Amount Of Oxygen Functional Groups Research Articles

The influence of the functional group on activated carbon for acetone adsorption property by molecular simulation study

In this paper, different types and amounts of oxygen functional groups are inserted in graphitic slit pores to investigate the individual effect of each factor, which aims to clarify the effects of functional groups in activated carbon on acetone adsorption based on molecular simulation. Adsorption isotherms of acetone are then calculated by using Grand Canonical Monte Carlo (GCMC) simulation. Simulation results show that acetone adsorption capacity is increased at low fugacity after inserting oxygen-containing functional groups, however, equilibrium adsorption capacity is decreased. Along with the increase of amounts of functional group, the acetone adsorption loading is not always increased due to the reduction of available adsorption sites on pore wall. Also, it is concluded that trace acetone (10ppmv) is adsorbed mainly in 1.0 nm pore, in which the oxygen content is 5 wt% and the functional group planted in is hydroxyl that is the most beneficial one to trace acetone adsorption.

Oxygen functionalization of MWCNTs in RF-dielectric barrier discharge Ar/O2 plasma

The oxygenation of multi-wall carbon nanotubes (MWCNTs) was performed via a radio frequency dielectric barrier discharge (RF-DBD) in an Ar/ plasma mixture. The relative intensity of the Ar/ plasma species was characterized by optical emission spectroscopy (OES). The effects of treatment time, RF power and oxygen gas percentage on the chemical composition and surface morphology of MWCNTs were investigated by means of x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). The results of FTIR and XPS revealed the presence of oxygen-containing functional groups on the MWCNTs treated in an Ar/ plasma at an RF power of 50 W and pressure of 400 Pa. The amount of oxygen functional groups (C=O, C–O, and O–COO) also increased by increasing treatment time up to 6 min, but slightly decreased when treatment time was increased by 10 min. The increase of oxygen gas percentage in the plasma mixture does not affect the oxygen content in the treated MWCNTs. Meanwhile, MWCNTs treated at high power (80 W) showed a reduction in oxygen functional groups in comparison with low RF power conditions. The Raman analysis was consistent with the XPS and FTIR results. The integrity of the nanotube patterns also remained damaged as observed by FE-SEM images. The MWCNTs treated in RF-DBD using the Ar/ plasma mixture showed improved dispersibility in deionized water. A correlation between the OES data and the observed surface characterization for an improved understanding of the functionalization of MWCNTs in Ar/ plasma was presented.

Deep study on effects of activated carbon’s oxygen functional groups for elemental mercury adsorption using temperature programmed desorption method

Oxygen functional groups play an important role in elemental mercury adsorption by activated carbon (AC). However, the adsorption mechanism of oxygen functional groups is unclear. This study investigated the effects of oxygen functional groups on elemental mercury adsorption using temperature programmed desorption method. Nitric acid treatment, non-thermal plasma treatment, and heat treatment in nitrogen or carbon dioxide were used to modify AC’s oxygen functional groups and pore structures. Base–acid titration experiments were conducted to calculate the amount of oxygen functional groups of samples. Mercury removal efficiency tests and temperature programmed desorption experiments of AC were carried out in a bench-scale quartz reactor. The results suggested that the mercury removal performance of AC was determined by the comprehensive effects of surface area, carbonyl group and ester group, and each of them had different influences on mercury adsorption at different temperatures. Physisorption which related with surface area only occurred in the temperature range from 30°C to 130°C, and it was inhibited by increasing temperature; while carbonyl group and ester group could capture mercury in the temperature range from 30°C to 210°C. However, increasing temperature could inhibit the mercury adsorption by carbonyl group in the temperature range of 130–210°C, and the ester group dominated mercury adsorption at 210°C. In addition, carbonyl group and ester group had different priority levels for mercury adsorption, active sites related with ester group had the highest priority of capturing mercury, and active sites in correlation with carbonyl group was the second, while active sites corresponding with physisorption was the last one.

