Surface Modification Of Carbon Research Articles

Impact of Carbon Support Functionalization on the Electrochemical Stability of Pt Fuel Cell Catalysts

Nitrogen-enriched porous carbons have been discussed as supports for Pt nanoparticle catalysts deployed at cathode layers of polymer electrolyte membrane fuel cells (PEMFC). Here, we present an analysis of the chemical process of carbon surface modification using ammonolysis of preoxidized carbon blacks, and correlate their chemical structure with their catalytic activity and stability using in situ analytical techniques. Upon ammonolysis, the support materials were characterized with respect to their elemental composition, the physical surface area, and the surface zeta potential. The nature of the introduced N-functionalities was assessed by X-ray photoelectron spectroscopy. At lower ammonolysis temperatures, pyrrolic-N were invariably the most abundant surface species while at elevated treatment temperatures pyridinic-N prevailed. The corrosion stability under electrochemical conditions was assessed by in situ high-temperature differential electrochemical mass spectroscopy in a single gas diffusion lay...

Effect of Anionic Surfactant on Adsorption Properties of Nano Calcium Carbonate

Because of its superior surface properties, nanocalcium carbonate can be applied to the adsorption of heavy metals in wastewater. However, because of the easy aggregation of nanocalcium carbonate, high surface energy and poor dispersibility in water, it is not conducive to the process of adsorption. Therefore, surface modification of nanocalcium carbonate is needed. In this paper, nanocalcium carbonate was prepared by liquid phase method. And the nanocalcium carbonate was surface modified by sodium dodecyl sulfate. The effects of modifier amount, modification temperature, and modification time on the activation and absorbance of nanocalcium carbonate were investigated. And the morphology and particle size of modified nanocalcium carbonate were tested by SEM and XRD patterns.The results show that the dispersion and surface activity of the modified nanocalcium carbonate have been improved remarkably. Moreover, the Cu2+ was adsorbed by sodium dodecyl sulfate modified nanocalcium carbonate and unmodified nanocalcium carbonate under the optimum modification conditions. And the effects of nanocalcium carbonate initial concentration on the adsorption performance were studied. The results show that the adsorption performance of modified calcium carbonate is better than that of the unmodified. Moreover, the adsorption process is studied by adsorption isotherm. By drawing the adsorption isotherms lines and by comparing the fitting result of the experimental data based on the Langmuir model and that of Freundlich model, it is found that the adsorption of Cu2+ by modified nanocalcium carbonate meets the Langmuir model.

The Role of the Supporting Electrolyte on the Covalent Modification of Carbon Surfaces with Organic Groups

Covalent modification of carbon electrodes has been developed during the last 30 years with the implementation of different reduction or oxidation electrochemical strategies [1]. These methods have been of interest for many applications due to the physical and chemical stability of the grafted films. Among these methods, the direct and mediated oxidation of carboxylates allowed the attachment of organic groups like saturated [2] and unsaturated alkyl chains [3] and substituted benzylic [4] and phenylalkylic groups. When the grafted film bears moieties electrochemically actives, they can be characterised through their response in cyclic voltammetry experiments, however, the main features of the redox active groups are far from the ideal behaviour for adsorbed species [4]. Therefore, in this work is analysed the effect of the cation size of the supporting electrolyte used during the grafting by mediated oxidation of 4-nitrophenylbutyrate on the ideality of the redox process of the nitrobenzene group. It was found that the reversible reduction process of the adsorbed nitrophenyl groups is closer to an ideal behaviour when the size of the supporting electrolyte cation follows the next order: n-Hx4N+ > n-Bu4N+ > Et4N+ > Me4N+. This order reveals different levels of compactness of the grafted film and explain the behaviour of ferrocene as redox probe, whose apparent reversibility decreases in the same order of cation size.

Surface modification of sludge-derived carbon by phosphoric acid as new electrocatalyst for degradation of acetophenone.

