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1.
《Electrochemistry communications》2008,10(12):1823-1826
LiFePO4/mesocarbon microbead (MCMB) cells of which the carbon electrodes were, respectively, coated with different metal layers were characterized for their charge/discharge cycle performance at 55 °C. The examined metals included Au, Cu, Fe, Ni, Co, and Ti, and the superficial layers were 30–50 nm in thickness and deposited by vacuum sputtering. It was found that the presence of a either Au or Cu layer remarkably reduces capacity fading, while the rest metals only accelerate fading. There was observed a consistent trend between the capacity fading rate and the amount of the soild-electrolyte-interphase (SEI) deposition; the faster the capacity fading, the greater amount of SEI materials appearing on the surface of cycled carbon electrode. Microscopic and composition analyses indicates that the superficial Au and Cu layers act as a sieve to collect the Fe ions that result form erosion of LiFePO4 before they diffuse into the interior of the carbon electrode, and that the so-deposited Fe particles do not show the tendency to catalyze the SEI formation, as in contrast to those directly deposited on the carbon surfaces. 相似文献
2.
The objective of this work is to explore approaches to enhance electrochemical signals through sequential deposition and capping of gold particles. Gold nanoparticles are electrodeposited from KAuCl4 solution under potentiostatic conditions on glassy carbon substrates. The number density of the nanoparticles is increased by multiple deposition steps. To prevent secondary nucleation processes, the nanoparticles are isolated after each potentiostatic deposition step by self‐assembled monolayers (SAMs) of decanethiol or mercaptoethanol. The increasing number of particles during five deposition/protection rounds is monitored by assembling electroactive SAMs using a ferrocene‐labeled alkanethiol. A precise estimation of the surface area of the gold nanoparticles by formation of an oxide layer on gold is difficult due to oxidation of the glassy carbon surface. As an alternative approach, the charge flow of the electroactive SAM is used for surface measurement of the gold surface area. A sixfold increase in the redox signal in comparison to a bulk gold surface is observed, and this increase in redox signal is particularly notable given that the surface area of the deposited nanoparticles is only a fraction of the bulk gold surface. After five rounds of deposition there is a gold loading of 1.94 μg cm?2 of the deposited nanoparticles as compared to 23.68 μg cm?2 for the bulk gold surface. Remarkably, however, the surface coverage of the ferrocene alkanethiol on the bulk material is only 10 % of that achieved on the deposited nanoparticles. This enhancement in signal of the nanoparticle‐modified surface in comparison to bulk gold is thus demonstrated not to be attributable to an increase in surface area, but rather to the inherent properties of the surface atoms of the nanoparticles, which are more reactive than the surface atoms of the bulk material. 相似文献
3.
Van Berkel GJ 《Journal of mass spectrometry : JMS》2000,35(7):773-783
The electrospray ion source is an electrolytic flow cell. Electrolytic reactions in the electrospray emitter maintain the production of charged droplets by this ion source that contain an excess of ions of one polarity. These redox reactions necessarily change the composition of the solution that initially enters the emitter. As a result, the ions ultimately observed in the gas phase by electrospray mass spectrometry (ESMS) may be substantially influenced by both the nature and extent of these electrochemical reactions. It is demonstrated in this paper that Ag(+), Cu(2+) and Hg(2+) ions in solution can be electrolytically reduced and deposited as the respective metals on to the surface of the high-voltage contact in the electrospray emitter in negative ion mode electrospray. The deposited metals are shown to be liberated from the surface by switching the electrospray high-voltage polarity to operate in the positive ion mode. The deposited metals are oxidized in positive ion mode, releasing the metal ions back into solution where they are detected in the electrospray mass spectrum. In a semi-quantitative analysis, it was found that up to 50% of the Ag(+) in a 2.5 microM solution was deposited on the high-voltage contact of the emitter as the solution flowed through the emitter. Deposition of Cu(2+) and Hg(2+) was less efficient. These data illustrate that in the analysis of metals by ESMS, one must be aware that both the concentration and form of the metals may be altered by electrochemical processes in the emitter. Hence reduction or oxidation of metals in the electrospray emitter, which may remove ions from solution, or change metal valence, would be expected to impact both quantitative metal determinations and metal speciation attempts using ESMS. 相似文献
4.
5.
