Method For Production Of Graphene Research Articles

Morphological and Thermal Characterization of Low-Cost Graphene Produced by Electrochemical Exfoliation Method

The low-cost and mass production of graphene has gained importance in recent years. The electrochemical exfoliation method, one of the graphene production methods, is an efficient technique used to obtain low-cost-effective and large quantities of graphene nanosheets. Exfoliation parameters affect the properties of exfoliated graphene nanosheets. In this study, graphene production is fabricated by the method of exfoliation using electrolyte and voltage parameters. For this, a pen tip was used instead of pure platinum, which is very expensive, at the cathode. The structural research was done by X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Fourier Transform Infrared Spectrometer (F-TIR). Morphological analyses were carried out by Scanning Electron Microscopy (SEM). The number of layers and crystallite of graphene layers were estimated. The obtained results were compared with the results of the other similar studies. Analysis results show that low-cost multilayer graphene can be produced by the electrochemical exfoliation method with the electrical parameters.

Introducing graphene‐enhanced technologies to the regulated market to mitigate carbon emissions

AbstractAmbitious net zero carbon emissions goals have been set by various climate change agencies and government officials, including President Biden. One of the most prominent emissions goals aims to reach net zero carbon emissions globally by 2050. Unfortunately, the United States is not on track to achieving this goal and the United Nations has announced that several nations have fallen short of their carbon emissions agreements. Increases in global temperatures, deadly natural disasters, and species extinction have heightened the pressure facing scientists and policymakers to convince nations to stay on course to reach net zero emissions within the next few decades. Last year, the largest contributor to carbon dioxide emissions in the United States was “U.S. motor gasoline and diesel (distillate) fuel consumption” (U.S. Energy Information Administration, Frequently Asked Questions), making it clear that changes must be made in the energy sector to mitigate this. Recent innovations in the battery industry have shown exciting promise for the future of clean energy, though regulatory barriers must be overcome to fully establish these new technologies. One such technology is the graphene‐enhanced lithium‐ion battery which has five times the energy density of regular lithium‐ion batteries due to the high thermal conductivity of graphene. However, graphene is difficult to produce on a large scale, and many investors and stakeholders have hesitated to participate in the graphene supply chain due to the lack of regulation and health and safety information on graphene. The EPA (Environmental Protection Agency), along with other standardization organizations, has worked to understand nanomaterials like graphene over the past decade, but they seem to be behind in producing substantial data on the material's properties. Furthermore, current graphene manufacturers have varying ways of classifying and labeling graphene products, creating additional confusion in the marketplace. To accelerate the process of researching and regulating graphene, the EPA's adherence to predetermined deadlines for the creation of regulations for up‐and‐coming materials must be mandated, a standardized graphene labeling system should be adopted, universities and federal agencies should be incentivized to collaborate on research related to graphene production methods, and a mandatory “battery passport” system should be implemented to ensure the widespread availability of battery information. These recommendations are aimed at increasing trust and collaboration within the graphene industry and standardizing graphene materials to reduce ambiguity within the supply chain. By implementing these policy changes, the use of graphene‐enhanced lithium‐ion batteries in electric vehicles and grid energy storage systems can become more widespread, and allow for higher efficiency. As improvements are made to clean energy alternatives, the use of fossil fuels can be reduced, thus, decreasing overall carbon emissions.

Liquid Phase Graphene Exfoliation with a Vibration-Based Acoustofluidic Effector.

