Carbon Electrode In Alkaline Solution Research Articles

Tuning Selectivity and Sensitivity of Mixed‐polymeric Tetraruthenated Metalloporphyrins Modified Electrodes as Voltammetric Sensors of Chloramphenicol

AbstractMixed Ni−Co tetraruthenated porphyrin films were successfully electropolymerized on glassy carbon electrodes in alkaline solutions (pH=13) of NiTRP and CoTRP, giving excellent electrocatalytic responses for determination of the antibiotic drug chloramphenicol. Electrodes with four different compositions were obtained by varying the ratio of NiTRP and CoTRP in the deposition solution. For the characterization of these materials, SEM, ICP‐MS, EIS and CV were explored. The porphyrin modified glassy carbon electrodes presented two oxidation peaks for chloramphenicol (except for Ni‐25). The potential shifted to lower values as the percentage of CoTRP increased decreasing its oxidation potential in more than 200 mV for Ni‐50 as compared to Ni‐100. Interestingly, the materials with cobalt content larger than 50 % did not show the typical catalytic response of the NiIIIOOH species, but rather showed an increase in current at potentials larger than 0.4 V, demonstrating the key role played by nickel in this type of materials. The composition of polymeric mixed porphyrin materials influenced the oxidation current response of both redox waves, resulting in different sensitivities on the calibration curves.

The impedance response of different mechanisms for LiCoO2/acetylene carbon electrodes in alkaline solutions under polarization conditions

The kinetics of LiCoO2 electrodes with different carbon ratios in alkaline aqueous solutions was studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The composition of the electrode influences the mechanism controlling the interface. The redox reactions identified by CV indicated the potential regions where the charge transfer process is the dominant mechanism. EIS in (Li2SO4+LiOH) alkaline solutions characterized different interfacial mechanisms when potential bias was applied to electrodes formed with different acetylene carbon (AC)/LiCoO2 ratios. The different carbon/active ratios revealed different interfacial characteristics due to the cylindrical porous distribution of the composite electrode. DC and AC techniques were performed to characterize the interfacial mechanisms influenced by composite ratio, particle geometry and distribution under bias conditions. Transmission line modeling (TLM) was used to characterize the impedance signal resulting from the physical parameters influencing the mechanisms occurring at the porous composite layer/electrolyte interface. Interfacial mechanisms associated with TLM elements helped to quantitatively characterize the functionality of the different LiCoO2/AC ratios present in the electrode compositions. The proposed TL model was validated with the experimental data and high surface characterization, resulting in good agreement.

Oxygen reduction on molybdenum carbide derived micromesoporous carbon electrode in alkaline solution

Micromesoporous carbide derived carbon powder, synthesized from molybdenum carbide (Mo2C) at 750°C using high-temperature chlorination method, and was used as a catalyst for oxygen electroreduction. Cyclic voltammetry and rotating disc electrode data show that very high cathodic current density of −70 A m−2 has been achieved for 0.1M KOH aqueous solution saturated with O2. There are two clearly separable linear regions in the Tafel plot for C(Mo2C) electrode, indicating that the oxygen reduction reaction (ORR) mechanism depends on the electrode potential applied. Very high half-wave potentials have been measured, demonstrating that C(Mo2C) is a very active catalyst for ORR.

Electrocatalytic oxygen reduction on silver nanoparticle/multi-walled carbon nanotube modified glassy carbon electrodes in alkaline solution

The electrochemical reduction of oxygen was studied on Ag nanoparticle/multi-walled carbon nanotube (AgNP/MWCNT) nanocomposites in alkaline solution employing the rotating disk electrode (RDE) method. The composite material was prepared by sputter deposition of Ag catalyst on the surface of MWCNTs. The surface morphology of the AgNP/MWCNT composites was examined by scanning electron microscopy (SEM). The SEM images show that there is a wide size distribution of Ag particles on MWCNTs. The RDE results reveal a high electrocatalytic activity of the AgNP/MWCNT nanocomposites towards the oxygen reduction reaction (ORR). On these catalysts the ORR proceeds by a four-electron pathway. The AgNP/MWCNT composite is a good catalyst for peroxide reduction. The results obtained are important for the development of Ag-based catalysts for alkaline membrane fuel cells.