Sludge-derived carbons (SCs) were modified by different acids and used as electrocatalyst for electrochemical oxidation degradation of acetophenone. The results showed that SC treated with phosphoric acid (H3PO4-SC) exhibited the highest catalytic activity. The degradation efficiency of acetophenone reached 87.0%, and TOC removal was 72.3% under the conditions of 100mgL-1 acetophenone, 90mAcm-2, and 180min reaction time. The element content and chemical state of H3PO4-SC were measured by XRF, XRD, TGA, FTIR, and Mössbauer spectra, and the results indicated that ferric iron and phosphate on the surface of H3PO4-SC might play the main role in acetophenone degradation. The carbonyl-13C-labeled acetophenone was first used to investigate the degradation of acetophenone in electrochemical oxidation by NMR.

Preparation and surface modification of PVDF-carbon felt composite bipolar plates for vanadium flow battery

Abstract The performance of vanadium flow batteries (VFBs) is closely related to the materials used in the bipolar plates. Carbon-based composite bipolar plates are particularly suitable for VFB applications. However, most original preparation methods cannot simultaneously achieve good electrical conductivity and mechanical performance. In this paper, we propose a novel approach to fabricating bipolar plates with carbon plastic materials, including four steps, namely coating a poly (vinylidene fluoride) (PVDF) solution onto carbon felt, solvent evaporation, hot-pressing, and surface modification. The resulting bipolar plates showed high conductivity, good mechanical strength, and corrosion resistance. Surface modification by coating with carbon nanotubes (CNTs) removed the PVDF-rich layer from the surface of the carbon fibers. The high surface area of the CNT withdrew PVDF resin from the carbon fiber surface, and promoted the formation of a conductive network. The flexibility and battery charge-discharge cycle measurements showed that the composite bipolar plates can meet requirements for VFB applications.

Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1V with a low limit of quantification 5.94nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare.

Determination of specific capacitance of modified candlenut shell based carbon as electrode material for supercapacitor

Surface modification of candlenut shell carbon (CSC) using three chemicals: nitric acid (HNO3), hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) has been carried out. Activation of CSC was performed using H3PO4 solution with different ratio between CSC and activator. Carbon surface area was determined by methylene blue adsorption method. Surface characterization was performed using FTIR spectroscopy and Boehm titration method. Specific capacitance of electrode prepared from CSAC (candlenuts shell activated carbon) materials was quantified by Cyclic Voltammetry (CV) measurement. The surface area before and after activation are 105,127 m2/g, 112,488 m2/g, 124,190 m2/g, and 135,167 m2/g, respectively. Surface modification of CSAC showed the improvement in the chemical functionality of CSAC surface. Analyses using FTIR spectroscopy and Boehm titration showed that modifications with HNO3, H2SO4 and H2O2 on the surface of the CSAC increased the number of oxygen functional groups. As a consequence, the specific capacitance of CSAC modified with 65% HNO3 attained the highest value (127 μF/g). There is an incredible increase by a factor of 298% from electrode which was constructed with un-modified CSAC material. This increase correlates to the largest number of oxygen functional groups of CSAC modified with nitric acid (HNO3).

Anti-corrosion and wear resistance properties of polymer composite coatings: Effect of oily functional fillers

Abstract We herein report the development of carbon-modified porous fillers that function as micro-reservoirs to store lubricating oil as a low-friction and anticorrosive agent in a composite coating. These novel oily particles were added to an epoxy resin (EP)-based coating to study the effect of a lubricating oil on the anti-corrosion and friction performances of the coating. Analysis by electrochemical impedance spectroscopy and sliding wear tests demonstrated that the presence of particles containing the lubricating oil significantly improved the barrier properties and the wear resistance of the EP coating. It was therefore apparent that the carbon surface modification of the Celatom filler improved the compatibility of both the filler towards the resin. Thus, the addition of fillers containing lubricating oil further improved the wear resistance and anti-corrosion properties of the coatings.

Nanoscale mapping of catalytic hotspots on Fe, N-modified HOPG by scanning electrochemical microscopy-atomic force microscopy.

