Glassy Carbon Anode Research Articles

Nanostructured polyaniline-coated anode for improving microbial fuel cell power output

AbstractAn approach for improving the power generation of a dual-chamber microbial fuel cell by using a nanostructured polyaniline (PANI)-modified glassy carbon anode was investigated. Modification of the glassy carbon anode was achieved by the electrochemical polymerisation of aniline in 1 M H2SO4 solution. The MFC reactor showed power densities of 0.082 mW cm−2 and 0.031 mW cm−2 for the nano- and microstructured PANI anode, respectively. The results from electron microscopy scanning confirmed formation of the nanostructured PANI film on the anode surface and the results from electrochemical experiments confirmed that the electrochemical activity of the anode was significantly enhanced after modification by nanostructured PANI. Electrochemical impedance spectroscopic results proved that the charge transfer would be facilitated after anode modification with nanostructured PANI.

Electrochemical study on various types of anode materials in LiCl–KCl eutectic salt used in the electro-winning process

The electrochemical behaviors of the molybdenum, graphite, and glassy carbon anode have been observed during the electrolysis of uranium chloride in an UCl3–LiCl–KCl molten salt. The cyclic voltammogram data of the molybdenum anode showed that Mo anode could be corroded by the formation of Mo compounds or its dissolution. However, the experimental data of the graphite and the glassy carbon anode showed that the chlorine evolution started from 1.2 V and the anode potential remained stable during uranium electrolysis. Therefore, the graphite and glassy carbon may be used as an inert anode in the electro-winning process of pyroprocessing.

Salt clean-up for recycling by electrolysis with a cathode-perforated ceramic container assembly

Pyroprocessing is a promising way for the recovery of actinide elements from the used nuclear fuel. Electro-refining is a key technology of pyroprocessing and the electro-refining is generally composed of two recovery steps—deposit of uranium onto a solid cathode and the recovery of actinide elements by a liquid cathode. After the electro-refining process, it is necessary to remove the solutes from the molten salt for the salt regeneration. In this study, it was attempted to clean up a molten salt with a solid cathode- perforated ceramic container assembly and a glassy carbon anode. LiCl–KCl eutectic salt was used as a medium of the electrolytic bath. Uranium and cerium were used as solutes, where uranium was used as a surrogate for the actinide elements. The initial contents of uranium and cerium in the salt were varied in the range of 0–5 wt%. Electrolysis experiments were carried out by passing a constant current between the anode and cathode at 500 °C. The solute contents were measured using ICP-AES spectroscopy. The initial cathode potential was about −1.6 V. This value decreased with increasing time in the salt. The solutes in the saline phase were successfully recovered onto the cathode.

A high pressure single-pass high-conversion electrochemical cell for intensification of organic electrosynthesis processes

The anode oxidation of 4-methoxytoluene (4-MT) to 4-methoxybenzyl dimethylacetal (4-MBDMA) in methanol is used as a test reaction for the study of a microchannel electrochemical reactor operated continuously in a single-pass high-conversion mode. The cell consists of two stainless steel cathodes, grooved with 100μm deep channels surrounding a flat glassy carbon anode. Pressures up to 20 bars are applied in the cell in order to reduce the volumetric flow rate of the cathodically produced hydrogen. Both the narrow gap and the operation under pressure lead to an enhancement of the electrolytic conductivity of the cell and make it possible to operate with concentrated solutions, with high current densities and with a very low supporting electrolyte concentration (i.e. 0.01M KF).The cell performance is discussed in terms of cell voltage, reactant conversion, material and current efficiency and finally selectivity in 4-MBDMA. The effect of inlet reagent concentration, pressure, flow-rate and temperature are investigated. Best performance is obtained with 0.5M 4-MT at 5 bars and 45°C: for a 90% conversion, selectivity and current efficiency attain, respectively, 92% and 85%. The high pressure, single-pass high-conversion cell exhibits in this case a space time yield 5–10 times higher than the current industrial process, with a significantly lower concentration of the supporting electrolyte.