Liquid phase exfoliation (LPE) has emerged as a promising method for the industrial-scale production of graphene. However, one of its critical steps, namely sonication, has faced challenges due to high power consumption and low efficiency, leading to limited applicability in industrial settings. This study introduces a novel, cost-effective microfluidic sonication device designed to significantly reduce power consumption while efficiently assisting the LPE process for graphene production. By coupling a capillary with a buzzer and applying an appropriate electric signal, simulation and particle tracing experiments reveal the generation of robust shear forces resulting from acoustic streaming and cavitation when the capillary end is immersed in the liquid. For the first time, the capillary-based sonication device was effectively utilized for graphene exfoliation in a DMF (N,N-Dimethylformamide) + NaOH liquid phase system. The SEM (Scanning Electron Microscope) and Raman characterization results corroborate the successful exfoliation of 100 nm with thicknesses below 10 nm graphene sheets from graphite flakes using this pioneering device. The values of I2D/IG increase after processing, which suggests the exfoliation of graphite flakes into thinner graphene sheets. The vibration-based acoustofluidic effector represents a versatile and scalable miniature device, capable of being employed individually for small-batch production, thereby optimizing the utilization of raw 2D materials, particularly in experimental scenarios. Alternatively, it holds the potential for large-scale manufacturing through extensive parallelization, offering distinct advantages in terms of cost-efficiency and minimal power consumption.

A Facile and Scalable Fabrication of High-Performance Flexible Laser-Induced-Graphene Micro-Supercapacitors Using Ultrafast Pulse Laser

The rapid growth of wearable and portable electronics has promoted the development of microscale energy storage devices. Among these devices, microsupercapacitors (MSCs) have emerged as promising flexible energy storage devices owing to their high power density, high charge/discharge rate, and long-term cycling stability.[1,2,3] Most synthesis method of graphene electrodes for flexible MSCs rely on complex processes or chemical synthesis routes, such as photolithography, mechanical exfoliation, or chemical and thermal reduction. On the other hand, laser direct writing are a simple, design-flexible, highly scalable, and cost-effective method for graphene production. Here, we developed two types of green flexible microsupercapacitor using femtosecond pulse laser. First, we report a high performance sticker-type flexible microsupercapacitor using highly swollen reduced-graphene oxide electrodes fabricated by an ultrashort pulse laser.[4] Second, we demonstrate the direct fabrication of highly conductive, intrinsically flexible, and green microelectrodes from naturally fallen leaves in ambient air using femtosecond laser pulses without any additional materials.[5] Both types of MSCs not only showed excellent electrochemical performance, but were confirmed to work as a power supply for various applications such as LED and thermometer. Therefore, our flexible microsupercapacitors can be widely applied as energy-storage devices for flexible/wearable electronics.

An integrated method for massive production of graphene from bituminous coal via ultrasonication-assisted emulsion formation

ABSTRACT Up to date, various methods of graphene production have been rapidly developed for a range of applications. However, large-scale production with low cost is still desired. The chemical exfoliation route is expected to be the best alternative although there are still many aspects that can be further improved, for example, raw materials. Instead of using graphite, bituminous coal is a better candidate to be used as the raw material for synthesizing graphene because it is cheap and abundant. Moreover, the use of coal is only limited to the electricity purpose. In this study, a new chemical exfoliation method followed by thermal reduction was explored to fabricate graphene from bituminous coal. This method involves ultrasonication-assisted emulsion formation for separation to remove the remaining residual coal. As a result, 0.9 wt% of bituminous coal could be exfoliated with graphene. Based on several characterization techniques, coal-derived graphene produced from this integrated method has competitive qualities compared to graphite-derived graphene.

Influence of C=O groups on the optical extinction coefficient of graphene exfoliated in liquid phase

Liquid phase exfoliation of graphite is currently one of the most promising graphene production methods at large scale. For this reason, an accurate calculation of the concentration in graphene dispersions is important for standardization and commercialization. Here, graphene dispersions, at high concentrations, were produced by electrochemical exfoliation. Furthermore, a cleaner methodology to obtain graphene oxide by electrochemical exfoliation at high acid concentrations was implemented. The absorption coefficient for graphene and graphene oxide was determined in the optical range (α 660 nm = 1414 (±3%) ml mg−1 m−1 and α 660 nm = 648 (±7%) ml mg−1 m−1, respectively) with an exponential dependence with the wavelength. The difference in α for both materials is attributed to an increased presence of C=O groups as evidenced by Fourier transform infrared spectroscopy (FTIR), UV–vis and Raman spectroscopy, as well as, in the calculation of the optical extinction coefficient and optical band-gap via Tauc-plots.