The scanning electrochemical microscopy-atomic force microscopy (SECM-AFM) technique is used to map catalytic currents post Fe and N surface modification of graphitic carbon with an ultra-high resolution of 50 nm. The oxidation current of the partial reduction product, hydrogen peroxide, was also mapped in the same location in the graphitic carbon. The current mapping and ex situ spectroscopic evidence revealed that Fe-coordinated nitrogen sites formed both in the edge and basal planes of highly ordered pyrolytic graphite (HOPG) constitute the primary oxygen reduction catalytic sites in acid solutions of this important yet insufficiently understood class of catalysts.

Surface modification of biomass-derived hard carbon by grafting porous carbon nanosheets for high-performance supercapacitors

PCNS/BHC composites were prepared by grafting PCNSs with high graphitization degree and abundant pores onto BHC surfaces for high-performance supercapacitors.

Thermal treatment to improve the hydrophobicity of ground CaCO3 particles modified with sodium stearate

The surface modification of calcium carbonate (CaCO3) particles, which is used as a filler, significantly affects the properties of the composed materials. The effects of thermal treatment on ground calcium carbonate (GCC) particles subjected to hydrophobic modification using sodium stearate (RCOONa) were studied. The contact angle of the modified GCC particles increased from 24.7° to 118.9° when the amount of RCOONa added was increased from 0% to 5% and then decreased to 97.5° when the RCOONa content was further increased to 10%. When a large amount of RCOONa was added, RCOO− reacts with Ca2+ and generates (RCOO)2Ca nuclei, which are adsorbed on the surface of the GCC particles, forming a discontinuous (RCOO)2Ca modified layer. After thermal treatment under sealed conditions, the contact angle of the GCC particles modified using 1.5% RCOONa/GCC increased from 112.8° to 139.6°. The thermal stability of the (RCOO)2Ca modified layer was increased, with the temperature increase of the mass-loss peak from 358.0 to 463.0 °C. It is confirmed that the spreading of melted (RCOO)2Ca nuclei on the surface of the GCC particles during the thermal treatment increased the continuity of the modified layer, converting the physical adsorption of the (RCOO)2Ca nuclei into chemisorption. The grafting density of RCOO− on the GCC particle surface after thermal treatment approximates to 5.00/nm2, which is close to the single-molecular-layer grafting density of RCOO−, indicating that excellent modification was achieved.

The effects of surface modification of ground calcium carbonate powdery fillers on the properties of PVC

The effects of surface modification of ground calcium carbonate (GCC) particles on the thermal and mechanical properties of poly(vinyl chloride) (PVC) based composites were investigated. Aminopropyltrimethoxysilane (APS) was used as a modifier for GCC particles. The experimental results indicated that the pre-treatment of GCC particles with NaOH promoted the formation of OH− on the surface of GCC particles, which improved the graft of APS on GCC surface and enhanced the interfacial interaction between GCC particles and PVC matrix. The SEM micrographs of the PVC filled with different GCC particles showed that the dispersion of fillers in the PVC matrix was improved by surface modification. The results of TG showed that the thermal properties of PVC filled with NaOH/APS modified GCC particles (PVC/GCC–OH–APS) outweighed those of PVC filled with APS modified GCC particles (PVC/GCC–APS) or raw GCC particles (PVC/GCC). Compared with the use of raw GCC, the use of the surface modified GCC particles, especially the GCC–OH–APS, led to the increase of the tensile strength and impact strength of the composites.