TEMPO mediated oxidation of carbohydrates using electrochemical methods

The oxidation of some readily available carbohydrates was investigated in aqueous medium using a catalytic amount of 2,2,6,6-Tetramethyl-1-piperidinyl-oxy (TEMPO) as redox mediator. The regeneration of oxoammonium (active form) was electrochemically performed in alkaline medium at a glassy carbon anode and at controlled potential (0.5 V vs. AgCl/Ag). The primary alcohol groups of the carbohydrates without free aldehyde group, were selectively oxidized to the corresponding sodium uronate with high Faradaic yields. The presence of free aldehyde or hemiacetal groups leads to a decrease in selectivities towards uronic acids and increases the amount of by-products.

Electrochemical preparation of colloidal fluorescent graphite

Colloidal graphite having nano- and microparticles and exhibiting fluorescence properties was prepared by the destruction of the glassy carbon anode in the electrolyte containing hydrochloric acid and α-olefin C16-C18.

Electrochemical oxidation of tertiary phosphines in the presence of camphene

Anodic oxidation of tertiary phosphines (tripropyl-, tributyl-, and triphenylphosphine) in the presence of a bicyclic alkene (camphene) on a platinum and a glassy carbon electrodes was studied. For the first time the voltammetric characteristics of the process of camphene anodic oxidation were obtained. The electrochemical reactions with alkyl and aromatic phosphine were found to be dissimilar. The results of preparative electrooxidation of trialkylphosphines showed that in the course of electrolysis the tertiary phosphine cation-radicals generated on the anode enter into two concurrent reactions: (1) with the parent phosphine to form eventually trialkylphosphonium salts and trialkylphosphine oxides presumably as complex compounds and (2) with camphene to form trialkylcamphenylphosphonium salts and probably phosphonium salts with a monocyclic substituent. Preparative electrochemical oxidation of triphenylphosphine in the presence of camphene affords almost exclusively either triphenylphosphine oxide (in the experiment with platinum anode) or the triphenylphosphine oxide complex with perchloric acid (at the electrolysis on a glassy carbon anode).

Performance of a Glucose/O2 Enzymatic Biofuel Cell Containing a Mediated Melanocarpus albomyces Laccase Cathode in a Physiological Buffer

AbstractWe report on the performance of a prototype glucose/O2 biofuel cell in a physiological buffer. The cell consists of cathode based on Melanocarpus albomyces laccase (with a reported T1 copper redox potential of + 0.26 V vs. Ag/AgCl) co‐immobilised with an osmium redox polymer mediating film on glassy carbon (GC) separated by a Nafion 117 membrane from a GC anode in anolyte of glucose oxidase, N,N,N′,N′‐tetramethyl‐p‐phenylenediamine (TMPD) as a mediator, all immersed in pH 7.4 phosphate buffer solution containing 0.15 M NaCl and dissolved oxygen, thermostated at 37 °C, mimicking physiological conditions. Two osmium redox polymers are employed for cathodic mediation: [Os(2,2′‐bipyridine)2(polyvinylimidazole)10Cl]+/2+ (E°′ 0.22 V vs. Ag/AgCl) and [Os(4,4′‐dichloro‐2,2′‐bipyridine)2(polyvinylimidazole)10Cl]+/2+ (E°′ 0.35 V vs. Ag/AgCl). Power outputs of 52 μW cm–2 at 0.21 V and 17 μW cm–2 at 0.34 V were obtained for assembled fuel cells containing the respective redox polymer‐mediated laccase cathodes, illustrating the increased power obtained as a result of higher biocatalytic efficiency using a redox polymer with redox potential tailored for the enzyme.

Water electrolysis: an excellent approach for the removal of water from ionic liquids

An electrochemical system based on platinum cathode and glassy carbon anode was assembled for a successful removal of water from ionic liquids via the water electrolysis strategy.

