Large-scale Synthesis Of Graphene Research Articles

Ultrafast alternating-current exfoliation toward large-scale synthesis of graphene and its application for flexible supercapacitors

To facilitate the transition of laboratory research to industrial applications, it is critical to establish a reliable protocol for the mass synthesis of high-quality graphene. Here, we present an efficient electrochemical intercalation-based exfoliation approach utilizing alternating current that allows for the production of sub-kilogram quantities of graphene. This strategy involves repeatedly intercalating foreign anions and cations into the interlayer gaps of dual-graphite electrodes, accelerating the graphite expansion process and maximizing the exfoliation efficiency of both electrodes while inhibiting excessive anodic oxidation. The exfoliation process leads to high-yield graphene nanosheets (92 %, primarily 1–3 layers) with minimal structural deterioration (ID/IG ratio of 0.05), high purity (2.1 at% oxygen), and outstanding electrical property (7.28 × 104 S m−1). Notably, our scaled-up manufacturing technique produces a record-breaking throughput of 135 g h−1, improving on the best-reported exfoliation efficiency with direct current by 35%. Furthermore, the as-made graphene demonstrates a large reversible capacity of 102 mF cm−2 for flexible supercapacitors, with robust cyclability with 99.5% after 10,000 cycles, excellent mechanical flexibility, and exceptional serial integration for adjustable voltage output. The efficient and scalable method presents a significant advancement in the large-scale manufacture of graphene, with potential for widespread industrial applications.

Graphene/Graphene Derivatives from Coal, Biomass, and Wastes: Synthesis, Energy Applications, and Perspectives

In the last decade, there has been a phenomenal development in the commercially viable, large-scale synthesis of graphene, a multifunctional advanced carbon nanomaterial, which is gaining popularity for its diverse range of applications, especially in energy storage, composites, sensors, and membranes. With the increasing demand, a large number of worldwide research efforts have been employed, resulting in a series of enormous breakthroughs both in its fundamental science and innovative applications. The earlier reviews on graphene show that the increase in the production yield is often accompanied by the generation of substandard graphene quality, making the process unsuited for commercialization. However, recent studies on graphene synthesis have shown the use of naturally available carbonaceous sources for the production of low-cost graphene derivatives is becoming an emerging trend in graphene research. In this present review, the most recent advances in the synthesis of high-quality graphene from solid carbon precursors, particularly abundant coal, biomass, and waste materials, have been extensively discussed along with their potential scalability for commercial production. The quality and yield of these graphene derivatives synthesized through different methods like chemical vapor deposition, exfoliation, laser-induced, microwave irradiation, and chemical methods are also examined to determine the best-suited synthetic methodology from the available literature. The utilization of graphene derivatives in the energy sector was further discussed, particularly in the emerging field of energy storage. Finally, the challenges and future prospects of this study are highlighted to have a better understanding of the current graphene production scenario, with an insight into the most efficient method for synthesizing high-purity low-cost graphene and their potential for scale-up and energy applications in the distant future.

Industrially scalable exfoliated graphene nanoplatelets by high-pressure airless spray technique for high-performance supercapacitors

The significance of Graphene-based materials in various energy conversion and storage devices has been increasing due to their high surface area helps to enhance the multidimensional storage capability. Even though a significant amount of work has been done on graphene synthesis, there is still a need for an economical and environmentally friendly large-scale graphene synthesis method. This work demonstrates the large-scale production of high-quality Graphene Nanoplatelets (GnPs) by high-pressure spray exfoliation to develop high-performance supercapacitors. The high-pressure exfoliated GnPs were used to construct symmetric supercapacitors and studied their performance in organic and aqueous electrolytes. The pronounced rectangularity of cyclic voltammetry (CV) curves in both electrolytes indicates the charge storage is mainly by electrical double layer mechanisms. Retaining rectangularity at very high scan rates (>1000 mV/s) in both electrolytes signifies the excellent rate performance of high pressure exfoliated GnP based supercapacitors. The maximum specific capacitance of 26 F g−1 in the organic electrolyte and 86 F g−1 in the aqueous electrolyte was experimentally demonstrated, comparatively better than many other graphene-based device reports. The high capacitance and energy retention in the organic and aqueous electrolyte at very high current densities (>15 A g−1) indicate the potential usage during the demand surge power supply of exfoliated GnPs for the commercialization of graphene-based supercapacitors.