Electrocatalytic reduction of oxygen on bimetallic copper–gold nanoparticles–multiwalled carbon nanotube modified glassy carbon electrode in alkaline solution

Multiwalled carbon nanotubes (MWCNTs) were functionalized with acid treatment and thereafter gold–copper nanoparticles were electrodeposited on the MWCNTs by applying several repetitive scans, thus forming a Cu–Au–MWCNT/GCE interface. The electrochemical reduction of oxygen was studied on this modified electrode in 0.1 M NaOH solution. The electrocatalytic activity on the Cu–Au–MWCNT/GCE showed a tendency towards the O 2 reduction. The peak potential of O 2 reduction on the Cu–Au–MWCNT/GCE shifted ca. 70 mV higher positive potentials as compared to that of a polished glassy carbon electrode. A significant current enhancement was obtained on the Cu–Au–MWCNT/GCE compared to that of bare GCE, MWCNT/GCE, Cu–MWCNT/GCE and Au–MWCNT/GCE. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed in order to investigate the surface morphology and elemental composition of the modified electrode, respectively.

Electrocatalytic oxidation of some amino acids on a cobalt hydroxide nanoparticles modified glassy carbon electrode

In this study we investigated the electrocatalytic oxidation of cysteine, cystine, N-acetyl cysteine, and methionine on cobalt hydroxide nanoparticles modified glassy carbon electrode in alkaline solution. Different electrochemical techniques such as cyclic voltammetry, chronoamperometry and steady-state polarization were used to track the oxidation process and its kinetics. From voltammetric studies we concluded that in the presence of amino acids the anodic peak current of Co(IV) species increased, followed by a decrease in the corresponding cathodic current peak. This indicates that amino acids were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron’s equation, the values of α s and k s for the immobilized redox species were determined as α s , a = 0.63, α s,c = 0.38 and k s = 0.28 s −1, respectively. The catalytic rate constants, the electron transfer coefficients and the diffusion coefficients involved in the electrocatalytic oxidation of amino acids were determined.

Oxygen reduction on carbon nanomaterial-modified glassy carbon electrodes in alkaline solution

Electroreduction of oxygen in alkaline solution on glassy carbon (GC) electrodes modified with different carbon nanomaterials has been studied. Electrochemical experiments were carried out in 0.1 M KOH employing the rotating disk electrode and rotating ring-disk electrode methods. The GC disk electrodes were modified with carbon nanomaterials using polytetrafluoroethylene as a binder. Four different carbon nanomaterials were used: multiwalled carbon nanotubes, carbon black powder, and two carbide-derived carbons (CDC). For the first time, the electrocatalytic behavior of CDC materials toward oxygen reduction is explored. Electrochemical characterization of the materials showed that all the carbon nanomaterial-modified GC electrodes are highly active for the reduction of oxygen in alkaline solutions.

Nano-structured Ni(II)–curcumin modified glassy carbon electrode for electrocatalytic oxidation of fructose