Substrate-enhanced electroless deposition of metal nanoparticles on carbon nanotubes 总被引:3,自引:0,他引:3
By simply supporting carbon nanotubes with a metal substrate of a redox potential lower than that of the metal ions to be reduced into nanoparticles, we have developed a facile yet versatile and effective substrate-enhanced electroless deposition (SEED) method for functionalizing nanotubes with a large variety of metal nanoparticles, including those otherwise impossible by more conventional electroless deposition methods, in the absence of any additional reducing agent. The nanotube-supported metal nanoparticles thus produced are electrochemically active, and the newly developed SEED process represents a significant advance in functionalization of carbon nanotubes with metal nanoparticles for a wide range of potential applications, including in advanced sensing and catalytic systems. 相似文献
6.
Adsorption of acetone on active carbon and active carbon supported metals (Ni, Cu, Zn and Cd) have been studied as a function of temperature. Thermodynamic parameters such as G
0, H
0, and S
0 are calculated from virial and Langmuir isotherm expressions. It is observed that active carbon supported metals have more adsorption affinity for acetone as compared to active carbon. Results show that the increase in adsorption affinity for active carbon supported metals is not due to configurational factors affecting the entropy of adsorption, but because of enhanced enthalpy of adsorption. XRD spectra show that active carbon supported metals adsorbents are amorphous and metal residues are present on the surface of active carbon in its reduced form. From adsorption data, isosteric heats and molar entropies of adsorption were calculated as a function of coverages and temperature. The values of isosteric heats of adsorption were found to be higher for active carbon supported metals, which may be due to the chemisorption of adsorbate molecules with metal sites present on the surface of active carbon. The extent of coordination of adsorbate molecules with metal sites is discussed on the basis of the acidic character of metal. 相似文献
7.
A. A. Vedenyapin M. D. Baturova G. I. Ioseliani G. Kh. Areshidze 《Russian Chemical Bulletin》1997,46(1):76-80
The anodic oxidation of the carbon felt Carbonetcalon results in the formation of surface defects which serve as centers of
strong adsorption of PdII, NiII, and CuII ions. The electrochemical reduction of adsorbed ions makes it possible to obtain metallic catalysts, which undergo multiple
redox cycles without loss of metal. The catalysts are characterized by high dispersity of the reduced phase, high adsorption
capacity with respect to hydrogen, and 100% selectivity in hydrogenation of acetophenone.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 81–85, January 1997 相似文献
8.
Bismuth film electrodes are widely used for determination of heavy metal ions in acidic solutions, while alkaline solutions are rarely employed. We have compared the deposition of Bi(III) and Pb(II) on a Nafion-coated glassy carbon electrode in alkaline and acidic solutions. The results indicate that both Bi(III) and Pb(II) can be deposited in either alkaline or acidic solution, but the quantity of Pb(II) deposited in alkaline solution is less than that in acidic solution. The modified electrode was used to determine heavy metal ions in both alkaline and acidic solutions, and the results of the method agree well with those of atomic absorption spectroscopy. 相似文献
9.
V. V. Novikova S. P. Starodubova M. Yu. Chaika T. A. Kravchenko 《Russian Journal of Electrochemistry》2013,49(3):278-284
Silver particles are formed by electrochemical deposition on the carbon electrode surface. It is found that the deposition process occurs according to the progressive nucleation mechanism, which results in formation of silver particles with the size of 95 to 190 nm as dependent on the electrodeposition time. The values of silver particle size and support surface coverage by metal obtained on the basis of microphotographs indicate that cathodic polarization in the presence of dissolved oxygen results in particle size redistribution due to the reaction of silver particle dissolution with further deposition simultaneously with oxygen electroreduction. The reaction of molecular oxygen electroreduction on a carbon electrode with deposited dispersed silver occurs via a mixed two- and four-electron mechanism. The observed limiting reaction current is of diffusion nature. 相似文献
10.
Catalytic graphitization of PAN-based carbon fibers by spontaneously deposited manganese oxides 总被引:1,自引:0,他引:1
A simple method for the spontaneous deposition of manganese oxides on the surface of polyacrylonitrile (PAN)-based carbon
fibers by a direct redox reaction between carbon fibers and permanganate ions is described. Catalytic graphitization of the
PAN-based carbon fibers coated with manganese oxides was investigated by X-ray diffraction, Raman spectroscopy, and scanning
electron microscopy. The results indicate that the graphitization of the PAN-based carbon fibers was accelerated in the presence
of the manganese oxides even at the relatively low temperature of 1,600 °C. 相似文献
11.
12.