Origin of extraordinary luminescence shift in graphene quantum dots with varying excitation energy: An experimental evidence of localized sp2 carbon subdomain

We report the extraordinary photoluminescence (PL) behavior of high-quality graphene quantum dots (GQDs) prepared with a graphite intercalation compound method: the alternating PL peak shifts (redshift-blueshift-redshift) with increasing the excitation wavelength. The PL peak position is redshift in the excitation wavelength range 250–270 nm, subsequently blueshift in 270–290 nm, and again redshift in the range 290–330 nm. This unconventional optical response of the GQDs is attributed to two types of energy states: intrinsic states formed by localized sp2 carbon subdomains and extrinsic states created by various oxygen-functional groups. The PL behavior of GQDs shows different tendencies according to the size and amount of oxygen-functional groups. Furthermore, since the extrinsic states of GQDs can be inactivated under acidic condition, its extraordinary PL behavior of high-quality GQDs with varying excitation wavelength largely recedes. On the other hand, we clearly observed these alternating PL shift behaviors when localized sp2 carbon subdomains with intrinsic emission are artificially formed by reducing oxygen-functional groups in graphene oxide quantum dots, which have mostly the extrinsic PL originated from the energy states of various oxygen-functional groups. The results offer experimental evidence for the existence of localized sp2 carbon subdomains and provide key information that clarifies the electronic structure of GQDs and their derivatives.

Carbon-based cathode as an electron donor driving direct bioelectrochemical denitrification in biofilm-electrode reactors: Role of oxygen functional groups

Carbon-based cathodes are widely used in the biofilm-electrode reactor (BER) favoring a direct bioelectrochemical denitrification. However, little is known about how the surface chemistry of carbon affects the formation of bacterial biofilms on the electrode surface, which is fundamental to the functioning of BER for the nitrate removal. In the present study, graphite granules used in the three-dimension BER were oxidized by different methods, such as treatment with HCl, H2O2, HNO3 and HNO3+heat, providing the surface oxygen content as 1.98, 4.10, 7.70 and 11.54 at %, respectively. Likewise, the denitrifying BER equipped with the HNO3+heat-treated cathode exhibited a reaction rate of 27.36 mg NO3−-N L−1 d−1, exceeding 19.96, 14.82 and 13.93 mg NO3−-N L−1 d−1 obtained from the BERs with HNO3, H2O2- and HCl-treated cathodes, respectively. It was revealed that the oxidation treatment led to the increase in the amounts of oxygen functional groups (largely in the form of carboxyl), which were beneficial for the growth of metabolically active bacteria and thus the increased bioelectrochemical reaction kinetics. Bacterial analysis showed that the cathode-driven autotrophic denitrifiers were dominantly represented by Thiobacillus and Sulfurimonas, which displayed the highest abundance on the cathode pretreated with a hot and refluxed HNO3 solution.

Secondary Interactions of Graphene Oxide on Liquid Crystal Formation and Stability

Graphene oxide liquid crystals (GO LC) prove their potential usefulness in a new design of carbon scaffold composites with ordered structures from nano to macroscale. This paper highlights the degree of GO functionalization as a notable influencing factor on GO LC formation. The large amount of oxygen functional groups, which cause secondary interactions between GOs, decrease the critical concentration for the phase transitions from isotropic to biphasic to nematic phases. In the biphasic state where isotropic and anisotropic phases coexist, highly oxidized GO sheets spontaneously develop LC phases among themselves. Furthermore, the strong hydrogen bonding networks between GO sheets govern the stabilization of the GO aqueous dispersion for a long period. This unique behavior can be used to design GO‐based architecture with controllable density and ordering.

The Flotation Characteristics of Lignite After Low-Temperature Pyrolysis Pretreatment

The basic property of the lignite and its pyrolysis products were studied by proximate and ultimate analysis. The effect of collector types on the flotation performance of semi-coke was studied. The results showed that collector consumption of semi-coke was much higher when compared with coking coals due to the larger surface area and a large amount of oxygen functional groups. The semi-coke exhibited a good flotation performance with the emulsified collector at an economical collector consumption.