A nano-structured Ni(II)–curcumin (curcumin: 1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) film is electrodeposited on a glassy carbon electrode in alkaline solution. The morphology of polyNi(II)–curcumin (NC) was investigated by scanning electron microscopy (SEM). The SEM results show NC has a nano-globular structure in the range 20–50 nm. Using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) showed that the nano-structure NC film acts as an efficient material for the electrocatalytic oxidation of fructose. According to the voltammetric studies, the increase in the anodic peak current and subsequent decrease in the corresponding cathodic current, fructose was oxidized on the electrode surface via an electrocatalytic mechanism. The EIS results show that the charge-transfer resistance has as a function of fructose concentration, time interval and applied potential. The increase in the fructose concentration and time interval in fructose solution results in enhanced charge transfer resistance in Nyquist plots. The EIS results indicate that fructose electrooxidation at various potentials shows different impedance behaviors. At lower potentials, a semicircle is observed in the first quadrant of impedance plot. With further increase of the potential, a transition of the semicircle from the first to the second quadrant occurs. Also, the results obtained show that the rate of fructose electrooxidation depends on concentration of OH −. Electron transfer coefficient, diffusion coefficient and rate constant of the electrocatalytic oxidation reaction are obtained. The modified electrode was used as a sensor for determination of fructose with a good dynamic range and a low detection limit.

Electrocatalytic glucose oxidation at bimetallic gold–copper nanoparticle-modified carbon electrodes in alkaline solution

To achieve both oxidation reactions at a more negative potential and better reactions in electrocatalytic glucose oxidation, AuCu alloy nanoparticles were synthesized and their activities for glucose oxidation in alkaline solution were investigated by voltammetric and controlled-potential electrolysis studies. Decanethiol-encapsulated (DT-) Au nano, DT-Au 97Cu 3 (m: atomic%), and DT-Cu nano nanoparticles were synthesized, and their core sizes were determined to be 2 (±1), 2 (±1), and 4 (±2) nm, respectively. To remove the DT monolayer from the DT-Au nano, DT-Au 97Cu 3 and DT-Cu nano nanoparticles, nanoparticle-modified plastic-formed carbon plate (PFC) electrodes were heated at 300 °C for 2 h. Elimination of the DT was confirmed by FT-IR and XPS measurements. The surface metal atomic content ratios of DT-Au 97Cu 3 eventually changed to Au 77Cu 23, after the heat-treatment. The voltammetric behavior of electrocatalytic glucose oxidation at the Au 77 Cu 23 nanoparticle-modified electrodes in alkaline solution was similar to the Au nano nanoparticle-modified electrodes, in which the potential was more negative than a Cu nano nanoparticle-modified electrode and bulk-like Cu electrodes. Upon controlled-potential electrolysis, Au 77 Cu 23 nanoparticle-modified electrodes gave gluconolactone and formate as main products, which indicated that electrocatalytic oxidation, was promoted in comparison with the Au nano nanoparticle-modified electrodes. It is concluded that Au 77Cu 23 nanoparticles have both advanced properties of Au nano and Cu nano nanoparticles for glucose oxidation.

Electrocatalytic oxidation of aspirin and acetaminophen on a cobalt hydroxide nanoparticles modified glassy carbon electrode

The electrocatalytic oxidation of aspirin and acetaminophen on nanoparticles of cobalt hydroxide electrodeposited on the surface of a glassy carbon electrode in alkaline solution was investigated. The process of oxidation and the kinetics have been investigated using cyclic voltammetry, chronoamperometry, and steady-state polarization measurements. Voltammetric studies have indicated that in the presence of drugs, the anodic peak current of low valence cobalt species increases, followed by a decrease in the corresponding cathodic current. This indicates that drugs are oxidized on the redox mediator which is immobilized on the electrode surface via an electrocatalytic mechanism. With the use of Laviron’s equation, the values of anodic and cathodic electron-transfer coefficients and charge-transfer rate constant for the immobilized redox species were determined as α s,a = 0.72, α s,c = 0.30, and k s = 0.22 s−1. The rate constant, the electron transfer coefficient, and the diffusion coefficient involved in the electrocatalytic oxidation of drugs were reported. It was shown that by using the modified electrode, aspirin and acetaminophen can be determined by amperometric technique with detection limits of 1.88 × 10−6 and 1.83 × 10−6 M, respectively. By analyzing the content of acetaminophen and aspirin in bulk forms using chronoamperometric and amperometric techniques, the analytical utility of the modified electrode was achieved. The method was also proven to be valid for analyzing these drugs in urine samples.

