Carbon Surface Functionalities Research Articles

ChemInform Abstract: Carbon Surface Functionalities and SEI Formation During Li Intercalation

AbstractReview: SEI: solid electrolyte interphase; 322 refs.

Stability Enhancement of the Interaction Between Pt Nanoparticles and Carbon Supports through Carbon Surface Functionalization

Proton exchange membrane fuel cells (PEMFCs) that use hydrogen and oxygen in air as fuels to produce electricity have attracted extensive interests over the past decades.1 The high efficiency and zero emission make PEMFCs promising candidates for viable propulsive systems in electric automobiles.2 One of the major challenges that hinder the commercialization of PEMFCs vehicles is the poor stability of Pt nanoparticles on carbon supports, which mainly due to the dissolution and re-deposition of Pt and migration of Pt over carbon supports.3 4Both of them will cause the agglomeration of Pt nanoparticles, resulting in loss of Pt electrochemical surface area (ECSA) and the increasing of activation overpotentials. Aiming to minimize the growth of Pt nanoparticles due to the Pt migration on carbon supports, fundamental understanding of their interaction is required, so as to modify the carbon supports to enhance the binding energy between Pt and carbons. In our recent work, Pt of 3% to 5% loading was deposited on XC-72 carbon black, graphene, functionalized XC-72 carbon black and functionalized graphene, where the Pt clusters or islands of about 3-6 atoms thickness on different supports can be achieved by a general two step method. The dispersion and morphology of Pt on pristine graphene, SO3H-graphene and NH2-graphene were then characterized by high resolution transmission electron microscopy (HRTEM). It is clearly shown that spherical Pt nanoparticles of very small size were uniformed dispersed on functionalized graphene, whereas on pristine graphene, some rod-like Pt crystals were observed. It indicates that the presence of functional groups prevents the migration of Pt nuclei on the two-dimentional graphene sheet during the synthetic process. X-ray absorption near edge structure (XANES) of Pt L-edge and C K-edge were performed to further characterize the interaction between Pt and different supports. The increasing of the intensity of the Pt L-edge adsorption peak compared with unsupported Pt suggests electron withdrawn from Pt to carbon supports might exists between Pt and carbon supports and the interaction strength follows the order of Pt/SO3H-Graphene > Pt/SO3H-XC72 carbon black > Pt/Graphene > Pt/XC72 carbon black. On the other hand, the shift of Pt L-edge adsorption peak to higher photon energy also indicates the possible increase of oxidation state of Pt due to the Pt-C interaction. This study will shed light on the strategy to improve not only the durability but also activity of Pt based catalysts in fuel cells. (1) Gasteiger, H. A.; Markovic, N. M. Science 2009, 324, 48. (2) Debe, M. K. Nature 2012, 486, 43. (3) Xie, J.; Wood, D. L.; More, K. L.; Atanassov, P.; Borup, R. L. Journal of The Electrochemical Society 2005, 152, A1011. (4) Shao-Horn, Y.; Sheng, W. C.; Chen, S.; Ferreira, P. J.; Holby, E. F.; Morgan, D. Topics in Catalysis 2007, 46, 285.

Ionic Liquid Based Approaches to Carbon Materials Synthesis

AbstractIonic liquids (ILs) have attracted continuous interest because of their remarkable physicochemical properties, including high thermal and chemical stability, nonflammability, negligible vapor pressure, designable cation/anion pairs, electrical and ionic conductivity, low melting points, and affinity towards many compounds. These properties make ionic liquids valuable in the creation of new materials and new processes throughout almost the entire field of materials chemistry. An emerging field is the use of ionic liquids in carbon‐based nanomaterials. Initially, ionic liquids were used as self‐templating carbon sources for the generation of unusual carbon materials in which homogeneous heteroatom doping (e.g., N, B, S) can be accomplished fairly easily. Later, ionic liquids were recognized as suitable for use in the conversion of biomass into porous carbon materials, acting as both reaction media and porosity‐directing regulator. Such applications open the door towards the synthesis and accurate tuning of carbon nanostructures, for example, pore structure, morphology, heteroatom doping, and surface functionality. In addition, the hybridization of ionic liquids and nanocarbons enables the development of composites by combining the properties of the ionic liquid (e.g., ionic conductivity or catalytic activity) and those of a host (e.g., chemical or mechanical stability). Currently, although the research of this topic is rapidly expanding, the rational design and synthesis of carbon‐based materials, particularly their applications in energy storage and transformation, is still in its infancy. In this review, we focus on several aspects of ionic liquid derived carbons with the aim of shedding light on this new topic: 1) Ionic liquids as an advanced medium for carbon synthesis, 2) ionogels derived from nanocarbon, 3) ionic liquids as fluid precursors for functional carbons, and 4) ionic liquid derived carbons for heterogeneous catalysis.

