Electrochemical Oxidation Method Research Articles

Pollutant Removal from Synthetic Aqueous Solutions with a Combined Electrochemical Oxidation and Adsorption Method.

Eliminating organic and inorganic pollutants from water is a worldwide concern. In this study, we applied electrochemical oxidation (EO) and adsorption techniques to eliminate ammonia, phenols, and Mo(VI) from aqueous solutions. We analyzed the first stage (EO) with response surface methodology, where the reaction time (1–3 h), initial contaminant concentration (10–50 mg/L), and pH (3–6) were the three independent factors. Sodium sulfate (as an electrolyte) and Ti/RuO2–IrO2 (as an electrode) were used in the EO system. Based on preliminary experiments, the current and voltage were set to 50 mA and 7 V, respectively. The optimum EO conditions included a reaction time, initial contaminant concentration, and pH of 2.4 h, 27.4 mg/L, and 4.9, respectively. The ammonia, phenols, and Mo elimination efficiencies were 79.4%, 48.0%, and 55.9%, respectively. After treating water under the optimum EO conditions, the solution was transferred to a granular composite adsorbent column containing bentonite, limestone, zeolite, cockleshell, activated carbon, and Portland cement (i.e., BAZLSC), which improved the elimination efficiencies of ammonia, phenols, and molybdenum(VI) to 99.9%. The energy consumption value (8.0 kWh kg−1 N) was detected at the optimum operating conditions.

Electrochemical Valorization of Furfural to Maleic Acid

Maleic acid (MA) is a platform chemical used for various industrial processes. In this study, a new electrochemical oxidation method that can convert furfural, which is one of the most important C5 platform chemicals derived from cellulosic biomass, to MA is reported. This method can produce MA in aqueous media under ambient temperature and pressure without the use of oxidizing agents. The use of acidic media, which promotes opening of the furan ring during oxidation, was critical for the formation of MA. PbO2, MnO2, and Pt, which are stable in acidic solutions under strongly oxidizing potentials, were investigated as anodes for furfural oxidation. The results showed that PbO2 is the only catalyst that can convert furfural to MA as the major product. It was also revealed that the electrochemical conversion of furfural to MA proceeds with 2-furanol as an intermediate.

Carbide-Derived Carbon As Electrode Materials of Electrochemical Double Layer Supercapacitors in Ionic Liquid Electrolytes

Carbide-derived carbon (CDC) is a type of porous pure carbon material that is prepared by chlorination or oxidation of metal carbide precursors, which remove the metal elements from the carbides leaving the porous structure. CDC has been shown to be an advanced electrode material for electrochemical double layer supercapacitors (EDLS) bearing large specific energy and power densities, excellent compatibility with various electrolytes solutions, and a long shelf-life. In this work, we investigate the properties of the electrode materials when room temperature ionic liquids (ILs) are used as the electrolytes for the EDLS. ILs have excellent thermal stability and negligible vapor pressures which can improve the safety and longevity of the electrochemical devices. The CDC electrode materials are synthesized by the chlorination method and a newly developed electrochemical oxidation method. Pure ILs with various cations and anions, IL solutions with different solutes such as organic acids, Li+, Cl-, and propylene carbonate are used in the EDLS systems. In addition to the electrochemical measurements, the morphology and structure properties of the CDC electrode are characterized by Raman spectroscopy, SEM, and XRD techniques.