Biofuel Cells Using Au Nano-particle Immobilized Carbon Electrodes in Alkaline Solutions

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Investigation of oxygen reduction on activated carbon electrodes in alkaline solution

Oxygen reduction has been studied on gas diffusion electrodes made from various kinds of activated carbon materials. The potentiodynamic method was used to study the electrochemical behavior of the reduction reaction, while nitrogen gas adsorption and powder X-ray diffraction were used to determine the pore size distribution and the crystal structure of the carbon material, respectively. The relationship between the catalytic activity of activated carbon and the surface content of edge orientation was discussed. The specific catalytic activity of activated carbon is determined by the percentage of the edge orientation on the surface. The higher the content of the edge plane, the lower the oxygen reduction overpotential. The reduction overpotential is also related to the effective surface area, which determines the local current density.

Electrocatalytic oxidation of some amino acids on a nickel–curcumin complex modified glassy carbon electrode

This study investigated the electrocatalytic oxidation of alanine, l-arginine, l-phenylalanine, l-lysine and glycine on poly-Ni(II)–curcumin film (curcumin: 1,7-bis [4-hydroxy-3-methoxy phenyl]-1,6-heptadiene-3,5-dione) electrodeposited on a glassy carbon electrode in alkaline solution. The process of oxidation and its kinetics were established by using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques. Voltammetric studies indicated that in the presence of amino acids the anodic peak current of low valence nickel species increased, followed by a decrease in the corresponding cathodic current. This indicates that amino acids were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron's equation, the values of α and k s for the immobilized redox species were determined as 0.43 ± 0.03 and 2.47 ± 0.02 × 10 6 s −1, respectively. The rate constant, the electron transfer coefficient and the diffusion coefficients involved in the electrocatalytic oxidation of amino acids were determined.

Glucose-Air Biofuel Cells Prepared by Using Ag Ad-layer Modified Au and Au Nano-particle Immobilized Carbon Electrodes in Alkaline Solutions

not Available.

Oxygen electroreduction on chemically modified glassy carbon electrodes in alkaline solution

Abstract The electrochemical reduction of oxygen on glassy carbon (GC) electrodes modified with aryl groups has been studied using the rotating disk electrode (RDE) technique. The GC electrodes were grafted by electrochemical reduction of diazonium salts. The diazonium derivatives of benzene, naphthalene and anthracene were used in surface modification. The blocking behaviour of aryl layers towards oxygen reduction was investigated. An unexpected order of blocking efficiency of the aryl moieties was observed for O2 reduction in 0.1 M KOH. The phenyl-modified GC electrode was less active than those electrografted with naphthalene and anthracene. Comparative measurements were carried out in 1 mM K3Fe(CN)6. A much larger extent of blocking was evident for the Fe ( CN ) 6 3 - / 4 - couple. This effect was explained by a significant difference in size between the Fe ( CN ) 6 3 - / 4 - ions and O2 molecule. A mixed film of anthraquinone (AQ) and phenyl groups was formed by diazonium reduction and its relevance in the kinetics investigations was discussed. The kinetic parameters of oxygen reduction were determined using a surface redox catalytic cycle model for quinone-modified electrodes.

Electrochemical reduction of oxygen on anodically pre-treated and chemically grafted glassy carbon electrodes in alkaline solutions

The electrochemical reduction of oxygen on anodically pre-treated glassy carbon (GC) and on oxidised GC electrodes grafted with anthraquinone has been investigated using the rotating ring-disk electrode (RRDE) technique. Surface oxidation increases the electrocatalytic activity of GC for oxygen reduction to hydrogen peroxide. However, these electrodes catalyse the further reduction of HO 2 − at potentials more negative than approximately −0.9 V vs. SCE. The O 2 reduction behaviour is considerably altered when oxidised GC electrodes are grafted with anthraquinone.