A procedure has been developed for the determination of the concentration of heavy metals (Pb, Mn, Cu, Ni, Zn, and Cd) in atmospheric air by atomic emission spectrometry with gas-discharge sampling onto the end of a standard carbon electrode. A design of a two-section sampler is proposed; the sampler provides the rapid determination of deposition factors for heavy metals contained in aerosol particles deposited onto the end of a carbon electrode. Examples of determining metal concentrations in a model sample of air and in atmospheric air and determination limits of metals deposited onto the end of a carbon electrode are given. 相似文献
13.
《中国化学快报》2023,34(7):107767
Compared with solid alkali metal anodes (Li, Na, K), liquid metal anodes (LMAs) could enable high-energy batteries due to their unique advantages, such as self-healing property and no dendrites. Among LMAs, liquid Na-K alloy anode has become a hotspot due to its high theoretical capacity, low redox potential and formation at room temperature (RT). However, it is challenging to utilize liquid Na-K alloy directly and independently as an electrode; and the high surface tension makes it more difficult to immerse into porous current collectors at RT. Herein, an amorphous hollow carbon film (AHCF) consisting of hollow spheres with significant surface defects has been designed to quickly infiltrate Na-K liquid alloy into the hollow carbon film at RT, forming a composite electrode (Na-K@AHCF). The symmetric cell with Na-K@AHCF could exhibit a cycle lifespan up to 400 h at 0.1 mA/cm2 and achieve stable stripping/deposition even at 5 mA/cm2. When matching with cathode material of sulfurized polyacrylonitrile (SPAN), the obtained K-S full cell exhibits good cycle stability and rate performance. 相似文献
14.
《Electrochemistry communications》2002,4(2):193-196
In this preliminary note, carbon paste electrodes (CPEs) plated with a bismuth film are presented. The bismuth film can be generated onto the carbon paste surface either from an external plating solution or in situ; the latter being performed in two ways: (i) as a spike of the Bi3+ ions to the solution or (ii) via modifying the carbon paste with solid bismuth oxide (5% m/m). As shown on selected examples, bismuth-film-plated CPEs exhibit a good performance in voltammetric stripping analysis of some heavy metals such as Pb, Cd, and Zn. 相似文献
15.
《Journal of Electroanalytical Chemistry》1987,217(2):385-395
It is shown that the underpotential deposition (UPD) and dissolution of monolayers of Pb and Tl onto Ag surfaces roughened in a controlled oxidation-reduction cycle produces a Ag surface which shows diminished surface enhanced Raman scattering (DSERS). Significantly enhanced Raman spectra can still be obtained from electrodes covered by complete UPD and overpotential deposited (OPD) layers of the metals. Correct choice of electrolytes for the UPD of the metal reduces the loss of enhanced Raman scattering; chloride ions, constituents of many electrolytes used in the investigation of surface enhanced Raman scattering (SERS), are shown to be especially active in causing the loss of SERS. 相似文献
16.
We employ Nafion-mixed carbon dots (CDs) and low-cost screen-printed carbon electrodes (SPCEs) as foundation matrices for the fabrication of electrochemical biosensors. The NH2 and COOH functional groups present on the SPCE surface after Nafion/CDs deposition allow for pyrophosphate ions (PPis) collection. Using Fe(CN)63− as the electrochemical mediator, the SPCE-Nafion/CDs are applied to the detection of aqueous PPi by square wave voltammetry. Between 50 and 1 μM, a linear connection is established between the square wave voltammetry current and the PPi concentration. The limit of detection is determined to be 1.01 μM, and recoveries of 113% (±1.9%) and 108% (±3.9%) are achieved for human urine samples spiked with 6 and 3 μM of PPi, respectively. Furthermore, this PPi assay is suitable for the usage of complicated urine matrices without the inclusion of heavy metals. We anticipate that this unique approach will be beneficial for PPi level monitoring in urine during therapeutic treatments of illnesses and malignancies. 相似文献
17.
Anand I. Bhatt Alan M. Bond Jie Zhang 《Journal of Solid State Electrochemistry》2007,11(12):1593-1603
The electrochemical reduction of Pb2+ has been studied in the ‘distillable’ ionic liquid DIMCARB (a mixture of adducts of dimethylamine and carbon dioxide, comprising
both neutral and ionic moieties). Voltammetric results show that Pb2+ is reduced in a single step to form Pb metal via a nucleation and growth mechanism on a glassy carbon electrode. Ex situ
powder X-ray diffraction studies on deposited lead show the presence of both α- and β-PbO2, as well as elemental lead, suggesting the finely deposited lead particles are in an active rather than passive state. Chronamperometric
and scanning electron microscope measurements show that the nucleation and growth follows a progressive nucleation mechanism
on glassy carbon. Large peak–peak separations for the Pb reduction and oxidation are consistent with this mechanism and do
not suggest electrochemical reversibility. However, experiments with co-deposition of Hg show that this irreversibility is
a result of deposition onto a solid glassy carbon surface rather than a solvent effect. The diffusion coefficient of Pb2+ in DIMCARB has been calculated to be 1.8±0.4×10−7 cm2 s−1.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.