Electrochemical Oxidation/Modification of Lignin Mediated By Aminoxyl Radicals

Lignin is an abundant biopolymer with an aromatic backbone and offers a bio-based source of aromatic commodity chemicals upon depolymerization.[i] Oxidation methods are widely used for the deconstruction of lignin; successful examples include oxidative delignification in the pulp and paper industry and breakdown of lignin by oxidative fungal enzymes. The hydroxyl functional groups of lignin are particularly susceptible to oxidation. Building on these concepts, our group recently began exploring the controlled oxidation of lignin hydroxyl groups as a means to facilitate lignin depolymerization.[ii] We previously reported an aerobic oxidation method that employs aminoxyl radicals, such as TEMPO, as the catalyst. Acid treatment of the resulting oxidized lignin lead to depolymerization, affording up to 60 wt% yield of low-molecular-weight aromatic compounds.[iii]Aminoxyl radicals undergo facile electron transfer at the electrode surface to generate an oxoammonium species that is reactive towards hydroxyl oxidation (Figure 1a). This facile electron transfer provides a foundation for selective oxidation of hydroxyl groups under electrochemical conditions.[iv] This talk will highlight some of our advances in the use of aminoxyl radicals as mediators for chemoselective oxidation of hydroxyl groups in the structure of lignin. The beta-O-4 linkage (Figure 1b) is the most prevalent linkage in the structure of lignin that includes hydroxyl functional groups and was used as the model for this study. Nitroxyl-mediated electrochemical oxidation methods enable selective and quantitative conversion of the primary hydroxyl group of lignin and beta-O-4 model compounds to the corresponding carboxylate under mildly basic conditions. The modified lignin has a high loading of carboxylic acids, which enhance its water solubility relative to native lignin. The sodium salt of the modified lignin behaves as a polyacid polyelectrolyte in aqueous solution. Acid treatment of the oxidized lignin model affords approximately 30 wt% of monomeric aromatic compounds. [i]. Upton, B. M.; Kasko, A. M. Chem. Rev., 2016, 116, 2275. [ii]. Rahimi, A.; Azarpira, A.; Kim, H.; Ralph, J.; Stahl, S. S. J. Am. Chem. Soc. 2013, 135, 6415. [iii]. Rahimi, A.; Ulbrich, A.; Coon, J. J.; Stahl S. S. Nature 2014, 515, 249. [iv]. Rafiee, M; Miles, K. C.; Stahl, S. S. J. Am. Chem. Soc. 2015, 137, 14751. Figure 1

Fabrication of underwater superoleophobic metallic fiber felts for oil-water separation

Hierarchical nanoneedles-like Cu(OH)2 structure coated stainless steel fiber felts (SSFF) with underwater superoleophobic (154° ± 2.2°, n-octane, oil contact angle) and low-adhesive properties have been successfully fabricated via simple nanoparticles deposition and electrochemical oxidation methods. Meanwhile, when a water droplet (5 μL) contacted the SSFF/Au/Cu/Cu(OH)2 surface, it spread out quickly and reached a 0° CA with very short time, suggesting a superior superhydrophilic property. The SSFF/Au/Cu/Cu(OH)2 was used to separate oil-water mixtures, oil-corrosive salt solution mixtures and oil-in-water emulsions with high efficiency, which allowed water to permeate through while retained oil. In addition, the SSFF/Au/Cu/Cu(OH)2 still maintained high separation efficiency above 99% after 5 emulsion recycling separation times.

Investigation on voltaic effect based on one-dimensional TiO2 nanotube array thin film