3D Structured Graphene Anodes for Alkali Metal Ion Storage Applications

Electrochemical exfoliation of graphite into graphene has emerged as a promising manufacturing method for the fast production of graphene at a low cost. We will first discuss our recent efforts to understand the electrochemical exfoliation process of graphite under various electrolyte conditions to control the structures of graphene products.1 Then, we will introduce the stacking and defect engineering processes to assemble 3D structured graphene electrodes.2, 3 The 3D graphene anodes delivered enhanced capacities for Li-, Na-, K-ion storage due to the effective utilization of surface defects. In particular, the 3D graphene anodes can exhibit superior charge-storage performance under extremely low-temperature conditions. We reveal that the role of the surface-charge storage mechanism in improving the charge storage performance under low-temperature conditions.References Lee, H.; Choi, J. I.; Park, J.; Jang, S. S.; Lee, S. W. Role of anions on electrochemical exfoliation of graphite into graphene in aqueous acids. Carbon 2020, 167, 816-825.Lee, B.; Kim, M.; Kim, S.; Nanda, J.; Kwon, S. J.; Jang, H. D.; Mitlin, D.; Lee, S. W. High Capacity Adsorption—Dominated Potassium and Sodium Ion Storage in Activated Crumpled Graphene. Adv. Energy Mater. 2020, 10, 1903280.Lee, M. J.; Lee, K.; Lim, J.; Li, M.; Noda, S.; Kwon, S. J.; DeMattia, B.; Lee, B.; Lee, S. W. Outstanding Low-Temperature Performance of Structure-Controlled Graphene Anode Based on Surface-Controlled Charge Storage Mechanism. Adv. Funct. Mater. 2021, 31, 2009397.

Graphene exfoliation with supercritical fluids

Graphene is an unconventional material with a two-dimensional hexagonal crystalline array of elemental carbon atoms and outstanding properties; accordingly, a desirable objective in the line of research of graphene is the development of novel and more productive methods of synthesis, validating its properties and applications. In our exploratory research, we have effectively exfoliated graphene from graphite using supercritical fluids (water, ethanol and carbon dioxide). The exfoliated graphene was properly characterized; via scanning electron microscopy, the morphology of graphene was observed; Raman spectra confirmed the exfoliation of graphene depicting the characteristic shift towards smaller Raman number in the 2D band (2676 cm−1) compared to that of graphite (≈ 2700 cm−1); transmission electron microscopy analysis exhibited the crystalline structure of graphene attesting also the expected transparency of exfoliated layers. Graphene exfoliation from graphite by supercritical fluids promises to be a simple large-scale method for graphene production.

Evidence of graphite blister evolution during the anion de-intercalation process in the cathodic regime

Ion intercalation inside graphite crystal is a well-established method for graphene production. Pure acid electrolytes swell the stratified crystal structure and a gentle sonication disperses graphene flakes inside the solution. In view of a better environment-friendly graphite delamination procedure, diluted electrolytes can represent a viable option. Unfortunately, the presence of solvated ions between graphite planes induces oxidation of carbon atoms and the following development of gases in the buried layers of the crystal. Being not permeable, graphite entraps the gases that deform the crystal by producing characteristic bubbles called blisters. The latter represent a detriment of the original specimen and influence the quality of the produced graphene flakes.Here, we will address key properties of blister formation and growth by proving, in particular, that blisters evolve when the applied electrochemical potential value is reduced (cathodic regime), i.e. after the intercalation, conversely to what has been believed for long time. This finding requires a refinement of the current anion intercalation interpretative model.

Seed-Assisted Synthesis of Graphene Films on Insulating Substrate.