Influence of anion and pH on the electrochemical behaviour of polypyrrole synthesised in alkaline media

The electrochemical behaviour of conducting polypyrrole films electrosynthesised on vitreous carbon electrodes in alkaline solutions has been investigated by means of cyclic voltammetry and open circuit potentiometric measurements. The shape and evolution of the voltammograms during cycling depend strongly on the kind of anion and solution pH used. From these results, anion and cation participation in the redox process of the polymer has been analysed. The transport of anions like NO 3 − or Cl − is dominant, while the transport of OH − is the most important contribution when the polymer is cycled in the presence of anions that cannot be incorporated into the polymer matrix. The incorporation of Na + also takes place and its contribution is more significant as deposition charge increases. The characteristics of the films are compared with those obtained in acid media. The polymerisation efficiency is similar in both cases. Films electrodeposited in alkaline solution can be doped and undoped in acid solution without loosing its redox behaviour.

Electrochemical reduction of oxygen on anthraquinone-modified glassy carbon electrodes in alkaline solution

The electrochemical reduction of oxygen on glassy carbon (GC) electrodes grafted with anthraquinone (AQ) has been studied using the rotating ring–disk electrode technique. Grafting was achieved by the electrochemical reduction of the corresponding diazonium salt and the effect of AQ surface concentration on the kinetics of oxygen reduction has been investigated. The two-electron reduction of oxygen to hydrogen peroxide was observed for all the quinone-modified electrodes studied and the catalytic activity of the electrodes for O 2 reduction was dependent on the AQ surface concentration. The kinetic parameters of oxygen reduction on GC/AQ electrodes in 0.1 M KOH were determined as a function of AQ surface concentration considering a surface redox catalytic cycle model for quinone-modified electrodes. The rate constant of the chemical reaction between the semiquinone radical anion of AQ and molecular oxygen has been determined.

Mechanism of hydrogen peroxide oxidation reaction at a glassy carbon electrode in alkaline solution

The voltammetric behavior of hydrogen peroxide at a glassy carbon electrode in alkaline solution was studied. An anodic prewave, preceding the well-known transport controlled oxidation reaction of hydrogen peroxide, was observed. The voltammetric current in this wave is independent of the rotation speed of the glassy carbon disc electrode, even in what looks like a limiting current plateau, denoted by a pseudo limiting current. This current is dependent strongly on pH and temperature, does not vary linearly with hydrogen peroxide concentration and the reaction orders, with respect to hydrogen peroxide and hydroxyl ions (pH), are dependent on the hydrogen peroxide concentration. A mechanism that can explain these experimental results has been proposed. It consists of two submechanisms, occurring simultaneously at the electrode surface, which are in competition with each other. Their relative predominance is controlled by the hydrogen peroxide concentration, which can explain the varying reaction orders with respect to hydroxyl ions and hydrogen peroxide. The current equation resulting from the proposed mechanism shows the possibility of using the studied electrode reaction for the amperometric determination of hydrogen peroxide up to high concentrations.

Particle size effects for oxygen reduction on dispersed silver + carbon electrodes in alkaline solution

Ag + C electrocatalysts with different Ag particle-size distributions were prepared by functional ion preadsorption method. The effects of the preadsorption of different halogen ions on carbon on Ag particle size and crystal structure were studied by transmission electron microscopy and a selected area diffraction method. The adsorption characteristics of Ag + on activated carbon were measured by an argentimetry method. The catalytic behaviour of Ag + C catalysts with different Ag particle size distributions for oxygen reduction in KOH solution was investigated using a soft-embedded microelectrode and soft-embedded rotating disc electrode with a platinum ring electrode. The results showed that oxygen reduction was a structure-sensitive reaction on silver particles. Decreased Ag particle size has a complicated effect on the four-electron reduction, but a favourable effect on two-electron reduction.