Molecular functionalization of graphite surfaces: basal plane versus step edge electrochemical activity.

The chemical functionalization of carbon surfaces has myriad applications, from tailored sensors to electrocatalysts. Here, the adsorption and electrochemistry of anthraquinone-2,6-disulfonate (AQDS) is studied on highly oriented pyrolytic graphite (HOPG) as a model sp(2) surface. A major focus is to elucidate whether adsorbed electroactive AQDS can be used as a marker of step edges, which have generally been regarded as the main electroactive sites on graphite electrode surfaces. First, the macroscopic electrochemistry of AQDS is studied on a range of surfaces differing in step edge density by more than 2 orders of magnitude, complemented with ex situ tapping mode atomic force microscopy (AFM) data. These measurements show that step edges have little effect on the extent of adsorbed electroactive AQDS. Second, a new fast scan cyclic voltammetry protocol carried out with scanning electrochemical cell microscopy (SECCM) enables the evolution of AQDS adsorption to be followed locally on a rapid time scale. Subsequent AFM imaging of the areas probed by SECCM allows a direct correlation of the electroactive adsorption coverage and the actual step edge density of the entire working area. The amount of adsorbed electroactive AQDS and the electron transfer kinetics are independent of the step edge coverage. Last, SECCM reactive patterning is carried out with complementary AFM measurements to probe the diffusional electroactivity of AQDS. There is essentially uniform and high activity across the basal surface of HOPG. This work provides new methodology to monitor adsorption processes at surfaces and shows unambiguously that there is no correlation between the step edge density of graphite surfaces and the observed coverage of electroactive AQDS. The electroactivity is dominated by the basal surface, and studies that have used AQDS as a marker of steps need to be revised.

Adsorptive desulfurization of feed diesel using chemically impregnated coconut coir waste

This study reports the usage of chemically impregnated coconut coir waste (CICCW) as a low-cost adsorbent for the desulfurization of feed diesel. The characterization of the developed adsorbent was focused on quantitative analysis (carbon yield %, proximate, ultimate, carbon surface functionalities, BET surface area and porosity distribution, and particle size analysis), qualitative analysis (FTIR), and optical analysis (SEM). Batch experiments with feed diesel having a total sulfur concentration of 2,050 mg L−1 were conducted to optimize the adsorption parameters such as adsorbent dose, temperature, and contact time. The adsorption process shows an optimum dose of 1 g/20 mL, and the equilibrium is attained in 3 h. The adsorption of sulfur onto the adsorbent at optimum temperature 293 K is regulated by external mass transfer (diffusion into mesopores) followed by a steady adsorption phase with intra-particle diffusion in micropores. A Fickian mechanism controls the diffusion of sulfur molecules from the solution onto the surface of the adsorbent. Freundlich adsorption isotherm illustrates the equilibrium adsorption data very well. The negative value of ΔG° (−27.61 kJ mol−1) and ΔS° (−44.56 J K−1 mol−1) indicates the feasibility, spontaneity of the adsorption process and justified the decrease in the randomness of adsorbed sulfur molecules onto the adsorbent surface, respectively. The exhausted CICCW can be effectively regenerated by methanol and reutilized for three adsorption–desorption cycles. The approximate cost of preparation of the adsorbent was USD 10.714 per kg. These results clearly proved the feasibility of the developed low-cost adsorbent (CICCW) as a good candidate for the desulfurization of feed diesel.

Aptamer-functionalized hybrid carbon nanofiber FET-type electrode for a highly sensitive and selective platelet-derived growth factor biosensor.

Precise selectivity and rapid responses to target biomolecules are important in the development of biosensors. In particular, highly sensitive and selective biosensors have been used in clinical treatment to detect factors such as cancer oncoproteins and endocrine disruptors. Herein, highly sensitive liquid electrolyte field-effect transistor (FET) system biosensors were fabricated to detect platelet-derived growth factor (PDGF) using a PDGF-B binding aptamer conjugated with carboxylic polypyrrole-coated metal oxide-decorated carbon nanofibers (CPMCNFs) as the signal transducer. First, CPMCNFs were fabricated using vapor deposition polymerization (VDP) of the carboxylic pryrrole monomer (CPy) on metal oxide-decorated carbon nanofiber (MCNF) surfaces with no treatment for carbon surface functionalization. Furthermore, a 3 nm thick uniformly coated carboxylic polypyrrole (CPPy) layer was formed without aggregation. The CPMCNFs were integrated with the PDGF-B binding aptamer and immobilized on the interdigitated array substrate by covalent anchoring to produce a FET-type biosensor transducer. The PDGF-B binding aptamer conjugated CPMCNF (CPB-Apt) FET sensor was highly sensitive (5 fM) and extremely selective for isoforms of PDGFs. Additionally, the CPB-Apt FET sensor could be reused over a few weeks.