Surface modification of basic copper carbonate by mechanochemical processing with sulfur and ammonium sulfate

Mechanochemical phenomena including mechanical activation and direct reaction have been widely observed particularly from dry grinding operation and various applications of the phenomena have been reported in many fields of chemistry. A new approach was introduced here to trigger partial reaction by co-grinding samples with small addition of water/liquid to achieve the purpose of surface modification with new phase formed. As one example, basic copper carbonate was wet ground with elemental sulfur and appropriate additives such as ammonium sulfate to transform the surface chemical composition from oxide to sulfide. Physicochemical characterizations of the prepared samples were conducted by a set of analytical methods, including X-ray diffraction analysis, Fourier Transform infrared spectroscopy, Raman spectroscopic analysis, SEM morphology analysis, Zeta potential and the dissolved copper concentration measurement. The beneficiation efficiency of the modified copper carbonate by a conventional froth flotation used usually for sulfide minerals was examined as a quantitative evaluation to optimize the experimental conditions for the modification operation. A metal yield over 80% was obtained easily after one step concentrating of the flotation operation, indicating that mechanochemically surface controlling concept may serve as a novel pathway to enrich and recycle carbonate-style nonferrous resources by applying the traditional mineral processing technology on the modified samples.

Carbon Surface Modifications by Plasma for Catalyst Support and Electrode Materials Applications

Plasma has been introduced in recent years as a promising method for modification of carbon materials in comparing with traditional wet chemical method, thanks to reduced energy combustion, shortened synthesis duration and undestroyed bulk structure. In this review, we present the modification of carbons on surface chemistry and the recent progress in the applications of these modified carbons in catalyst supports and electrode materials. Plasma methods show promise as a means of enhancing surface properties without destroying the bulk structure of the carbon. Interaction can occur with oxygen, nitrogen and halogens and the chemical modification at the surface can often lead to the provision of sites that can be used to anchor small (nano) particles of metals and active components. This in turn can lead to enhanced catalytic behavior, including electrocatalysis. Hydrophilic/hydrophobic properties can also be tuned via this approach, Carbons modified in this way have also shown promise as high performance electrode materials and pseudocapacitors. The review also mentions challenges and opportunities for further modification of carbons by plasma treatment and for broadening their applications.

Poly arginine-graphene quantum dots as a biocompatible and non-toxic nanocomposite: Layer-by-layer electrochemical preparation, characterization and non-invasive malondialdehyde sensory application in exhaled breath condensate

This study reports on the electropolymerization of a low toxic and biocompatible polymer with entitle poly arginine-graphene quantum dots (PARG-GQDs) as a novel strategy for surface modification of glassy carbon (GC) surface and preparation a new interface for biomedical application. The fabrication of PARG-GQDs on GCE was performed using Layer-by-layer regime. Scanning electron microscopy (SEM) was confirmed dispersion of GQDs on the surface of PARG which lead to increase of surface coverage of PARG. The redox behavior of prepared sensor was then characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CHA), square wave voltammetry (SWV), linear sweep voltammetry (LSV). The electroactivity of PARG-GQDs coating towards detection and determination of malondialdehyde (MDA) as one of the most common biomarkers of oxidative stress, was then studied. Then, application of prepared sensor for the detection of MDA in exhaled breath condensate (EBC) is described. Electrochemical based sensor shows the lower limit of quantification (LLOQ) were 0.329nanomolar. This work is the first report on the integration of GQDs to poly amino acids. Further development can lead to monitoring of MDA or other exhaled breath biomarkers by GQDs functionalized poly amino acids in EBC using electrochemical methods.

Carbon dioxide capture using ammonium sulfate surface modified activated biomass carbon

Activated carbon (AC) was produced by phosphoric acid activation and microwave pyrolysis of Douglas fir biomass. A low temperature activated carbon surface modification method was tested using ammonium sulfate. This method successfully enhanced the carbon dioxide adsorption capacity of Douglas fir biomass based activated carbons. The activated carbon produced, was comparable to commercial grade modified carbon in terms of breakthrough time and adsorption capacity. All modified carbons were selective to carbon dioxide over methane. Activated carbon produced by a phosphoric acid impregnation ratio of 3:1, and modified with an ammonium sulfate mass fraction of 9.1%, had the highest breakthrough time and exhaustion time of 3.5 min and 13.5 min respectively. This carbon adsorbed 97% carbon dioxide from the inlet stream containing methane and other gases with a carbon dioxide over methane selectivity of 5.27. A 1 h exposure of the used carbon to a 105 °C regeneration removed a majority of the carbon dioxide and methane on the carbon surface, facilitating regeneration.