This work is to develop a high-reliability long-life high-conversion-efficiency radio-isotope microbattery in order to meet power requirements of micro-electromechanical systems, micro-sensors, micro-actuators, wireless sensing net, and other electron devices working in harsh circumstances, such as polar, desert, subsea, outer surface, etc. Compared with traditional dry batteries, chemical batteries, fuel cells and solar cells, the radioactive isotope batteries have long service life, higher energy density, strong adaptability to environment, good work stability, no maintenance, and miniaturized size, etc. These advantages make the voltaic battery an attractive alternative. In this paper we present a voltaic battery with enhanced voltaic effect by using a wide-bandgap semiconductor TiO2 nanotube array thin film. An electrochemical anodic oxidation method is used to prepare the vertically oriented and highly ordered TiO2 nanotube array film on Ti plate. Electrolyte solution consists of ammonium fluoride, ethylene glycol, and deionized water. The structure (TiO2 nanotube array with diameter about 80-100 nm, wall thickness about 15-25 nm, and length 9 m) is characterized by field emission scanning electron microscope. The microstructure of the TiO2 nanotube array is characterized using X-ray diffraction. The effects of annealing condition on optical and electrical properties are studied. The electrical property is characterized by Keithley model 2450 source meter semiconductor characterization system in dark at room temperature. The voltaic batteries are assembled as a sandwiched structure (63Ni/TiO2 nanotube arrays film/Ti) using a radioisotope 63Ni plate and TiO2 nanotube array films. The experimental results show that the black TiO2 nanotube array film annealed at 450 ℃ in argon atmosphere could creates high visible-ultraviolet absorption due to a great many of oxygen vacancy defects generated in TiO2 nanotube array film. The oxygen vacancy signals are found by electron spin resonance. Compared with the planar structure, the nano-porous array structure has strong absorption to particles:most of the particles enter into the pores and are reflected or absorbed by the surface of the tube walls. With a 10 mCi 63Ni radiation source, the voltaic battery using black TiO2 nanotube array film can generate an open-circuited voltage of 1.02 V, a short-circuited current of 75.52 nA, and a maximum effective conversion efficiency of 22.48%.

Nanotube array-like WO3/W photoanode fabricated by electrochemical anodization for photoelectrocatalytic overall water splitting

Photoactive WO3 is attractive as a photocatalyst for green energy evolution through water splitting. In the present work, an electrochemical anodic oxidation method was used to fabricate a photo-responsive nanotube array-like WO3/W (NA-WO3/W) photoanode from W foil as a precursor. Compared with a reference commercial WO3/W electrode, the NA-WO3/W photoanode exhibited enhanced and stable photoelectrocatalytic (PEC) activity for visible-light-driven water splitting with a typical H2/O2 stoichiometric ratio of 2:1 and quantum efficiency of approximately 5.23% under visible-light irradiation from a light-emitting diode (λ = 420 nm, 15 mW/cm2). The greatly enhanced PEC performance of the NA-WO3/Wphotoanode was attributed to its fast electron–hole separation rate, which resulted from the one-dimensional nanotube array-like structure, high crystallinity of monoclinic WO3, and strong interaction between WO3 and W foil. This work paves the way to a facile route to prepare highly active photoelectrodes for solar light transfer to chemical energy.

Hydroxylation and dimerization of zearalenone: comparison of chemical, enzymatic and electrochemical oxidation methods

Investigations of the metabolic pathway of mycotoxins by microsomal techniques are often laborious, causing an increasing demand for easy and rapid simulation methods. Thus, the non-microsomal oxidation technique of electrochemistry coupled online to mass spectrometry (EC/MS) was applied to simulate phase I biotransformation of theFusarium mycotoxin zearalenone (ZEA). The obtained transformation products were identified by high resolution mass spectrometry (FT-ICR) and HPLC-MS/MS. Transformation products (TPs) from EC/MS were compared to those of other oxidative methods, such as Fenton-like and Ce(IV) reactions and metabolites derived fromin vitro assays (human and rat liver microsomes). Electrochemical oxidisation of ZEA was achieved by applying a potential between 0 and 2,500 mV vs Pd/H2 using a flow-through cell with a boron-doped diamond working electrode. Several mono-hydroxylated TPs were generated by EC/MS and Fenton-like reaction, which could also be found in microsomalin vitro assays. EC and Ce(IV) led to the formation of structurally different ZEA dimers and dimeric quinones probably connected over covalent biaryl C-C and C-O-C bonds. Although the dimerization of phenolic compounds is often observed in natural processes, ZEA dimers have not yet been reported. This is the first report on the formation of stable ZEA dimers and their related quinones. The tested non-microsomal methods, in particular EC/MS, could be useful in order to predict the biotransformation products of mycotoxins, even in cases where one to one simulation is not always feasible.