Synthesizing graphene at a large-scale and of high quality on insulating substrate is a prerequisite for graphene applications in electronic devices. Typically, graphene is synthesized and then transferred to the proper substrate for subsequent device preparation. However, the complicated and skilled transfer process involves some issues such as wrinkles, residual contamination and breakage of graphene films, which will greatly degrade its performance. Direct synthesis of graphene on insulating substrates without a transfer process is highly desirable for device preparation. Here, we report a simple, transfer-free method to synthesize graphene directly on insulating substrates (SiO2/Si, quartz) by using a Cu layer, graphene oxide and Poly (vinyl alcohol) as the catalyst, seeds and carbon sources, respectively. Atomic force microscope (AFM), scanning electronic microscope (SEM) and Raman spectroscopy are used to characterize the interface of insulating substrate and graphene. The graphene films directly grown on quartz glass can attain a high transmittance of 92.8% and a low sheet resistance of 620 Ω/square. The growth mechanism is also revealed. This approach provides a highly efficient method for the direct production of graphene on insulating substrates.

CVD-graphene/graphene flakes dual-films as advanced DSSC counter electrodes

The use of graphene‐based electrodes is burgeoning in a wide range of applications, including solar cells, light emitting diodes, touch screens, field‐effect transistors, photodetectors, sensors and energy storage systems. The success of such electrodes strongly depends on the implementation of effective production and processing methods for graphene. In this work, we take advantage of two different graphene production methods to design an advanced, conductive oxide- and platinum-free, graphene-based counter electrode for dye-sensitized solar cells (DSSCs). In particular, we exploit the combination of a graphene film, produced by chemical vapor deposition (CVD) (CVD-graphene), with few-layer graphene (FLG) flakes, produced by liquid phase exfoliation. The CVD-graphene is used as charge collector, while the FLG flakes, deposited atop by spray coating, act as catalyst for the reduction of the electrolyte redox couple (i.e. - and Co+2/+3). The as-produced counter electrodes are tested in both - and Co+2/+3-based semitransparent DSSCs, showing power conversion efficiencies of 2.1% and 5.09%, respectively, under 1 SUN illumination. At 0.1 SUN, Co+2/+3-based DSSCs achieve a power conversion efficiency as high as 6.87%. Our results demonstrate that the electrical, optical, chemical and catalytic properties of graphene-based dual films, designed by combining CVD-graphene and FLG flakes, are effective alternatives to FTO/Pt counter electrodes for DSSCs for both outdoor and indoor applications.

Water Dispersible Few-Layer Graphene Stabilized by a Novel Pyrene Derivative at Micromolar Concentration.

The search for graphene or few-layer graphene production methods that are simple, allow mass production, and yield good quality material continues to provoke intense investigation. The present work contributes to this investigation through the study of the aqueous exfoliation of four types of graphene sources, which are namely graphite and graphite nanoflakes with different morphologies and geographical origins. The exfoliation was achieved in an aqueous solution of a soluble pyrene derivative that was synthesized to achieve maximum interaction with the graphene surface at low concentration (5 × 10−5 M). The yield of bilayer and few-layer graphene obtained was quantified by Raman spectroscopic analysis, and the adsorption of the pyrene derivative on the graphene surface was studied by thermogravimetric analysis and X-ray diffraction. The whole procedure was rationalized with the help of molecular modeling.

Adsorption of graphene to metal (111) surfaces using the exchange-hole dipole moment model

Graphene has a unique electronic structure and excellent tribological properties. A promising method for graphene production involves depositing vaporized carbon on metal substrates, which can also be used to modify graphene's electronic structure through charge transfer. In this work, graphene adsorption on the (111) surface of seven metals (Al, Cu, Ag, Au, Ni, Pd, and Pt) is investigated computationally using density-functional theory with the exchange-hole dipole moment (XDM) dispersion correction. Two distinct graphene-metal orientations, corresponding to 0∘ and 30∘ relative rotation of the graphene layer, are considered to investigate how lattice mismatch affects adsorption. Our results reproduce reference data from the random-phase approximation more closely than other dispersion-corrected density functionals, confirming that XDM is an excellent method for surface chemistry. The rotational orientation of graphene is found to strongly affect its interaction with the substrate. There is an energetic drive for graphene to align with the metal lattice, particularly for Pd and Pt, which causes the formation of multiple Moiré patterns, in agreement with experimental observations.