Tungsten Chemistry in Alkali Chloride Melts

Speciation of tungsten in alkali chloride melts (based on NaCl-2CsCl, NaCl-KCl and 3LiCl-2KCl mixtures) was studied between 550 and 750◦C using electronic absorption spectroscopy. OnlyW(IV) and W(V) chloro and oxychloro species can be stabilized under the conditions studied. Tungsten(IV) chloride ions are very sensitive to oxide/hydroxide impurities present in the melt. Anodic dissolution ofWmetal at anodic current densities in the range of 0.005 - 0.1 A/cm2 produces only [WCl6]2− ions that can be electrochemically (on a glassy carbon anode) oxidized to [WCl6]−. Small amounts of oxide ions present in the melt result in a gradual conversion of W(IV) chloro species intoW(IV) oxychloro species. In the presence of O2 in the atmosphere [WCl6]2− is oxidized into the tungsten(V) species [WOCl5]2−. Dissolution of tungsten hexachloride, WCl6, in an NaCl-2CsCl melt initially yields [WCl6]2− (due to disproportionation). Reaction of metallic tungsten with Pd(II)-containing melts results in the formation of [WCl6]2− species. The main spectroscopic parameters of [WCl6]2− and [WCl6]− complex ions were calculated.

Regioselective Anodic Fluorination of α-(Arylthio)benzylphosphonate Esters, α-(Arylthio)methylphosphonate Esters and Their Analogues

Regioselective anodic α-fluorination of α-(arylthio)benzylphosphonate esters and [(arylthio)methyl]- and [(heteroaryl­thio)methyl]phosphonate esters was successfully carried out at a glassy carbon anode or platinum anode in dimethoxyethane and ­nitromethane to provide the corresponding α-fluorophosphonate ­esters in excellent to moderate yields.

Influence of the Anode on the Degradation of the Additives in the Damascene Process for Copper Deposition

The influence of both soluble and insoluble anodes on the kinetics and morphology of the copper deposit in the damascene process was investigated by voltammetry and impedance techniques. A plating bath known to provide conformal superfilling of trenches and vias in the microelectronic industry was used. It was shown that the use of a glassy carbon anode leads to faster degradation of the plating bath which is detrimental to the copper deposit. A copper anode decreases the aging rate by limiting the anodic potential compared to the glassy carbon anode where high anodic potentials prevail during the copper deposition process.

Electrooxidation of activated α,ω-diols to cyclic tetramethylene acetals of the corresponding dials

Activated α,ω-diols such as ethylene glycol 1a, 1,3-propanediol 1b, but-2-ene-1,4-diol 1c and hexa-2,4-diyne-1,6-diol 1d can be converted into cyclic tetramethylene acetals of the corresponding α,ω-dials ( 2a– d) in 70% yield by a simple anodic oxidation in dry tetrahydrofuran on a glassy carbon anode. Glycerol 3 when subjected to similar anodic oxidation gave a structure 4 containing three seven-membered 1,3-dioxepane rings.

Electrochemical Oxidation of But-2-yne-1,4-diol

But-2-yne-1,4-diol (1) was electrochemically oxidized on glassy carbon anode in a dry THF solution containing a quaternary ammonium salt, in an undivided cell giving di(1,3-dioxepan-2-yl)ethyne (5) in 80% yield. The electrochemically generated dialdehyde intermediate is assumedly acetalized in a fast reaction with THF. Dimerized product 6 was isolated in 85% yield after electrooxidation of diol 1 in dry 1,2-dimethoxyethane under similar conditions.

Safety characteristics of Li-ion batteries evaluated byin situ measurement techniques

Li-ion batteries hold an important place in the field of high power batteries because of their high open circuit voltage and associated high energy density. However, the safety is less satisfactory; therefore, the study of the factors that affect the safety of Li-ion batteries has much meaning to the safety design. In this paper, a set of apparatus was developed forin situ measurements, and several commercial materials including electrolyte, separator and electrode materials for Li-ion batteries were investigated by thein situ method. The results showed: 1) The electrolyte vapor pressure is influenced significantly by the component with low boiling point and increases rapidly with the increasing of temperature; 2) the shutdown of separator occurs at around 135°C and the impedance increases approximately by two orders of magnitude; 3) carbon anode materials affect the most the volume changes of the cell, and the change for a graphite anode is much greater than that of a glassy carbon anode.