Two-Step Electrochemical Intercalation and Oxidation of Graphite for the Mass Production of Graphene Oxide.

Conventional chemical oxidation routes for the production of graphene oxide (GO), such as the Hummers' method, suffer from environmental and safety issues due to their use of hazardous and explosive chemicals. These issues are addressed by electrochemical oxidation methods, but such approaches typically have a low yield due to inhomogeneous oxidation. Herein we report a two-step electrochemical intercalation and oxidation approach to produce GO on the large laboratory scale (tens of grams) comprising (1) forming a stage 1 graphite intercalation compound (GIC) in concentrated sulfuric acid and (2) oxidizing and exfoliating the stage 1 GIC in an aqueous solution of 0.1 M ammonium sulfate. This two-step approach leads to GO with a high yield (>70 wt %), good quality (>90%, monolayer), and reasonable oxygen content (17.7 at. %). Moreover, the as-produced GO can be subsequently deeply reduced (3.2 at. % oxygen; C/O ratio 30.2) to yield highly conductive (54 600 S m-1) reduced GO. Electrochemical capacitors based on the reduced GO showed an ultrahigh rate capability of up to 10 V s-1 due to this high conductivity.

Metabolic engineering of Escherichia coli for the production of glyoxylate from xylose

Glyoxylate is an important chemical building block which is currently produced by chemical or electrochemical oxidation methods We herein described the achievement of microbial glyoxylate production from renewable biomass by metabolic engineering of Escherichia coli. The synthetic ribulose-1-phosphate pathway was expressed to produce glycolate from xylose. Additional genomic modifications including the inactivation of malate synthase genes aceB/glcB and glyoxylate carboligase gene gcl were performed to prevent the consumption of glyoxylate. The constructed strain was found to accumulate 0.13g/L glyoxylate in shake flask cultivations. Further overexpression of glycolate oxidase and catalase significantly improved glyoxylate production to 0.74g/L, which is the highest titer reported to date. These results demonstrate that microbial fermentation has a promising potential to manufacture glyoxylate from renewable feedstocks.

Hydrogen Permeation in Zirconium Using a Molten Salt Devanathan-Stachurski Electrochemical Cell

This paper explores whether the Devanathan-Stachurski method for the measurement of hydrogen permeation in metals can be extended to measure hydrogen diffusion zirconium at temperatures corresponding to the operating conditions of nuclear power plant. The investigation consisted of two steps, the selection of suitable electrodes and (molten salt) electrolytes for high temperature use, and the subsequent investigation of hydrogen charging and hydrogen electrochemical oxidation in the chosen electrolyte. An alternative electrochemical charging and oxidation method was devised using molten hydroxide (NaOH-KOH) as a suitable electrolyte at 250-300 °C.

Curcumin-quinone immobilised carbon black modified electrode prepared by in-situ electrochemical oxidation of curcumin-phytonutrient for mediated oxidation and flow injection analysis of sulfide