Self-propagating high–temperature synthesis of porous graphene by magnesiothermic reaction as high–performance electrochemical electrode material

Graphene is widely used in supercapacitors due to its large specific surface area and excellent electrical conductivity. However, a large scale efficient and sustainable production of high–quality graphene is still an urgent challenge. We report a controllable self-propagating high–temperature synthesis (SHS) process to convert CO2 with a mixed powder of magnesium and zinc into porous graphene (PG). The prepared PG contains 3–6 layers, with a plenty of uniform 2–4 nm mesopores, and has a specific surface area as high as 1458 m2 g−1. The obtained PG was used as an electrode material for the supercapacitor and exhibited a superior capacitance performance. At a current density of 1 A g−1, the specific capacitance can reach 177 F g−1. Capacitance retention rate is as high as 91% after 10,000 cycles at a current density of 5 A g−1. In addition, the charge–discharge curve remains approximately triangular at a current density of 20 A g−1, which shows satisfactory capacitance properties. We expect that our results will contribute to the development of the large-scale graphene synthesis technology based on a use of the SHS method aimed for the application as high–performance supercapacitor materials.

Defect-Free Mechanical Graphene Transfer Using n-Doping Adhesive Gel Buffer.

The synthesis of uniform low-defect graphene on a catalytic metal substrate is getting closer to the industrial level. However, its practical application is still challenging due to the lack of an appropriate method for its scalable damage-free transfer to a device substrate. Here, an efficient approach for a defect-free, etchant-free, wrinkle-free, and large-area graphene transfer is demonstrated by exploiting a multifunctional viscoelastic polymer gel as a simultaneous shock-free adhesive and dopant layer. Initially, an amine-rich polymer solution in its liquid form allows for conformal coating on a graphene layer grown on a Cu substrate. The subsequent thermally cured soft gel enables the shock-free and wrinkle-free direct mechanical exfoliation of graphene from a substrate due to its strong charge-transfer interaction with graphene and excellent shock absorption. The adhesive gel with a high optical transparency works as an electron doping layer toward graphene, which exhibits significantly reduced sheet resistances without optical transmittance loss. Lastly, the transferred graphene layer shows high mechanical and chemical stabilities under the repeated bending test and exposure to various solvents. This gel-assisted mechanical transfer method can be a solution to connect the missing part between large-scale graphene synthesis and next-generation electronics and optoelectronic applications.

Convert waste petroleum coke to multi-heteroatom self-doped graphene and its application as supercapacitors

Graphene is being suggested as a replacement for activated carbon in energy storage devices ranging from supercapacitors to batteries. The generation of multi-heteroatom self-doped graphene structure from waste materials will be an efficient way to meet the energy requirements with its productive applications in energy devices. Here, we present a novel, high-yield synthetic strategy to prepare multi-heteroatom self-doped highly porous graphene nanosheet from Pet coke (petroleum coke). Following a comprehensive characterization of graphene using electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and its functionality in supercapacitor application is reported. The electrochemical performance of Pet graphene, in combination with 1 M H2SO4, is able to deliver specific capacitance as high as ~ 170 F/g in 0.5 A/g current density, with low equivalent series resistance. The fabricated symmetric device exhibited a maximum specific capacitance of 44 F/g at 0.5 A/g current density with an excellent energy density of ~ 8.8 Wh/Kg along with a power density of ~ 800 W/Kg at 0.5 A/g current density. The fabricated device also shows high cycling stability and Coulombic efficiency. The results establish a new protocol for the large-scale synthesis of graphene from carbonaceous waste materials, making it competitive with its low-cost counterparts.

Fast and controllable reduction of graphene oxide by low-cost CO2 laser for supercapacitor application

Direct reduction of graphene oxide has been regarded as the economically viable route for large-scale synthesis of graphene. However, the currently known methods suffer from either poor reduction efficiency or involve multi-step and energy-intensive reduction processes. Here, we demonstrate a remarkably fast, single step as well as highly efficient reduction technique to produce high-quality multilayer graphene film using a compact and low-cost CO2 laser pyrolysis. Thanks to the intrinsically high absorptivity of graphene oxide in the near- and mid-infrared regions, the irradiation of CO2 laser generates instantaneous and strong localized heating on it and thus burst apart the oxygen functional groups from the graphene oxide layers. The extent of reduction in the synthesized multilayer graphene films can be fruitfully controlled by variation of laser processing parameters such as laser intensity, scanning speed and shifting pitch. To prove the worth of this method, the graphene films were used as the binder-free and self-standing electrode for symmetric supercapacitor cell. The electrochemical performance data shows that specific capacitance and cyclic stability has a contrasting relation with the reduction efficiency. We believe that this CO2 laser-based reduction method could guarantee a high outturn of multilayer graphene and its composites for innumerable applications.