Laser reduced graphene for supercapacitor applications

Abstract Graphene was prepared by excimer laser irradiation reduction of graphite oxide dissolved in an aqueous solution at different laser energies and irradiation time. The morphologies and structure of the laser reduced graphene were characterized using scanning electron microscopy, low angle X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. The XRD results confirm that the deoxygenation of the graphite oxide sheets occurred almost completely for all laser irradiation conditions used. The graphene fabricated by laser irradiation reduction appears to be randomly aggregated, crumpled, disordered and small sheet solid material. The total amount of oxygen functional groups reduced significantly and the CC/CO intensity ratio increased, however, the atomic percentages of the C O double bond were increased after laser reduction. The laser reduced graphene was used as the electrode active material for supercapacitors and its specific capacitance was evaluated in a two electrode cell in either a 0.5 M Na 2 SO 4 aqueous or a 1 M Tetraethylammoniumtetrafluoroborate acetonitrile based electrolyte. The specific capacitance of the laser fabricated graphene was found to depend on the energy and irradiation time of the laser. The highest specific capacitance was determined to be 141 F/g at 1.04 A/g and 84 F/g at 1.46 A/g in the aqueous and ACN electrolytes, respectively.

Facile electrochemical approach for the production of graphite oxide with tunable chemistry

Reproducible and in-depth studies of the electrochemical graphite intercalation and oxidation processes were carried out with the use of an electrochemical Tee-cell setup. The electrochemical method allowed simpler and greater controllability over the level of oxidation/functionalization, relative to the commonly employed chemical oxidation approach (e.g. the modified Hummers method). Extensive characterization was carried out to understand the properties of the electrochemically-derived graphite oxide (EGrO), and it was found that the abundance of each functionality was highly dependent on the electrochemical reaction time or the concentration of the electrolyte (perchloric acid) employed. Notably, the amount of oxygen functional groups on EGrO could be as high as 30 wt%, but the degree of oxidation did not proceed beyond the generation of carbonyl species. The controllable oxidation level of the EGrO makes it an attractive precursor for many applications, such as electronics and nanocomposites.

Poly(methyl methacrylate) nanocomposites based on graphene oxide: a comparative investigation of the effects of surface chemistry on properties and foaming behavior

The effects of oxygen functional groups and alkyl chains at the surface of graphene oxide (GO) on the thermal stability, mechanical properties and foaming behavior of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. Alkyl‐functionalized GO (GO‐ODA) was prepared by grafting octadecylamine (ODA) on the surface of GO. PMMA/GO and PMMA/GO‐ODA nanocomposite were obtained by solution blending and were foamed using supercritical carbon dioxide (scCO2). GO‐ODA, with the presence of alkyl chains, showed a better dispersion capability in PMMA matrix than GO with a large amount of oxygen functional groups. In addition, the good dispersion capability increased thermal stability and mechanical strength. In comparison with PMMA/GO samples foamed at 70 °C, PMMA/GO‐ODA nanocomposite foams displayed improved cell structures with higher cell density, smaller cell size and more homogeneous cell size distribution, which results from the strong heterogeneous nucleation due to alkyl chains on the GO surface. The foaming behaviors became more complicated at 80 °C as the GO might be intercalated and exfoliated with the aid of scCO2, thus further enhancing the heterogeneous nucleation during the foaming process. The results indicated that the surface chemistry of GO was closely related to the properties and foaming behavior of the nanocomposites. © 2016 Society of Chemical Industry

Improvements In Electronic Structure And Properties Of Graphene Derivatives

This article focuses on the reduction of graphene oxides using different reductants and conditions systematically varying the chemical and physical structure, surface topography and chemistry and film thickness of reduced graphene oxide (rGO) films, with a focus on how these influence the property of most interest: electrical conductivity. The reduction process restores graphene oxide to a graphene-like structure, improving electrical conductivity while creating changes such as increased roughness, film thickness and new surface functionality. Films with smooth surfaces and minimal thicknesses have been shown to possess higher electrical conductivity. There have been minor changes in d-spacing and improvements in crystal perfection and orientation could be concluded from XRD patterns. Through XPS analysis, a significant decrease in the amount of oxygen functional groups at the surface has been noticed as the films get thinned. Copyright © 2016 VBRI Press.