Graphene Growth by Conversion of Aromatic Self‐Assembled Monolayers

AbstractDespite present diversity of graphene production methods there is still a high demand for improvement of the existing production schemes or development of new. Here a method is reviewed to produce graphene employing aromatic self‐assembled monolayers (SAMs) as molecular precursors. This method is based on electron irradiation induced crosslinking of aromatic SAMs resulting in their conversion into carbon nanomembranes (CNMs) with high thermal stability and subsequent pyrolysis of CNMs into graphene in vacuum or in the inert atmosphere. Depending on the production conditions, such as chemical structure of molecular precursors, irradiation and annealing parameters, various properties of the produced graphene sheets including shape, crystallinity, thickness, optical properties and electric transport can be adjusted. The assembly of CNM/graphene van der Waals heterostructures opens a flexible route to non‐destructive chemical functionalization of graphene for a variety of applications in electronic and photonic devices.

Perylene tetracarboxylate surfactant assisted liquid phase exfoliation of graphite into graphene nanosheets with facile re-dispersibility in aqueous/organic polar solvents

Liquid phase exfoliation (LPE) is a promising method for graphene production particularly in terms of cost effectiveness and scale up. Nonetheless, it is still challenging to synchronize prime goals of high quality, good yield, large sheet size, stable long term storage and low cost eco-friendly processing. We present a simple and inexpensive green route for large scale production of exfoliated graphene dispersions exploiting the non-covalent surface chemistry between graphene and perylene tetracarboxylate (PTCA) aromatic semiconducting surfactant. Direct sonication of graphite flakes in aqueous PTCA solutions produced high yield of single and few-layer graphene sheets with minimal basal plane defects as revealed by XPS, Raman and FTIR spectroscopy. Uniquely for LPE protocol, the lateral graphene flake dimensions extended upto 10–12 μm range. The exfoliated dispersions exhibited high colloidal stability with shelf-life exceeding a year. Facile re-dispersibility of the dried graphene/PTCA powders was observed in water as well as many polar organic solvents. Significantly, pure aromatic semiconducting nature of surfactant without dielectric moiety ensures tight electrical contact among graphene sheets in thin films. The approach exploiting the simple molecular design of aromatic charged surfactants for graphene exfoliation holds a great prospect for solution processed graphene based nanomaterials and devices.

Liquid-Phase Exfoliation of Few-Layer Graphene and Effect of Sonication Time on Concentration of Produced Few Layer Graphene

Although graphene has been produced by various methods at lab scale, however, its cost effective mass production method is still a challenge. Graphene has been produced by liquid phase exfoliation, which is the most probable method for commercial production of graphene for various industrial applications.This paper reports high concentration production of few-layer graphene in DMSO (dimethyl sulfoxide) as solvent through liquid phase exfoliation assisted with sonication. The temperature was kept below 30oC. SEM, AFM, and XRD were used to characterize the produced graphene. SEM results confirm the production of few-layer graphene. EDX analysis shows that the graphene surface is free from oxides and impurities. AFM results also confirm the production of few-layer graphene. The UV-visible spectrophotometer was used to determine the concentration of the produced graphene, and the investigations demonstrate that the graphene production was increased by increasing the sonication time. There exist a linear relationship between the amount of produced graphene and sonication time for supplying energy during sonication.