Curcumin, a natural pigment of the turmeric, has been widely used as a phytonutrient for various health benefits. There are several electrochemical reports relating to curcumin-metal complex modified electrodes for electroanalytical applications, and sensing of curcumin utilising the electrochemical behaviour of the phenolic site using different carbon-based chemically modified electrodes, in the literature. Herein, we report, a curcumin-quinone (Cur-Q) derivative immobilised carbon black (CB) modified glassy carbon electrode, designated as GCE/CB@Cur-Q, prepared by an in-situ electrochemical oxidation method, for efficient electrocatalytic oxidation and electrochemical sensing application of sulfide in pH2 KCl-HCl solution. The “as prepared” GCE/CB@Cur-Q showed a sharp redox peak at an apparent standard electrode potential, Eo′=0.55V vs. Ag/AgCl with surface excess and peak-to-peak potential values of 12.37×10−9molcm−2 and 19±5mV respectively. No such electrochemical behaviour was noticed when unmodified GCE was subjected to the electrochemical oxidation of curcumin. The existence of Cur-Q was confirmed by Liquid chromatography-mass spectrometer and in-situ electrochemical quartz crystal microbalance measurements. Amongst various carbon materials like CB, multiwalled carbon nanotube (MWCNT), single-walled carbon nanotube, oxygen functionalized MWCNT, graphite nanopowder, graphitised mesoporous carbon, carbon nanofiber, graphene oxide and activated charcoal investigated, CB was showed an excellent electrochemical reaction for the in-situ formation of Cur-Q. A highly sensitive electrocatalytic oxidation and sensing by amperometric i-t and flow injection analysis of sulfide at operating potential, 0.55V vs. Ag/AgCl with detection limit values (signal-to-noise ratio=3) of 2.4×10−6 and 7.12×10−6M respectively, without any interference from other biochemicals like uric acid, dopamine, nitrite, cysteine, NADH and H2O2, unlike the conventional chemically modified electrodes with serious interferences, have been demonstrated.

Synthesis of vanadia nanorod arrays and their novel applications as alco-sensors

Vanadia (V2O5) nanorod arrays were grown by oxidizing vanadium foil at five different voltages for 3h through electrochemical anodic oxidation method. Dense aligned nanorods with L/D ratio 4.75-4.88 (diameter D≈40–45nm and length≈190–220nm) were grown at the optimized voltage 55V. The dominant existence of V2O5 phase and its layered structure were verified by XPS and Raman spectrum analysis respectively. Linear I–V characteristic curve of the sensor based on V2O5 nanorod arrays confirms its Ohmic contact with the electrodes. Gas sensing investigations of the sensor reveals its n-type behavior with the average response magnitude of 6.13 in N2 atmosphere, which signifies the industrial application of the sensor in a gaseous atmosphere. The sensor shows remarkable static response towards ethanol with lower detection threshold of 800ppb and a maximum response magnitude of 7.27 at 500ppm. Based on variable resistance model, a suitable gas sensing mechanism is also established.

Flexible and Wearable All‐Solid‐State Supercapacitors with Ultrahigh Energy Density Based on a Carbon Fiber Fabric Electrode

AbstractWearable textile energy storage systems are rapidly growing, but obtaining carbon fiber fabric electrodes with both high capacitances to provide a high energy density and mechanical strength to allow the material to be weaved or knitted into desired devices remains challenging. In this work, N/O‐enriched carbon cloth with a large surface area and the desired pore volume is fabricated. An electrochemical oxidation method is used to modify the surface chemistry through incorporation of electrochemical active functional groups to the carbon surface and to further increase the specific surface area and the pore volume of the carbon cloth. The resulting carbon cloth electrode presents excellent electrochemical properties, including ultrahigh areal capacitance with good rate ability and cycling stability. Furthermore, the fabricated symmetric supercapacitors with a 2 V stable voltage window deliver ultrahigh energy densities (6.8 mW h cm−3 for fiber‐shaped samples and 9.4 mW h cm−3 for fabric samples) and exhibit excellent flexibility. The fabric supercapacitors are further tested in a belt‐shaped device as a watchband to power an electronic watch for ≈9 h, in a heart‐shaped logo to supply power for ≈1 h and in a safety light that functions for ≈1 h, indicating various promising applications of these supercapacitors.