Persulfate Chemical Functionalization of Carbon Nanotubes and Associated Adsorption Behavior in Aqueous Phase

The chemical functionalization of carbon nanotubes (CNTs) using sodium persulfate (SPS) oxidation was designed to improve their dispersion stability in water. The test results indicated that base activated SPS oxidation of CNTs (BSPS/CNTs) adds a significant amount of oxygen functional groups to the surface of CNTs. The BSPS/CNTs dispersion is dependent on a solution within the pH range of 5–12. Experimental results obtained by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that CNTs were successfully modified and the carboxylic functional groups (e.g., –COO–Na+ or –COO–H+) were created. The BSPS/CNTs, which carry negative charges, enhance the dispersion characteristics of CNTs. The BSPS/CNTs adsorption capacities of inorganic ions (e.g., copper ion) and organic compounds (e.g., benzene) were higher than those obtained by raw CNTs mainly due to enhanced CNTs dispersion. Furthermore, Langmuir and Freundlich adsorption models were applied to examine both raw CNTs a...

The properties of Chinese typical brown coal water slurries

ABSTRACTEight typical Chinese brown coals were evaluated for their potential as coal water slurries (CWSs). The solid ratios and stability of brown coal water slurries were studied and compared with bituminous coal slurries. Results showed the amounts of oxygen functional groups in brown coals are much higher than that in bituminous. Thus, solid ratios at fixed viscosity for brown coal slurries are about 46–55%wt, much lower than those for the bituminous samples that are about 65%wt. Most slurries of brown coals exhibit good stability. Moreover, additives never universally improve slurry ability and stability simultaneously.

Enhanced electrochemical sensing of nitroaromatic compounds based on hydroxyl modified carbon submicroparticles

To explore the active sites for detection of nitroaromatic compounds and improve the sensing performance of carbon based materials, the commercial carbon nanoparticles (CNPs), nitric acid pre-oxidized carbon nanoparticles (OCNPs) and hydroxyl-rich carbon submicrospheres (HCSs) were systematically investigated by transmission electron microscopy, infrared spectroscopy, X-ray photoelectron spectra and electrochemical tests. OCNPs, prepared from CNPs by HNO3 oxidation, contain amounts of oxygen functional groups (OFG) including –COOH, –OH, CO and so on. HCSs, prepared by the green and facile hydrothermal carbonization of glucose, possess the highest loading of hydroxyl groups (approximately 80% of total surface oxygen-containing groups) among these carbon materials. The HCSs modified electrode exhibits the highest current response to nitrobenzene (NB), accompanied by a favorably low background current which is only 30% of that for OCNPs. The excellent sensing performance is attributed to the abundant hydroxyl groups, which facilitate the formation of H-bonding and charge-transfer interaction between electron-donating hydroxyl groups on HCSs and electron-deficiency nitroaromatic molecules. The further investigation by square wave voltammetry indicates that the HCSs modified electrode exhibits a series of well-defined current peaks for NB, dinitrobenzene (DNB) and trinitrobenzene (TNB) with high sensitivity (>6nAμg−1L) and low detection limit (0.88∼1.8μgL−1). Moreover, the proposed sensor exhibits high reproducibility, satisfactory storage stability and good anti-interference ability.