Electron Mobility across Grain Boundaries in Graphene Synthesized using Chemical Vapor Deposition Process

Chemical vapor deposition (CVD) is currently the only method for large-scale synthesis of graphene. However, the CVD process introduces grain boundaries (GBs) when individual grains coalesce with various mismatch angles. These GBs contain atomic dislocations and defects, which are believed to alter graphene's mechanical, electrical, and thermal properties. Specifically, the GBs can act as “potential barriers” when charges move from one grain to neighboring grains. This barrier effect will not only change the electrical conductivity but also the thermal conductivity of graphene. Besides high-resolution, 3-dimensional topography images, Atomic force microscopy (AFM) can also obtain the electrical properties at the nanoscale. In this report, the potential barrier effect of graphene GBs is studied with AFM. During the experiment, the probe is brought into contact with the graphene while positively (or negatively) biased. This process injects net charges into the graphene. The electrostatic potential across the GBs can be measured by AFM as an indication of the potential barrier effect. GBs with lower potential difference correspond to lower potential barrier, and vice versa. The dependency of the barrier effect on the mismatch angles was also measured. Considering the 6 folds’ symmetry of graphene atomic lattice, the mismatch angle is in the range of 0° ∼ 30°, with 30° the maximum mismatch angle. Our results can be well fitted with a sinusoidal function with π/3 period, which supports our hypothesis that higher mismatch angle contains higher density of dislocations and defects that increase the potential barrier of GBs.

Localized electronic states at grain boundaries on the surface of graphene and graphite

Recent advances in large-scale synthesis of graphene and other 2D materials have underscored the importance of local defects such as dislocations and grain boundaries (GBs), and especially their tendency to alter the electronic properties of the material. Understanding how the polycrystalline morphology affects the electronic properties is crucial for the development of applications such as flexible electronics, energy harvesting devices or sensors. We here report on atomic scale characterization of several GBs and on the structural-dependence of the localized electronic states in their vicinity. Using low temperature scanning tunneling microscopy and spectroscopy, together with tight binding and ab initio numerical simulations we explore GBs on the surface of graphite and elucidate the interconnection between the local density of states and their atomic structure. We show that the electronic fingerprints of these GBs consist of pronounced resonances which, depending on the relative orientation of the adjacent crystallites, appear either on the electron side of the spectrum or as an electron-hole symmetric doublet close to the charge neutrality point. These two types of spectral features will impact very differently the transport properties allowing, in the asymmetric case to introduce transport anisotropy which could be utilized to design novel growth and fabrication strategies to control device performance.

Low-temperature quantum transport in CVD-grown single crystal graphene

Chemical vapor deposition (CVD) is typically used for large-scale graphene synthesis for practical applications. However, the inferior electronic properties of CVD graphene are one of the key problems to be solved. Therefore, we present a detailed study on the electronic properties of high-quality single-crystal monolayer graphene. The graphene is grown via CVD on copper, by using a cold-wall reactor, and then transferred to Si/SiO2. Our low-temperature magneto-transport data demonstrate that the characteristics of the single-crystal CVD graphene samples are superior to those of polycrystalline graphene and have a quality which is comparable to that of exfoliated graphene on Si/SiO2. The Dirac point in our best samples occurs at back-gate voltages lower than 10 V, and a maximum mobility of 11,000 cm2/(V·s) is attained. More than 12 flat and discernible half-integer quantum Hall plateaus occur under a high magnetic field on both the electron and hole sides of the Dirac point. At a low magnetic field, the magnetoresistance exhibits a weak localization peak. Using the theory of McCann et al., we obtain inelastic scattering lengths of >1 µm, even at the charge neutrality point of the samples.