Anodic Preparation of [Re2Cp2(CO)6]2+: A Dimeric Dication that Provides the Powerful One-Electron Oxidant [ReCp(CO)3]+

The half-sandwich piano-stool compounds Re(eta5-C5R5)(CO)3 (1, R = H; or 2, R = Me) are oxidized to the corresponding 17-electron Re(II) cations at glassy carbon anodes in CH2Cl2/[NBu4][B(C6F5)4]. Despite the very strongly positive E1/2 values of the couples (1.16 V for 1/1+ and 0.91 V for 2/2+ vs ferrocene/ferrocenium), the radical cations are persistent in this medium and exist in equilibrium with the corresponding dimeric dications, which may be cathodically reduced back to the neutral starting material. DFT calculations show that the dimer of 1+ achieves its stability through formation of a single long (almost 3.3 A) Re-Re bond made possible when the HOMO in 1 is rehybridized away from the metal in the one-electron oxidation process. The pure salts [1][B(C6F5)4]2 and [2][B(C6F5)4]2 were isolated by preparative anodic electrochemistry. The former may be used for storage of the very strong one-electron oxidant 1+, which was used to prepare a number of oxidation products as their [B(C6F5)4]- salts.

A Voltammetric Study of the Kolbe Synthesis with Perfluorinated Oxa Acids: Influence of the Structure of the Fluorocarbon Residue

The Kolbe synthesis with two perfluorinated oxa acids, perfluoro-3,7-dioxa-2-methyloctanoic and perfluorotetrahydro-α-furylacetic, was studied voltammetrically on platinum and glassy carbon anodes in water-acetonitrile and methanol-acetonitrile solutions. The influence exerted on the process by the acid concentration, degree of its neutralization, and solvent was studied. The solvent-anode system exerts a differentiating effect on the reactivity of perfluorinated acids under the conditions of the Kolbe synthesis.

Self-supported paired electrosynthesis of 2,5-dimethoxy-2,5-dihydrofuran using a thin layer flow cell without intentionally added supporting electrolyte

2,5-Dimethoxy-2,5-dihydrofuran was prepared by the oxidation of furan and by the reduction of methanol solvent using a thin layer flow cell geometry with anode and cathode directly facing each other and without intentionally added electrolyte. Controlling factors for this kind of self-supported paired electrosynthesis, such as the electrode material, the current density, and the flow rate were optimized. The maximum chemical yield of 98% of pure product without work-up could be obtained with a combination of a glassy carbon anode and a platinum cathode in a single pass of furan solution.

Anodic oxidation of mono- and disubstituted 1,4-dimethoxybenzenes.

The electrochemical oxidation of mono- and disubstituted 1,4-dimethoxybenzene derivatives with zero, one, and two benzylic CH(2)X groups (X = OAc, Cl, OH) (5a-c and 6a-c) has been carried out by using both constant-current and controlled-potential techniques in methanol and in the presence of different electrolytes and working electrodes. Constant-current electrolysis in KOH-methanol solutions yielded mostly the corresponding 1,4-quinone derivatives from 5a-c and 6b, whereas the disubstituted 1,4-dimethoxybenzenes 6a,c underwent side-chain oxidation to form 2,5-dimethoxyterephthalaldehydes. Upon alteration of the medium from the commonly used basic KOH-methanol to neutral LiClO(4)-methanol, a new spectrum of products was achieved in most cases, involving novel coupling products from monosubstituted substrates and quinone derivatives from disubstituted ones. Controlled-potential oxidation at the glassy carbon anodes and in a neutral LiClO(4)-methanol medium led to more complex mixtures of products, namely, polymers and new coupling products from monosubstituted substrates and quinones and side-chain oxidation (or substitution) products from the disubstituted ones. Three new coupling products were isolated and characterized by X-ray measurements.

Formation of Carbon Nitride by Anode-Discharge Electrolysis of Molten Salt

Anode-discharge electrolysis was conducted with a glassy carbon anode and a LiCl-KCl melt containing and/or under 1 atm of Ar. By applying a dc voltage of 500 V, a discharge was generated between the melt and the anode whose tip was positioned above the bath surface. When anode-discharge electrolysis was conducted with a glassy carbon anode and a melt, carbon nitride compounds were not obtained. When anode discharge electrolysis was conducted with a melt, the obtained powder contained nitrogen atoms bonded to carbon. From the results of X-ray diffraction, electron probe microanalysis, and X-ray photoelectron spectroscopy, it was suggested that the obtained powder was a carbon nitride compound embedded in a graphite matrix. © 2002 The Electrochemical Society. All rights reserved.