This work is dedicated to Piero Zanello on the occasion of his 65th birthday in recognition of his numerous contributions
to inorganic electrochemistry. 相似文献
18.
A. A. Mikhaylova E. K. Tusseeva A. Yu. Rychagov Yu. M. Vol’fkovich A. V. Krestinin O. A. Khazova 《Russian Journal of Electrochemistry》2010,46(11):1280-1288
Composites of functionalized single-wall carbon nanotubes and polyaniline are deposited onto electrodes by in situ electrochemical
polymerization. Their electrochemical behavior and differential capacitance are studied by cyclic voltammetry, electrochemical
impedance spectroscopy, and chronovoltamperometry. The differential capacitance of the composite electrode exceeds that of
pure polyaniline film deposited onto electrode, which can be explained by the nanotubes’ loosening effect on the polyaniline
structure. The composite-electrode capacitance is as large as 1000 F g−1 or higher. Thus obtained composite films were used as a support for deposited platinum-ruthenium catalyst. The Pt-Ru structure
and catalytic properties in the methanol oxidation reaction are studied. It is shown that the specific current of methanol
oxidation at Pt-Ru is larger by a factor of 7–15 than those measured when pure polyaniline, pure carbon nanotubes, or standard
Vulcan XC-72 carbon black are used as supports. It is found that the catalytic activity is the same for all studied supports,
provided the current is reduced to the unit of Pt-Ru true surface area. Thus, the observed large catalytic effect is associated
with the structure and high dispersivity of the electrodeposited metals incorporated to the single-wall carbon nanotubes-polyaniline
composite. 相似文献
19.
Thomasin C MillerJames A Holcombe 《Analytica chimica acta》2002,455(2):233-244
Two biologically based ligands, cysteine (Cys) and poly-l-cysteine (PLCys), were coupled with Carbopack-X, a commercially available porous carbon surface after acid activation, through simple cross-linking techniques. The resulting Cys-X and PLCys-X systems are effective for metal binding with capacities in the range of 1-25 μmol metal/g column, depending on the metal tested. Both columns demonstrate similar selectivity for the soft and moderately soft acid metals such as Cd2+, Cu+, and Pb2+, probably as a result of the soft basic character of the thiol ligand side chains, and exhibit minimal binding of the harder groups IA and IIA metals. Even though PLCys-X and Cys-X displayed similar strong and weak binding characteristics, the PLCys-X system contained stronger binding sites than those possessed by Cys-X. The strongest site displayed by Cys-X has a binding constant of 1×109, with the ability to compete for metal with moderately strong ligands such as ethylenediamine. However, the strongest PLCys-X site possessed a binding constant of about 1013, with the ability to compete for metals bound by very strong ligands such as EDTA. Both systems gave quantitative release of bound metals upon exposure to acid. Exposing the thiol-rich ligands to chemical reducing or oxidizing environments altered the metal binding characteristics of both columns, with at least a 50% decrease in metal binding on the oxidized columns due to thiol binding sites because of disulfide bond formation. 相似文献
20.
Chengbing Wang Xiaoming Ling Jing Shi Rongbin Xia 《Surface and interface analysis : SIA》2014,46(8):550-555
A–C:H (hydrogenated amorphous carbon) films were deposited by pulsed direct‐current (d.c.) plasma enhanced chemical vapor deposition on silicon substrates. This study investigated the structural and mechanical evolution of the as‐deposited films with fullerene‐like nanostructure. The results showed that pulsed d.c. negative bias (?500 ~ ?1000 V) signally influenced the growth rate, hardness, surface roughness, sp3 content, and friction behavior of the films. As the pulsed d.c. negative bias voltage increased, the sp3 content, surface roughness, hydrogen content and the friction coefficient of the films decreased; however, the growth rate and the hardness increased. The films deposited at ?1000 V with fullerene‐like microstructure display a nanohardness of about 19.7 GPa and the smallest friction coefficient (~0.06). The evolution on mechanical and structural properties of the films are explained by the a–C:H growth mechanism based on the interaction on plasma‐surface interface and the subsurface reactions in the film. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献