General approach for electrochemical functionalization of glassy carbon surface by in situ generation of diazonium ion under acidic and non-acidic condition with a cascade protocol

Immobilization of catechol derivatives on GC electrode surfaces can be performed by in situ generation and reduction of nitrocatechol. We present the oxidative nitration of catechol in the presence of nitrous acid followed by electrochemically reduction of the generated nitro aromatic group to the corresponding amine group and its conversion to diazonium cation at the electrode surface to yield a surface covalently modified with catechol. In this manner, some derivatives of catechol can be immobilized on the electrode surface. Whole of the process is carried out in Triethylammonium acetate ionic liquid as an inert and neutral medium (pH∼7.0). Surface coverage can be easily controlled by the applied potential, time and concentration of catechol. After modification, the electrochemical features of modified surface have been studied. Also modified GC electrode exhibited remarkable catalytic activity in the oxidation of NADH. The catalytic currents were proportional to the concentration of NADH over the range 0.01-0.80mM. This condition can be used for modification of GC surfaces by various aromatic molecules for different application such as design of sensors and biosensors.

Facile electrochemical hydrogenation and chlorination of glassy carbon to produce highly reactive and uniform surfaces for stable anchoring of thiolated molecules.

Carbon is a highly adaptable family of materials and is one of the most chemically stable materials known, providing a remarkable platform for the development of tunable molecular interfaces. Herein, we report a two-step process for the electrochemical hydrogenation of glassy carbon followed by either chemical or electrochemical chlorination to provide a highly reactive surface for further functionalization. The carbon surface at each stage of the process is characterized by AFM, SEM, Raman, attenuated total reflectance (ATR) FTIR, X-ray photoelectron spectroscopy (XPS), and electroanalytical techniques. Electrochemical chlorination of hydrogen-terminated surfaces is achieved in just 5 min at room temperature with hydrochloric acid, and chemical chlorination is performed with phosphorus pentachloride at 50 °C over a three-hour period. A more controlled and uniform surface is obtained using the electrochemical approach, as chemical chlorination is observed to damage the glassy carbon surface. A ferrocene-labeled alkylthiol is used as a model system to demonstrate the genericity and potential application of the highly reactive chlorinated surface formed, and the methodology is optimized. This process is then applied to thiolated DNA, and the functionality of the immobilized DNA probe is demonstrated. XPS reveals the covalent bond formed to be a C-S bond. The thermal stability of the thiolated molecules anchored on the glassy carbon is evaluated, and is found to be far superior to that on gold surfaces. This is the first report on the electrochemical hydrogenation and electrochemical chlorination of a glassy carbon surface, and this facile process can be applied to the highly stable functionalization of carbon surfaces with a plethora of diverse molecules, finding widespread applications.

Lignocellulosic-derived modified agricultural waste: Development, characterisation and implementation in sequestering pyridine from aqueous solutions

The development and characterisation of modified agricultural waste (MAW) by H3PO4 activation is addressed in this study for sequestering pyridine from aqueous solutions. The adsorbent is characterised by carbon, hydrogen and nitrogen content of 55.53%, 3.28% and 0.98% respectively. The adsorbent also shows acidic (carboxylic, lactonic, phenolic groups) and basic carbon surface functionalities, functional groups viz. hydroxyl, carboxylic acid and bounded water molecules, BET surface area of 1254.67m2g−1, heterogeneous surface morphology and graphite like XRD patterns. Adsorption of pyridine is executed to evaluate the adsorptive uptake in batch (qe=107.18mgg−1) as well as in column system (qe=140.94mgg−1). The adsorption process followed the pseudo-second-order kinetics with the Langmuir isotherm best representing the equilibrium adsorption data. The thermodynamic parameters (ΔHo=9.39kJmol−1, ΔGo=−5.99kJmol−1, ΔSo=50.76JK−1mol−1) confirm the endothermic and spontaneous nature of the adsorption process with increase in randomness at solid/solution interface. The adsorption mechanism is governed by electrostatic and π–π dispersive interactions as well as by a two stage diffusion phenomena. Thermally regenerated spent MAW exhibited better adsorption efficiency for five adsorption–desorption cycles than chemically regenerated. The low-cost of MAW (USD 10.714 per kg) and favourable adsorption parameters justifies its use in the adsorptive removal of pyridine.

