• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.754-757
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• 2012

In this report, we fabricate the porous graphene films through embossing process and vacuum filtration method and demonstrate their superior electrochemical properties as supercapacitor electrode materials. Insertion/removal of polystyrene nanoparticles between the graphene sheets allows to provide pore structures, leading to the effective prevention of restacking in graphene films. As-prepared porous graphene films have a large surface area, a bicontinuous porous structures, high electrical conductivity, and excellent mechanical integrity. The electrochemical properties of the porous graphene films as electrode materials of supercapacitor are investigated by using aqueous $H_2SO_4$ and ionic liquid solution under three-electrode system. The porous graphene films exhibit a high specific capacitance (284.5 F/g), which is two-fold higher than that of packing graphene films (138.9 F/g). In addition, the rate capability (98.7% retention) and long-term cycling stability (97.2%) for the porous graphene films are significantly enhanced, due to the facilitated ion mobility between the graphene layers.

• Particle and aerosol research
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• v.15 no.4
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• pp.183-190
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• 2019

Here, we introduce porous graphene balls (PGB) showing superior electrochemical properties as supercapacitor electrode materials. PGB was fabricated via activation of graphene oxides (GO) by H₂O₂ and aerosol spray drying in series. Effect of activation on the morphology, specific surface area, pore volume, and electrochemical properties were investigated. As-prepared PGB showed spherical morphology containing pores, which lead to the effective prevention of restacking in graphene sheets. It also exhibited a large surface area, unique porous structures, and high electrical conductivity. The electrochemical properties of the PGB as electrode materials of supercapacitor are investigated by using aqueous KOH under symmetric two-electrode system. The highest specific capacitance of PGB was 279 F/g at 0.1 A/g. In addition, the high rate capability (93.8% retention) and long-term cycling stability (92.2%) of the PGB were found due to the facilitated ion mobility between the porous graphene layers.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.23-28
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• 2019

We report a supercapacitor cable, which consists of three-dimensional (3D) porous graphene coated onto the surface of carbon thread. The 3D porous framework of graphene was constructed by microwave-activated process using a graphene oxide-coated carbon thread. The use of microwave irradiation enabled to convert graphene oxide into reduced graphene oxide without any reducing agents and activate graphene sheets into exfoliated and porous graphene sheets. Combining two wire electrodes with a polymer gel electrolyte successfully completed supercapacitor device in a form of cable construction. The supercapacitor cables were highly flexible, and thus can be transformed into various shapes of devices and be integrated into textile items. A high area-capacitance of 38.1 mF/cm was obtained at a scan rate of 10 mV/s. This capacitance was retained 88% of its original value at 500 mV/s. The cycle life was also demonstrated by repeating a charge/discharge process during 10,000 cycles even under bent states, showing a high capacitance retention of 96.5%.

• Carbon letters
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• v.22
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• pp.1-13
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• 2017

Porous materials play a vital role in science and technology. The ability to control their pore structures at the atomic, molecular, and nanometer scales enable interactions with atoms, ions and molecules to occur throughout the bulk of the material, for practical applications. Three-dimensional (3D) porous carbon-based materials (e.g., graphene aerogels/hydrogels, sponges and foams) made of graphene or graphene oxide-based networks have attracted considerable attention because they offer low density, high porosity, large surface area, excellent electrical conductivity and stable mechanical properties. Water pollution and associated environmental issues have become a hot topic in recent years. Rapid industrialization has led to a massive increase in the amount of wastewater that industries discharge into the environment. Water pollution is caused by oil spills, heavy metals, dyes, and organic compounds released by industry, as well as via unpredictable accidents. In addition, water pollution is also caused by radionuclides released by nuclear disasters or leakage. This review presents an overview of the state-of-the-art synthesis methodologies of 3D porous graphene materials and highlights their synthesis for environmental applications. The various synthetic methods used to prepare these 3D materials are discussed, particularly template-free self-assembly methods, and template-directed methods. Some key results are summarized, where 3D graphene materials have been used for the adsorption of dyes, heavy metals, and radioactive materials from polluted environments.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.658-658
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• 2013