Fabrication of chitosan/Au-TiO2 nanotube-based dry electrodes for electroencephalography recording

In this paper, we describe a method for fabricating dry electrodes for use in recording electroencephalograms (EEGs), which are based on the use of chitosan (Ch), gold (Au) particles, and titanium dioxide (TiO2) nanotube arrays deposited on titanium (Ti) thin sheets. The samples were characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and EEG signal collection. The TiO2 nanotube arrays were grown on the Ti thin sheet by an electrochemical anodic oxidation method. The Au particles were deposited on the bottom and surface layers of the TiO2 nanotube array using an electrochemistry-based multi-potential step technology. The fabricated dry Ch/Au-TiO2 electrodes have an efficient conversion interface for ion current/electron current, a high biocompatible contact surface, and a fast electron transfer channel. To confirm that the Ch/Au-TiO2 layer can be used in dry EEG electrodes, the impedance spectra of the electrodes in solution and skin were analyzed. The mean impedance values for skin were found to be approximately 169±33.0kΩ at 2.15Hz and 67.4±8.9kΩ at 100Hz. In addition, EEG signals from the forehead and sites with hair were collected using both the dry Ch/Au-TiO2 electrode and a wet Ag/AgCl electrode for comparison purposes. It was found that high quality EEG signal recordings could be obtained using the dry electrodes. The fact that electrolytes are not required means that the electrodes are suitable for use in long-term bio-potential testing.

High-performance wearable supercapacitors fabricated with surface activated continuous filament graphite fibers

Abstract Generally, carbon or graphite fibers (GFs) are used as the supporting materials for the preparation of flexible supercapacitors (SCs) by assembling various electrochemically active nanomaterials on them. A facile and rapid electrochemical oxidation method with a voltage of 3 V in a mixed H2SO4-HNO3 solution for 2–15 min is proposed to active continuous filament GFs. Detailed structural characterization, SEM, TEM, XRD, Raman and XPS demonstrate that the GFs-8 (oxidized for 8 min) possessing high specific surface area which provided numerous electrochemical sites and a large number of oxygen-containing functional groups producing pseudocapacitance. Cyclic voltammetric (CV), galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy (EIS) are conducted to test the capacitive of GFs and activated GFs. The capacitance of GFs-8 reaches as high as 570 mF cm−1 at the current density of 1 mA cm−1 in LiCl electrolyte, a 1965-fold enhancement with respect to the pristine GFs (0.29 mF cm−1). The fabricated fiber solid-state supercapacitors (SSCs) provide high energy density of 0.68 mWh cm−3 at the power density 3.3 W cm−3 and have excellent durability with 90% capacitance retention after 10000 cycles. In addition, such fiber SSCs features flexibility and mechanical stability, which may have wide applications in wearable electronic devices.

Exfoliation of LiNi1/3Mn1/3Co1/3O2 into Nanosheets Using Electrochemical Oxidation and Reassembly with Dialysis or Flocculation.

Two-dimensional (2D) materials such as nanosheets are increasingly attracting attention for applications in energy storage and conversion. Many conventional battery compounds have layered structures, which can facilitate the exfoliation of these materials into nanosheet morphologies. In this work, LiNi1/3Mn1/3Co1/3O2 (NMC) particles were exfoliated into nanosheets using an electrochemical oxidation method enabled by the intercalation of tetraethylammonium cations into the interlayer space. The exfoliated materials were monolayer or double-layer nanosheets with hexagonal shapes and sizes of <50 nm. Two different methods were used to reassemble the nanosheets into NMC particles: (1) a slow, dialysis-based approach and (2) direct flocculation. Characterization of the NMC materials at different stages in the exfoliation and reassembly processes was performed using compositional analysis, X-ray diffraction, electron microscopy, and electrochemical methods. The dialysis reassembly method allowed for the restacking of the nanosheets into faceted, hexagonally shaped nanoplatelets, and the flocculation approach yielded only ill-defined particles. The differences in the observed potential-dependent redox behavior and electrochemical cycling characteristics are attributed to the role of the reassembly method in the formation of phase-segregated domains, with the particles reassembled using the dialysis approach displaying the best performance.