Effect of Edge-Carboxylation in Graphene Nanoplatelets on the Performance of Electrochemical Energy Storage

Graphene is considered prospective electrode materials for the electrochemical supercapacitor due to their higher surface area, good electronic conductivity, high chemical stability, and wide operating temperature range. The hetero-atom doping and surface functionalization of graphene are also advantageous to enhance the electrochemical active surface area, thermal and electronic conductivity, wettability and ion transport, and stability. The edge-carboxylated graphene nanoplatelets have been used as oxygen-rich efficient counter electrodes for dye-sensitized solar cells. The catalytic activity in graphene may be due to the oxygen containing functional groups (e.g., carboxyls, hydroxyls, epoxides, and carbonyls), achieved by controlling the amount of oxygen functional groups via thermal annealing or acid oxidation. The surface functional groups or heteroatoms can help the adsorption of ions and then improve the hydrophilicity/lipophilicity of the carbon materials, leading to enhanced wettability and facilitated rapid electrolyte ion transport within the micropores. At the same time, the presence of functional groups (e.g., oxygenated groups) on the surface of carbonaceous materials may induce faradaic redox reactions, leading to a 5–10% increase in the total capacitance. Thus, introducing surface functional groups or heteroatoms on the surface of carbon materials appears to be an effective way of improving an electrode’s capacitance. In the present study, we control the degree of carboxylation in the surface of graphene nanoplatelets by thermal and acidic oxidation processes and studied it effects on the performance of electrochemical supercapacitor.

Effect of structural differences of carbon nanotubes and graphene based iridium-NHC materials on the hydrogen transfer catalytic activity

A proper design of heterogeneous molecular catalysts supported on carbon materials requires a systematic study of “metal–carbon support interactions” and their influence on catalytic activity. In this study, hybrid materials containing covalently anchored iridium N-heterocyclic carbene (NHC) organometallic complexes have been successfully prepared from oxidized and partially reduced carbon nanotubes (CNTs). The preparation method for these supported materials relies on the selective functionalization of the superficial hydroxylic groups using the imidazolium salt, 1-(3-hydroxypropyl)-3-methyl-1H-imidazol-3-ium chloride. The hydrogen transfer catalysis activity of these nanotube-based hybrid catalysts was tested by the reduction of cyclohexanone to cyclohexanol with 2-propanol, and the results of the tests were compared with those obtained using similar hybrid graphene-based catalysts. While EXAFS analysis revealed a common first coordination shell of the iridium atom for all the hybrid materials examined, independently of whether they were either supported on carbon nanotubes or graphene materials, catalytic activity in all the reduced materials was significantly superior. Moreover, catalytic systems based on reduced CNTs exhibited a better performance than those based on reduced graphene materials. Both these facts suggest there is a positive correlation between hydrogen transfer catalytic activity, reconstruction of the aromatic carbon structure and the smaller amount of oxygen functional groups.

Oxygen-containing Functional Groups Enhancing Electrochemical Performance of Porous Reduced Graphene Oxide Cathode in Lithium Ion Batteries

Exploring high performance and environment-friendly electrode materials is highly desirable for the sustainable Li-ion batteries (LIBs) system. In this study, a facile approach of the modified Hummers’ method combining with special thermal reduction was proposed to synthesize nanostructured reduced graphene oxide (RGO) with abundant oxygen-containing functional groups. The resultant RGO showed high specific capacity and excellent cyclability as cathode materials for LIBs. The specific capacity of about 220mAhg−1 at a current density of 50mAg−1 was achieved after 100 cycles. More importantly, it was demonstrated that the capacity increased with the increase of the amount of oxygen functional groups, highlighting the significant effects of oxygen-containing functional groups of RGO on high lithium storage performance.

High Yield Preparation of Graphene Oxide Film Using Improved Hummer’s Technique for Current-Voltage Characteristic