Graphene is an attractive material for various device applications due to great electrical properties and chemical properties. However, lack of band gap is significant hurdle of graphene for future electrical device applications. In the past few years, several methods have been attempted to open and tune a band gap of graphene. For example, researchers try to fabricate graphene nanoribbon (GNR) using various templates or unzip the carbon nanotubes itself. However, these methods generate small driving currents or transconductances because of the large amount of scattering source at edge of GNRs. At 2009, Bai et al. introduced graphene nanomesh (GNM) structures which can open the band gap of large area graphene at room temperature with high current. However, this method is complex and only small area is possible. For practical applications, it needs more simple and large scale process. Herein, we introduce a photosensitive graphene device fabrication using CdSe QD coated nano-porous graphene (NPG). In our experiment, NPG was fabricated by thin film anodic aluminum oxide (AAO) film as an etching mask. First of all, we transfer the AAO on the graphene. And then, we etch the graphene using O2 reactive ion etching (RIE). Finally, we fabricate graphene device thorough photolithography process. We can control the length of NPG neckwidth from AAO pore widening time and RIE etching time. And we can increase size of NPG as large as 2 $cm^2$. Thin CdSe QD layer was deposited by spin coatingprocess. We carried out NPG structure by using field emission scanning electron microscopy (FE-SEM). And device measurements were done by Keithley 4200 SCS with 532 nm laser beam (5 mW) irradiation.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.105-109
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• 2018

We studied graphene synthesis to porous Cu to improve the characteristics of carbon dioxide reduction of cu. Cu powders were formed through Thermal Chemical Vapor Deposition(TCVD) to Porous Cu/Graphene structures synthesized with graphene. As a result of electrochemical experiments using a 0.1 M $KHCO_3$ electrolyte at an applied potential of -1.0 V to -1.4 V, the current density of Porous Cu/Graphene was 1.8 times higher than that of Porous Cu. As a result of evaluating the product, CO and $H_2$ were generated to Porous Cu electrode. On the other hand, the product of porous Cu/Graphene produced CO, $CH_4$ and $C_2H_4$. It is considered that the graphene causes longer carbon dioxide adsorption time, which means that the intermediates formed during the reaction remain on the electrode surface for a longer time. As a result, it can be concluded that the production reaction of the C2 compound could be continuously performed.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.99-107
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• 2019

Wave propagation analysis of a porous graphene platelet reinforced (GPLR) nanocomposite shell is investigated for the first time. The homogenization of the utilized material is procured by extending the Halpin-Tsai relations for the porous nanocomposite. Both symmetric and asymmetric porosity distributions are regarded in this analysis. The equations of the shell's motion are derived according to Hamilton's principle coupled with the kinematic relations of the first-order shear deformation theory of the shells. The obtained governing equations are considered to be solved via an analytical solution which includes two longitudinal and circumferential wave numbers. The accuracy of the presented formulations is examined by comparing the results of this method with those reported by former authors. The simulations reveal a stiffness decrease in the cases which porosity influences are regarded. Also, one must pay attention to the effects of longitudinal wave number on the wave dispersion curves of the nanocomposite structure.

• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

• Steel and Composite Structures
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• v.43 no.1
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• pp.31-54
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• 2022

This paper is concerned with the buckling behavior of functionally graded graphene reinforced porous nanocomposite beams based on the finite element method (FEM) using two variables trigonometric shear deformation theory. Both Young's modulus and material density of the FGP beam element are simultaneously considered as grading through the thickness of the beam. The finite element approach is developed using a nonlocal strain gradient theory. The governing equations derived here are solved introducing a 3-nodes beam element, and then the critical buckling load is calculated with different porosity distributions and GPL dispersion patterns. After a convergence and validation study to verify the accuracy of the present model, a comprehensive parametric study is carried out, with a particular focus on the effects of weight fraction, distribution pattern of GPL reinforcements on the Buckling behavior of the nanocomposite beam. The effects of various structural parameters such as the dispersion patterns for the graphene and porosity, thickness ratio, boundary conditions, and nonlocal and strain gradient parameters are brought out. The results indicate that porosity distribution and GPL pattern have significant effects on the response of the nanocomposite beams, and the results allows to identify the most effective way to achieve improved buckling behavior of the porous nanocomposite beam.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.404-409
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• 2018

The integration of organic and inorganic building blocks into hierarchical porous architectures makes potentially desirable catalytic material in many catalytic applications due to their combination of dissimilar components and well-constructed reactant transport path. In this study, we prepared the hierarchical porous $Co_3O_4@graphene$ 3D gel by hydrothermal method to achieve high catalytic performance in PET glycolysis reaction. Obtained $Co_3O_4@graphene$ 3D gel consisted of interconnected networks of $Co_3O_4$ and graphene sheets, providing large number of accessible active sites for efficient catalytic reaction. These structural merits from synergistic effect of $Co_3O_4$ and graphene gave a high performance in the PET degradation reaction giving high conversion yield of BHET, fast degradation rate of PET, and remarkable stability.