemical Vapor Deposition.

Emerging flexible and wearable technologies such as healthcare electronics and energy-harvest devices could be transformed by the unique properties of graphene. The vision for a graphene-driven industrial revolution is motivating intensive research on the synthesis of (1) high quality and (2) low cost graphene. Hot-wall chemical vapour deposition (CVD) is one of the most competitive growth methods, but its long processing times are incompatible with production lines. Here we demonstrate the growth of high quality monolayer graphene using a technique that is 100 times faster than standard hot-wall CVD, resulting in 99% reduction in production costs. A thorough complementary study of Raman spectroscopy, atomic force microscopy, scanning electron microscopy and electrical magneto-transport measurements shows that our cold wall CVD-grown graphene is of comparable quality to that of natural graphene. Finally, we demonstrate the first transparent and flexible graphene capacitive touch-sensor that could enable the development of artificial skin for robots.

A Disposable and Flexible Graphene Electrode Fabricated by Inkjet Printing of an Aqueous Surfactant-free Graphene Oxide Dispersion

Abstract Herein, the fabrication of a simple, low-cost, disposable, and flexible graphene (GP) electrochemical electrode by inkjet printing of the aqueous graphene oxide (GPO) dispersion ink was investigated. In terms of conductivity enhancement, the inkjet-printed GPO chip was chemically reduced, and exhibited high electrochemical response, reactivity, and stability. The electrode is a promising candidate for electrochemical applications.

Expandable-graphite-derived graphene for next-generation battery chemistries

Lithium–sulfur and lithium–air batteries offer theoretical energy densities an order of magnitude higher than that of current lithium-ion batteries and are considered as promising candidates as the next-generation battery chemistries. For an efficient use of these new battery chemistries, careful selection of suitable electrode materials/structures is critical. Graphene, a unique two-dimensional nanomaterial, with its superior electronic conductivity, mechanical strength, and flexibility has been successfully applied in battery studies. Graphene, even with imperfect layers, will be of great interest to battery industrial applications if the manufacturing cost is reduced. Herein, we demonstrate the application of low-cost graphene sponge/sheets derived from expandable graphite in both lithium–sulfur and hybrid lithium–air batteries, respectively, as a cathode conductive matrix to accommodate the soluble polysulfides and as a catalyst for the oxygen reduction reaction. High utilization of active materials and good cycling stability are realized in lithium–sulfur and hybrid lithium–air batteries by employing this low-cost material, demonstrating its promise for use in next-generation battery chemistries.

Graphene on paper: a simple, low-cost chemical sensing platform.

Graphene layers have been transferred directly on to paper without any intermediate layers to yield G-paper. Resistive gas sensors have been fabricated using strips of G-paper. These sensors achieved a remarkable lower limit of detection of ∼300 parts per trillion (ppt) for NO2, which is comparable to or better than those from other paper-based sensors. Ultraviolet exposure was found to dramatically reduce the recovery time and improve response times. G-paper sensors are also found to be robust against minor strain, which was also found to increase sensitivity. G-paper is expected to enable a simple and inexpensive low-cost flexible graphene platform.

Fast adsorption of nickel ions by porous graphene oxide/sawdust composite and reuse for phenol degradation from aqueous solutions

This work describes the preparation of an effective and low-cost porous graphene oxide/sawdust composite by a freeze-drying method. The composite exhibits a strong ability to adsorb nickel ions. The nickel ions adsorbed on graphene oxide/sawdust composite was reduced by sodium borohydride to generate a catalyst which was used in the degradation of phenol in water. The composite and the catalyst were characterized by XPS, FTIR, XRD and SEM. The adsorption of nickel ions by graphene oxide/sawdust composite was initially very fast and then slowly reached equilibrium in around 30min. The adsorption of nickel ions by the composite could be well-described by the Freundlich isotherm model and the pseudo-second order kinetic model. The performance of the catalyst in phenol degradation was studied as a function of reaction time, dosage, temperature and initial pH. It was found that the catalyst optimally improved the degradation rate at pH 10 with a dose of 2g/L in about 30min. The results show that the degradation of phenol was an endothermic reaction and was a good fit to the Langmuir isotherm model.

A powerful tool for graphene functionalization: Benzophenone mediated UV-grafting

The surface modification of graphene is of fundamental importance when working on the fabrication of high performing polymeric nanocomposite exploiting the exciting properties of this carbon-based material. Using low cost graphene oxide as starting material, trading on its richness of –OH groups and its ability to be reduced under UV light, a facile two-step UV-based process for the reduction to graphene and the simultaneous covalent grafting of initiating moieties at its surface is here proposed. This procedure enables the subsequent photo-grafting of a great variety of monomers for graphene surface functionalization.Chemical, structural and electrical analysis of the functionalized graphene sheets demonstrated the reduction of the starting oxide and the grafting of the initiator and of the acrylic monomers used in this study. This procedure opens the route for a low cost production of grafted graphene that can be easily dispersed in organic matrices, in order to produce highly performing functional materials.

Graphene: Highly Stretchable Piezoresistive Graphene–Nanocellulose Nanopaper for Strain Sensors (Adv. Mater. 13/2014)

A strategy based on graphene and nanocellulose is developed by P. S. Lee and co-workers on page 2022, for the fabrication of highly stretchable strain sensors for human-motion detection. The image shows the 3D macroporous structure of the composite film from intertwined nano cellulose fibrils and crumpled graphene. The stretchable sensors made from low-cost and solutionprocessable graphene and nano cellulose hold promising applications in emerging human-interactive devices.