Sucrose-mediated mechanical exfoliation of graphite: a green method for the large scale production of graphene and its application in catalytic reduction of 4-nitrophenol

A simple and green method for the large scale production of graphene by ball-milling of graphite with sucrose is exploited here.

Safe growth of graphene from non-flammable gas mixtures via chemical vapor deposition

Chemical vapor deposition has emerged as the most promising technique for the growth of graphene. However, most reports of this technique use either flammable or explosive gases, which bring safety concerns and extra costs to manage risk factors. In this article, we demonstrate that continuous monolayer graphene can be synthesized via chemical vapor deposition technique on Cu foils using industrially safe gas mixtures. Important factors, including the appropriate ratio of hydrogen flow and carbon precursor, pressure, and growth time are considered to obtain graphene films. Optical measurements and electrical transport measurements indicate graphene films are with comparable quality to other reports. Such continuous large area graphene can be synthesized under non-flammable and non-explosive conditions, which opens a safe and economical method for mass production of graphene. It is thereby beneficial for integration of graphene into semiconductor electronics.

Green reduction of graphene oxide using alanine

There remains a real need for the easy, eco-friendly and scalable preparation method of graphene due to various potential applications. Chemical reduction is the most versatile method for the large scale production of graphene. Here we report the operating conditions for a one-step, economical and green synthesis method for the reduction of graphene oxide using a biomolecule (alanine). Graphene oxide was produced by the oxidation and exfoliation of natural graphite flake with strong oxidants using Hummers method (Hummers and Offeman, 1958), but the method was revised in our laboratory to set up a safe and environmentally friendly route. The reduction of graphene oxide was investigated using alanine at various operating conditions in order to set up optimum conditions (treatment time, temperature and concentration of the reagent). Samples have been characterized by using UV–Visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction analysis.

Scalable Conversion of Carbon Dioxide into Graphene for Electrochemical Energy Storage

Graphene materials are regarded as one promising candidate for next-generation electrochemical energy storage devices due to its unique properties, such as high specific surface area and electrical conductivity. However, most of the up-to-date methodologies for producing graphene, such as chemical vapor deposition, mechanical exfoliation and reduction of graphite oxide, involve several severe drawbacks including heavy ion pollution, low yield and labor-intensive processes, which raise the cost and limit the scalability of graphene production. Therefore, a facile and cost-saving pathway for high-quality graphene synthesis is urgently needed. Combustion of fossil oil still represents a major energy source for electricity generation around the world, which releases a tremendous amount of CO2 to cause detrimental global warming. As a result, a prospective method for graphene production is to use the available CO2 as feedstock gas. But due to the inherent chemical stability of C=O bond, it is a great challenge to reduce CO2 into carbon materials by conventional techniques. It is well-established that magnesiothermic reaction is capable of dissociating strong chemical bonds, which offers a potential way for effective utilization of CO2. Herein, we present an ultra-fast magnesiothermic reaction to fabricate few-layer graphene with highly developed mesoporosity from CO2 and magnesium/magnesium oxide mixture. It is demonstrated that magnesium oxide acts as the crucial template to guide graphene formation and provide mesopores after acid rising. The ordered mesoporous graphene exhibits a high specific surface area of 709 m2 g-1 and a narrow pore size distribution around 4 nm. We further confirm its excellent electrochemical performance as supercapacitor electrodes. In IL electrolyte, the specific capacitance of MSG is as high as 260 F g-1 at 2 A g-1, corresponding to an energy density of 135.6 Wh kg-1, and can still maintain 173 F g-1 at an ultra-high rate of 100 A g-1. This excellent rate capability performance gives birth to an unprecedented power density of 7684 kW kg-1. Moreover, the electrochemical stability is demonstrated by a high capacitance retention of 90% after 1 million cycles of rapid charge/discharge at 100 A g-1. We believe our present work will give a new insight into the production of high-quality graphene materials. Fig. 1 Ordered mesoporous graphene prepared by ultra-fast magnesiothermic reaction Figure 1