Synthesis and discharge performances of NiCl2 by surface modification of carbon coating as cathode material of thermal battery

The high solubility in molten salt and low conductivity of NiCl2, compared with traditional FeS2 and CoS2, have become the restrictions for its extensive application in cathode materials of thermal batteries. In this study, carbon coated NiCl2 cathode is successfully fabricated by the carbonization of stearic acid. The high specific energy of 641Whkg−1 at current densities of 0.5Acm−2 are observed for the carbon coated NiCl2 thermal batteries, which is higher than the pure NiCl2 with 475Whkg−1. The high specific energies and high-current discharge ability are attribute to the graphite and amorphous carbon layers on the surface of NiCl2 crystalline, which were detected by TEM after carbonization. The graphite layers can improve the conductivity of NiCl2. Meanwhile the coated carbon structure could reduce the solubility of NiCl2 in molten salt.

Thermal Analysis on Monopolar Electrosurgery Device with Novel Electrode for Minimizing Tissue Damage Using Computer-Aided System

The aim of the present study was to investigate the thermal injury in the liver after a minimally invasive electrosurgery with a titanium dioxide (TiO2), a chromium nitride (CrN) and a diamondlike carbon (DLC) surface modifications. Three-dimensional (3-D) liver models were reconstructed using magnetic resonance imaging to simulate the electrosurgical procedure. Several reports have investigated 3D finite element models for electrosurgical devices, but few have examined a model for devices with treated layers. Data indicated that the temperature decreased significantly when minimally electrosurgery with nanostructured TiO2, CrN and DLC thin films were used. Moreover, DLC electrosurgery created a relatively small thermal injury area and decreased 12.93% temperature compared with control groups. The present study reveals that the novel nanostructured thin film on electrode substrates is an effective means of improving the performance of reducing excessive thermal injury and uniformly distributing temperature in the liver.

Surface Modification of AISI 440B Stainless Steel and its Influence on Surgical Drill Bits Performance

Abstract The development of modern invasive surgery is highly dependent on the performance of surgical instruments, understood as long-term efficiency arising from high resistance to wear and corrosion. In order to maintain sufficient reliability, surgical cutting instruments are often made of martensitic stainless steels. Nevertheless, the use of ferrous alloys in medical applications is still a concern due to their questionable corrosion and wear resistance. To extend their biocompatibility, improve stability in variable environmental conditions, improve ease of handling, and maximize their performance, diffusion layers and coatings are applied to the surface. The aim of this work was to evaluate the effect of TiN and diamond-like carbon (DLC) surface modification on the performance of surgical drill bits, that is, wear and corrosion resistance, measured in model and field tests. Based on the findings presented, DLC layers can be recommended as anti-wear and anti-corrosion coatings for surgical drill bits.

Bioactive carbon–PEEK composites prepared by chemical surface treatment

Polyetheretherketone (PEEK) has attracted much attention as an artificial intervertebral spacer for spinal reconstruction. Furthermore, PEEK plastic reinforced with carbon fiber has twice the bending strength of pure PEEK. However, the PEEK-based materials do not show ability for direct bone bonding, i.e., bioactivity. Although several trials have been conducted for enabling PEEK with bioactivity, few studies have reported on bioactive surface modification of carbon–PEEK composites. In the present study, we attempted the preparation of bioactive carbon-PEEK composites by chemical treatments with H2SO4 and CaCl2. Bioactivity was evaluated by in vitro apatite formation in simulated body fluid (SBF). The apatite formation on the carbon–PEEK composite was compared with that of pure PEEK. Both pure PEEK and carbon-PEEK composite formed the apatite in SBF when they were treated with H2SO4 and CaCl2; the latter showed higher apatite-forming ability than the former. It is conjectured that many functional groups able to induce the apatite nucleation, such as sulfo and carboxyl groups, are incorporated into the dispersed carbon phase in the carbon–PEEK composites.