Physical Characteristics of New Potential Electrolytes for High Energy and Power Density Electrochemical Devices

Physical Characteristics of New Potential Electrolytes for High Energy and Power Density Electrochemical Devices

Valorization of agricultural waste into activated carbons and its adsorption characteristics for heavy metals

Abstract Activated carbon derived from pine cones waste was prepared by carbonization at 450°C, activated by different activating agents: ZnCl 2, H 2 SO 4 and NaOH, and then pyrolyzed at 600°C. Adsorption of Cr VI and other heavy metals (Mn II, Fe II, Cu II) on activated carbons was investigated to evaluate the adsorption properties. Special attention was paid to the effects of carbon surface functionalities that were analyzed by FT-IR and zeta potential study. Moreover, XRD study of activated carbon was also carried out. Results had shown that activated carbon by NaOH was the best adsorbent for removal of chromium VI from wastewater. The solid-solution interaction was determined by analyzing the adsorption isotherms at room temperature at different pH. When pH is above 4, the removal fraction of Cr (VI) ions decreased with the increase of pH. The removal fraction of Cr (VI) ions decreased below pH 4. The preferable removal of Cu (II) over Mn(II) and Fe (II) could be due to its lower affinity to solvent.Pseudo-second order equation provided the better correlation for the adsorption kinetics data. Equilibrium isotherms were determined by Fowler-Guggenheim model.

Effect of liquid-phase O3 oxidation of activated carbon on the adsorption of thiophene

In this work, a combined experimental and computational study is carried out to investigate the effect of O3 oxidation of activated carbon (AC) in various types of aqueous media (alkaline, acidic and neutral aqueous solutions) on the adsorption of thiophene. A high surface area AC (BET surface area of 2880m2/g) is modified by ozone-oxidation in different aqueous media under ambient conditions. Experimental results show liquid phase ozone oxidation of AC introduces oxygen functional groups to the AC surface, resulting in enhanced adsorption capacity of thiophene. The impact of oxidation media on the adsorption capacity follows the order of NaOH>H2SO4>H2O, consistent with the order of the concentrations of oxygen functionalities introduced on the carbon surface. Computational results suggest that phenol and carboxyl groups on the surface lead to stronger thiophene adsorption than the bare (unfunctionalized) graphite surface, corroborating our experimental results. Additionally, the presence of bridging-oxygen functionalities on the carbon surface leads to extremely exothermic adsorption energies of thiophene, which can be attributed to sulfoxide formation and H-bonding interactions. DFT calculations suggest the adsorption strength of thiophene follows the order of bridging-O-functionalized (Ads E=−1.51eV)≫OH-functionalized (Ads E=−0.36eV)>COOH-functionalized (Ads E=−0.27eV)>bare graphite (Ads E=−0.26eV). The combined experimental and computational study provides direction for carbon surface functionalization for adsorptive desulfurization.

Modification of Carbon Electrodes by Anodic Oxidation of Organic Anions

Functionalization of carbon surfaces was first carried out in electrode pre-treatments under drastic electrolysis conditions. As a result of these treatments, the electrode carbon surfaces were modified without selectivity with a wide variety of oxygenated functional groups. However, this lack of selectivity was partially overshot with some electrochemical strategies of covalent immobilization, such as the reduction of aryldiazonium, arylsulfonium and iodonium salts, the oxidation of amines, alkynes and arylacetates. In a variant of these direct methods, the oxidation of the carbon surfaces in presence of alcohols and alkyltrimethylsilanes has also been developed. This sort of derivatization has opened the possibility to incorporate a wide variety of functional groups according to the desired applications. In the majority of these methods, reactive intermediates such as organic free radicals and carbocations are generated, which react with the sp2 carbon atoms of the surface to produce covalently modified electrodes. In the particular case of the oxidation process of carboxylates, the loss of carbon dioxide is accompanied with the formation of free radicals and by analogy, it is proposed in this work that other organic anions are also susceptible to be oxidized to yield free radicals that could be covalently attached to carbon electrodes.

A Simple Method to Tune Up Screen‐Printed Carbon Electrodes Applicable to the Design of Disposable Electrochemical Sensors

AbstractWe report an easy method to tune up screen‐printed carbon electrodes (SPCEs) for application in fabricating disposable electrochemical sensors. Simply by ultrasonic polishing a bare SPCE in a γ‐Al2O3 slurry, the surface roughness was drastically smoothed coupled with a large increase in hydrophilicity. The as‐generated micromorphology on the surface of the SPCE was found to be ideal for the immobilization of catechol to minimize the overpotential in the sensitive detection of nicotinamide adenine dinucleotide (NADH) and hydrazine. Physical characterization by both XPS and AFM studies specify that the adsorption behavior is related to the carbon surface functionalities and the trapping of γ‐Al2O3 on the polished‐SPCE.