Electrochemical Oxidation of Psychoactive Pharmaceutical Caffeine in Aqueous Medium Using RuO2/IrO2/TaO2 Coated Titanium Anode

Caffeine is one of the most widely used psychoactive drug in the world .Apart from being commonly used in beverages (soft drinks, tea and coffee), it is one of the components of painkillers, medication against migraine, fatigue, drowsiness and breathing problems, etc. Unlike other psychoactive substances, utilization of caffeine is legal in most countries. It is generally recognized as safe at usual moderate doses, though it becomes toxic in excessive amounts. Several clinical studies showed a relation between caffeine and anxiogenic effect and/or panic disorders. Its consumption is also associated with an overall lower risk of malignant growth like hepatocellular, endometrial or colorectal cancer. Still the effect of caffeine and its environmental degradation products on aquatic living species is not known. Therefore, as a preventive measure a development of an effective removal method is needed. Electrochemical oxidation method has many advantages such as low cost, simplicity, and amenability to miniaturization. Selective electrochemical oxidation for the caffeine in aqueous medium using RuO2/IrO2/TaO2 coated titanium anode has been investigated. The effect of the process variables, such as initial pH, current density, processing time, concentration of the electrolyte and anode materials, on the degradation of caffeine was studied. During the various stages of electrolysis, parameters such as COD, TOC and UV-Vis spectra were examined and discussed. The maximum chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiency of 96.9% and 100% was achieved at pH 7, operated at the current density of 5.1 mA/cm2, electrolyte (Na2SO4) concentration of 0.1 M and at 240 min of electrolysis using RuO2/IrO2/TaO2 coated titanium anode. Electrochemical oxidation process could effectively reduce the COD and TOC from the Caffeine in aqueous medium. The degradation of the caffeine was confirmed using FT-IR, HPLC and GC-MS analysis. The degradation pathway proposed.

Interaction between NiOx and MWСNT in NiOx/MWСNTs composite: XANES and XPS study

The current work presents the investigation of the interaction between NiOx and multi-walled carbon nanotube (MWCNTs) sidewall in NiOx/MWCNT nanocomposite, synthesized by electrochemical metal oxidation and dispersion method using the near edge X-ray absorption fine structure (XANES) and X-ray photoelectron spectroscopies. Scanning electron microscopy (SEM) illustrated that formation of the NiOx/MWCNT composite leads to decreasing of the NiOx sheets size and their dispersion among nanotubes. Comparison of the C K-edge XANES spectra of the initial high-purified MWCNTs with NiOx/MWCNTs indicates significant shape changes of the nanocomposite spectrum. Changes in π resonance and inter-resonance region of C K-edge XANES spectrum showed the appearance of new chemical bonds in the carbon nanotubes as result of formation of NiOx/MWCNTs nanocomposite, associated with partial chemical interaction of NiOx with CNT walls. The chemical state of Ni in the composite compound is 2+ and there is Ni with different oxygen surroundings in the NiOx/MWCNT nanocomposite.

Studying the growth of carbon nanotubes on carbon fibers surface under different catalysts and electrochemical treatment conditions

ABSTRACTA special electrochemical anodic oxidation (EAO) method was applied to modify the surface of carbon fibers (CFs) with fatty alcohol polyoxyethylene ether phosphate (O3P), triethanolamine (TEA), fatty alcohol polyoxyethylene ether ammonium phosphate (O3PNH4), and ammonium bicarbonate (NH4HCO3) used as the electrolyte respectively. Then different catalysts, including Ni, Co, and Cu, were used to catalyze the growth of carbon nanotubes (CNTs) on the surface of CFs. The variation regulation of structure and property of CNTs on CFs surface was investigated by different methods. The results showed that the optimal effect of surface modification of CFs was achieved when O3PNH4 served as an electrolyte and the optimal electrochemical treatment intensity (ETI) was 100C/g. Also, with temperature variety, there are different microstructure changes for CNTs that adopt different catalysts. Through the experiment, a uniform catalyst coating was obtained on the surface of CFs after reduction process, which laid the foundation for the growth of uniform and regular CNTs.