Sulfuric Acid Intercalated Graphite Oxide for Graphene Preparation

Graphene has shown enormous potential for innovation in various research fields. The current chemical approaches based on exfoliation of graphite via graphite oxide (GO) are potential for large-scale synthesis of graphene but suffer from high cost, great operation difficulties, and serious waste discharge. We report a facile preparation of graphene by rapid reduction and expansion exfoliation of sulfuric acid intercalated graphite oxide (SIGO) at temperature just above 100°C in ambient atmosphere, noting that SIGO is easily available as the immediate oxidation descendent of graphite in sulfuric acid. The oxygenic and hydric groups in SIGO are mainly removed through dehydration as catalyzed by the intercalated sulfuric acid (ISA). The resultant consists of mostly single layer graphene sheets with a mean diameter of 1.07 μm after dispersion in DMF. This SIGO process is reductant free, easy operation, low-energy, environmental friendly and generates graphene with low oxygen content, less defect and high conductivity. The provided synthesis route from graphite to graphene via SIGO is compact and readily scalable.

Large‐Scale Production of Nanographene Sheets with a Controlled Mesoporous Architecture as High‐Performance Electrochemical Electrode Materials

Graphene is considered as a rising-star material because of its unique properties and it is a promising material for applications in many fields. In recent years, experiments on graphene fabricated by using versatile methods have shed light on the crucial problem of aggregation and restacking, which is induced by strong π-π stacking and van der Waals forces, but preparation methods for real-world applications are still a great challenge. Here we report a facile, rapid, and environmentally friendly process, the burn-quench method, that allows large-scale and controlled synthesis of ordered mesoporous nanographene with 1-5 layers, which has a high surface area and electric conductivity. Electrodes composed of nanographene with a mesoporous architecture used both in electrochemical capacitors and lithium-ion batteries have a high specific capacitance, rate capability, energy density, and cyclic stability. Our results represent an important step toward large-scale graphene synthesis based on this new burn-quench method for applications in high-performance electrochemical energy storage devices.

Efficient and Large Scale Synthesis of Graphene from Coal and Its Film Electrical Properties Studies

Coal, which is abundant and has an incompact structure, is a good candidate to replace graphite as the raw material for the production of graphene. Here, a new solution phase technique for the preparation of graphene from coal has been developed. The precursor: graphene oxide got from coal was examined by atomic force microscopy, dynamic light scattering and X-ray diffraction, the results showed the GO was a small and single layer sheet. The graphene was examined by X-ray photoelectron spectroscopy, and Raman spectroscopy. Furthermore, graphene films have been prepared using direct solution process and the electrical conductivity and Hall effect have been studied. The results showed the conductivity of the films could reach as high as 2.5 x 10(5) Sm(-1) and exhibited an n-type behavior.

Large-scale synthesis of graphene by the reduction of graphene oxide at room temperature using metal nanoparticles as catalyst

A simple chemical approach has been developed for the synthesis of graphene through a mild reduction of graphene oxide (GO) using metal nanoparticles as the catalyst for the hydrolysis reaction of NaBH4 at room temperature. The morphology and structure of the graphene were characterized with atomic force microscopy and transmission electron microscopy. The reduction process and quality of graphene were followed and examined by UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. By this method, graphene can be prepared in large quantity without using toxic reducing agents such as hydrazine or its derivatives, making it environmentally benign. The reaction is conducted under mild conditions (room temperature), resulting in the formation of fewer defects. The method can be easily scaled up and the metal catalyst can be recycled.

Synthesis of Monolayer‐Patched Graphene from Glucose

The extraordinary electronic and mechanical properties of graphene have stimulated intense research on developing simple methods for the large-scale synthesis of graphene. High-quality large-area graphene films prepared by the chemical vapor deposition of various carbon-containing molecules on arbitrary substrates could meet the requirements of large-area electronic applications. For the industrial production of conductive graphene powder on the ton scale, 11–13] the chemical exfoliation of graphite minerals still remains the main manufacturing path. On the other hand, the exclusive two-dimensional polymerization of graphene-like structures from simple monomers still presents a challenge for carbon chemists. Further fine-tuning of the Fermi level of graphene by doping offers a way to control the electronic structure of carbonaceous materials and is of major interest for their application in electronics, electrodes, and catalysis. The electronic properties of doped graphene are strongly linked to the dopant concentration, which is only poorly controlled by current methods. It is therefore highly challenging but desirable to develop effective approaches for fabricating graphene that is cheap yet of high quality (e.g. high surface area, high conductivity, doping level, and uniform morphology) in a controlled manner. Herein we report a simple yet versatile approach for the synthesis of two-dimensional (2D) carbon materials ranging from free-standing monolayers to oligolayered graphene by the calcination of glucose, a most abundant, sustainable compound. In this synthesis only dicyandiamide (DCDA) was added for the temporary in situ formation of layered graphic carbon nitride (g-C3N4), which serves as a sacrificial template. This approach is also facile for gradually tuning the concentration of the nitrogen dopant in a broader range without disturbing the morphology of graphene. In a typical synthesis, the two-step heating of a mixture of DCDA and glucose under a protective flow of N2 directly resulted in freestanding graphene with a yield of 28–60% (calculated based on added carbon from glucose). The overall formation process is depicted in Figure 1: Thermal condensation of DCDA creates a layered carbon