Electrografting via Diazonium Chemistry: From Multilayer to Monolayer Using Radical Scavenger

A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a radical scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the radical capture was confirmed by isolation of the aryl radical/DPPH coupling product.

High-Performance Hybrid Catalyst with Selectively Functionalized Carbon by Temperature-Directed Switchable Polymer

Carbon-supported Pt (Pt/C) catalyst was selectively functionalized with thermally responsive poly(N-isopropylacrylamide) (PNIPAM) to improve water transport in the cathode of proton exchange membrane fuel cell (PEMFC). Amine-terminated PNIPAM selectively reacted with the functional group of −COOH on carbon surfaces of Pt/C via the amide reaction by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a catalyst. Pt surfaces of Pt/C were intact throughout the carbon surface functionalization, and the carbon surface property could be thermally changed. The PNIPAM-functionalized Pt/C was well-dispersed, because of its hydrophilic surface property at room temperature during the catalyst ink preparation. In sharp contrast, when PEMFC was operated at 70 °C, PNIPAM-coated carbon surface of Pt/C became hydrophobic, which resulted in a decrease in water flooding in the cathode electrode. Because of the switched wetting property of the carbon surface, PEMFC with PNIPAM-functionalized Pt/C catalyst in the cathode ...

Oxidation is Key for Black Carbon Surface Functionality and Nutrient Retention in Amazon Anthrosols

Oxidation is Key for Black Carbon Surface Functionality and Nutrient Retention in Amazon Anthrosols

Oxidation is Key for Black Carbon Surface Functionality and Nutrient Retention in Amazon Anthrosols

Aims: Soil black carbon (BC) has been shown to possess large amounts of cation exchange sites and surface charge, and is viewed as a potential soil amendment to improve nutrient retention and for pollutant remediation. This study investigated the nanoscale distribution of reactive functional groups and the binding of cations on the surface of micron-size BC particles, identified the key processes, and explored the sources of surface functionality and their relative contribution to cation exchange capacity (CEC). Materials and Methods : Elemental microprobe and synchrotron-based Scanning Transmission X-ray Spectromicroscopy (STXM) coupled with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were used for nano-scale mapping of

Effect of the nanotube aspect ratio and surface functionalization on the morphology and properties of multiwalled carbon nanotube polyamide‐based fibers

AbstractIn this study, the effect of the carbon nanotube (CNT) aspect ratio and surface functionalization on the mechanical behavior and morphological changes of polyamide (PA)‐based fibers was investigated. Composites were prepared by the melt blending of CNTs with PA, and at a later time, the fibers were prepared by melt spinning and cold drawing. A reinforcement effect was noticed for all of the CNTs samples, and the increase in the mechanical properties and dimensional stability was more pronounced for highly oriented filaments. When the elongational flow was increased, the orientation of CNTs along the fiber direction was observed, but the nanotube alignment was much more difficult for CNTs with ultrathin outer diameters because of nanotube waviness and folding. Moreover, the presence of functional groups on the CNT surface hindered their orientation along the fiber direction because some interaction between the functional groups could occur. The morphological variations of the oriented, anisotropic fibers, as studied with transmission electron microscopy, scanning electron microscopy, small‐angle X‐ray scattering, and differential scanning calorimetry analysis, were correlated with changes in the mechanical behavior. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Diels–Alder reactions for carbon material synthesis and surface functionalization

To meet the ever growing demand for carbon nanomaterials with tailored properties, Diels–Alder reactions are emerging as an efficient alternative to other synthetic methods. From an application perspective, the development of convenient surface functionalization strategies for carbon nanostructures is of paramount importance. Pristine carbon nanostructures display a natural tendency to undergo Diels–Alder reactions with a range of functional dienes and dienophiles without the need of a catalyst. This has sparked significant scientific interest in exploiting the Diels–Alder reaction as a powerful strategy for their synthesis as well as for their subsequent surface functionalization. The present review highlights the remarkable role of Diels–Alder reactions for the synthesis of fullerenes, carbon nanotubes and graphene, and its promise as a facile carbon nanostructure functionalization strategy with small molecules and polymer chains. A critical overview of the recent developments evidencing the potential of Diels–Alder reactions as an efficient route to carbon based functional materials is presented.