Nowadays, graphene (Gr) is one of the most promising materials in the field of nanoscience and nanotechnology and has attracted extensive attention in variety of applications, such as solar energy, environmental management, sensor, electronic device as well as energy storage and conversion. From a theoretical point of view, Gr provides the ultimate two-dimensional (2D) model of a catalytic support with sp2 hybridized carbon atoms. Its unique physical, chemical and mechanical properties are outstanding, and could allow the preparation of this composite material with unprecedented characteristics, such as superior electron mobility, good conductivity, excellent transparent property and high chemical stability. These unique characteristics inherent to well-defined 2D Gr are suitable for facilitating a wide range of transformations and may offer extraordinary potential in the design of novel catalytic systems. Herein, a simple and well-controllable Improved Hummer’s method was presented for the first time by controlling it’s stirring duration for high yield production of GO (62.50%). Based on our preliminary results, it was found that large amount of oxygen functional groups appeared after the conversions of graphite into graphene oxide (GO) by applying the vigorous stirring speed for 72 hours continuously. The main reason mainly attributed to the improvement of the mass transfer rate of oxygen molecules during the oxidation reactions; thus, high yield of GO could be achieved under this experimental condition. In addition, the resultants GO exhibited higher short-circuit currents with 290 μA compare to short circuit of Gr with 70 μA under light simulation condition.

Using Graphene As a Conducting Layer and Barrier Layer for High Aspect Ratio through Silicon Via Filling

Traditional process for TSV fabrication is a dry process that includes the following step: (1) formation of vias by reactive ion etching; (2) formation of a SiO2 isolation liner; (3) deposition of a TiN barrier layer and a copper seed layer; (4) via fill with copper electrodepositing. Herein, we attempt to use graphene to substitute the TiN barrier layer and the copper seed layer for reducing the traditional process procedure. Graphene materials, including single layer and multi-layer graphene platelet, have recently drawn extensive attention due to their outstanding electrical and thermal properties. Reduction of graphene oxide (GO) is a method to prepare the graphene film. Since GO has a large amount of oxygen functional groups, it can be well dispersed in several solvents and enable it to be coated on a substrate by a chemical grafting method using a wet process. In TSV technology, the thermo-mechanical fatigue may lead to failure in the TSV interconnects because the coefficient of thermal expansion (CTE) of copper is much higher than that of silicon. The packaging materials with different CTEs will induce large stresses at interfaces. To overcome this problem, we choose graphene sheets to substitute the copper seed layer since the CTE of graphene is closer to silicon than copper. In our research, we reduce the procedure of TSV fabrication using a wet process to simultaneously substitute barrier and seed layer with graphene, and to replace filled copper with filled nickel-tungsten alloy in high aspect ratio TSV. This replacement can result in lower fabrication cost compared with the traditional TSV process.

The effect of surface characteristics of reduced graphene oxide on the performance of a pseudocapacitor

In this research, we have analyzed the electrochemical characteristics of the different rGO/Co3O4 composites prepared by controlling the rGO surface characteristics and its relationship between the growth of Co3O4 nanoparticles and the performance of the pseudocapacitor. Reduced graphene oxide/cobalt oxide (rGO/Co3O4) nanocomposites of different morphologies were prepared through the simple hydrothermal method. First, different kinds of graphite precursors, crumpled and planar with different properties, were used to determine the most suitable substrate to grow Co3O4 nanoparticles. As a result, rGO/Co3O4 composite synthesized from planar graphite shows a higher specific capacitance of 207.2, 170.1, and 141.5 Fg−1 at 1, 2, and 5 Ag−1 than the one prepared from crumpled graphite. In the second part, planar graphite, confirmed to be the most suitable substrate from the previous part, was oxidized under various oxidation conditions to increase the oxygen functional groups attached on the GO surfaces and observed to see how it affects the growth of Co3O4 nanoparticles and its influence on the electrochemical performance of the rGO/Co3O4 pseudocapacitor. As a result, the one with the largest amount of functional groups had the Co3O4 nanoparticles well dispersed and grown on the rGO substrate in small nanoparticle sizes, as small as 5.9 nm, leading to an improved electrochemical performance. Thus, the specific capacitance with the least amount of oxygen functional groups are 207.2, 170.1, and 141.5 Fg−1 and for the largest amount of functional groups are 411.5, 371.4, and 292.7 Fg−1, at 1, 2, and 5 Ag−1 respectively. This approach could become a guideline for the ideal fabrication of rGO/metal oxide composite for further research involving rGO based pseudocapacitors.