Large-scale preparation of graphene sheets and their easy incorporation with other nanomaterials

Graphene dispersions with concentrations up to 0.5 mg/mL were produced by dispersion in N,N-dimethylformamide with the aid of polyacrylic acid. Graphene oxide could also be dispersed with even higher concentration (17 mg/mL), and this advantage was used for the large-scale synthesis of graphene. The good dispersion of graphene sheets also facilitated the preparation of a new hybrid material of graphene and Fe3O4 nanoparticles, which exhibited interesting magnetic properties.

Recent Progress on the Synthesis and Applications of Carbon Based Nanostructures

This article reviews the latest developments in the synthesis of Graphene, Carbon nanotubes and graphene/CNT based devices based on patents, patent applications and articles published in the last two years. A brief introduction about CNT and Graphene is presented, followed by the latest techniques and advanced processing for the large scale synthesis of Graphene and CNTs. Furthermore, a brief account of emerging devices based on applications of CNTs and graphene not limited to sensors, high speed electronics, energy harvesting and storage applications are presented.

A Novel Chemical Synthesis >1 μm2 Reduced Graphene Oxide Sheets

ABSTRACTIf graphene is to be incorporated into transistors, solar cells, and capacitors, a large-scale synthesis of graphene must be devised. This research developed an innovative, simple, and cost-efficient synthesis procedure, dispersing graphene oxide in an ethanol-water solvent and reducing slowly with sodium borohydride (NaBH4). Reducing graphene oxide in 75:25 and 50:50 H2O:ethanol solutions with 15 mmolar NaBH4 produced numerous single-layered reduced graphene oxide sheets >1 μm2, and sometimes even >2 μm2. The quality of these sheets was confirmed by Raman spectroscopy, XRD, TGA, TEM, ED, and HRTEM.

Graphene Metrology Using Fluorescence Quenching of Different Fluorescent Dyes

ABSTRACTThe unique structure and properties of graphene initiated broad fundamental and technological research, and highlighted graphene as a new candidate for various applications such as energy storage, solar cells and electronic devices. Chemical vapor deposition (CVD) has been utilized for industrial large-scale synthesis of graphene. Regardless of the synthesis process, graphene should be transferred to arbitrary substrates for different applications. The transfer processes, introduce defects such as wrinkles and cracks in graphene which compromise the properties and applications. In recent years, fundamental research has been focused on characterization of graphene to develop new techniques for large-scale, high-resolution graphene metrology. Herein, a complementary high throughput metrology technique using fluorescent quenching is further investigated for different fluorescent dyes to characterize CVD synthesized graphene.

Effects of Process Tube Position on Properties of Graphene Layers

ABSTRACTGraphene, with unique electrical, optical and mechanical properties is a promising material in industrial applications, such as batteries, supercapacitors, transistors and semiconductor devices. These potential applications of graphene have motivated the development of large-scale synthesis of graphene on copper substrates by chemical vapor deposition (CVD). To enable practical applications of large-area, high quality graphene layers at the centimeter and wafer scales, process control needs to be implemented for optimizing the morphology and electrical properties and enable repeatable growth-cycle of graphene layers for process-line implementation. Here we investigate the effects of process quartz-tube position on the structural properties of graphene. Furthermore, we describe a procedure for process optimization of the growth parameters. Graphene is grown on copper foils by CVD, and transferred to the SiO2/Si and glass substrates. The detailed characterization of the graphene layers are conducted using Raman spectroscopy, optical microscopy (OM), scanning electron microscopy (SEM) and UV-vis spectroscopy. The experimental results show that the position of copper foil into the quartz tube plays a significant role in the Raman features of the graphene, and influences the optical, morphology and surface properties of graphene layers. We believe that these results will be useful for determining the optimum processing conditions of high quality graphene layers at the centimeter and wafer scales.