Sol-gel Derived Carbon Ceramic Electrode Research Articles

High electrocatalytic effect of Au–Pd alloy nanoparticles electrodeposited on microwave assisted sol–gel-derived carbon ceramic electrode for hydrogen evolution reaction

Various Au–Pd bimetallic nanoparticles were electrodeposited on microwave irradiated carbon ceramic electrodes (MWCCE). Au:Pd molar ratios of 75:25, 50:50 and 25:75 were electrodeposited on MWCCE and their electrocatalytic activities for hydrogen evolution reaction (HER) were evaluated. Among them, the alloy with Au:Pd molar ratio of 25:75 showed highest electrocatalytic activity for HER. The structure and nature of these alloys were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma, and cyclic voltammetry. Alloying degree of bimetallic nanoparticles and electrodeposition time were optimized. The electrocatalytic activity of bimetallic nanoparticles was also compared with individual non-alloyed Au and Pd catalysts and the results showed that alloy nanoparticles have higher electrocatalytic activity for hydrogen evolution. The Tafel slopes ranges are obtained from 136 mV dec−1 to 165 mV dec−1 for HER on bare and modified MWCCE and kinetic parameters show that the Volmer step must control the HER. The stability of the best electrode is determined by chronopotentiometric and it showed a good stability.

Electrochemical behavior of an indenedione derivative electrodeposited on a renewable sol–gel derived carbon ceramic electrode modified with multi-wall carbon nanotubes: Application for electrocatalytic determination of hydrazine

A novel modified carbon ceramic electrode (CCE) containing multi-wall carbon nanotubes (MWCNTs) was fabricated by a sol–gel technique. The prepared MWCNT-CCE was modified by the electrodeposition of an indenedione derivative. The indenedione modified MWCNT-CCE (IMWCNT-CCE) shows one pair of peaks with surface confined characteristics. According to the theoretical model of Laviron, estimations were made in different pHs of the surface charge transfer rate constant, k s, and the charge transfer coefficient, α, for electron transfer between the indenedione derivative and MWCNT-CCE. The modified electrode shows a highly catalytic activity toward hydrazine electrooxidation at a wide pH range (5–9). The kinetic parameters such as the electron transfer coefficient, α, the heterogeneous rate constant, k′, and the exchange current of hydrazine at the IMWCNT-CCE were calculated as 0.29 ± 0.01, 2.7(±0.3) × 10 −3 cm s −1 and 0.17 ± 0.03 μA, respectively. Also, the modified electrode shows an excellent analytical performance for voltammetric determination of hydrazine. Differential pulse voltammetry (DPV) exhibits two linear dynamic ranges, 0.6–8.0 μM and 8.0–100.0 μM, and a lower detection limit of 0.29 μM for hydrazine. Finally, the practical analytical utility is illustrated by differential pulse voltammetric determination of hydrazine in auxiliary cooling water at IMWCNT-CCE and the accuracy of the results is verified in comparison with those obtained from the standard ASTM method.

Sol–gel derived carbon ceramic electrode for the investigation of the electrochemical behavior and electrocatalytic activity of neodymium hexacyanoferrate

The electrochemical properties of an electroactive rare earth metal hexacyanoferrate, neodymium hexacyanoferrate (NdHCF) were studied by mechanically attaching NdHCF samples to the surface of carbon ceramic electrodes (CCEs) derived from sol–gel technique. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of 0.241 V (versus SCE) at a scan rate of 20 mV s −1 in 0.5 M KCl solution. The voltammetric characteristics of the NdHCF-modified CCEs in the presence of different alkali metal cations (Li +, Na +, K +, Rb + and Cs +) were investigated by voltammetry. The NdHCF-modified CCEs presented a good electrocatalytic activity towards the reduction of hydrogen peroxide (H 2O 2), and was used for amperometric detection of H 2O 2. In addition, the NdHCF-CCEs exhibited a distinct advantage of simple preparation, surface renewal, good stability and reproducibility.

Amperometric detection of insulin at renewable sol–gel derived carbon ceramic electrode modified with nickel powder and potassium octacyanomolybdate(IV)

A renewable three-dimensional chemically modified carbon ceramic electrode (CCE) containing nickel powder and K4[Mo(CN)8] was constructed by sol-gel technique. The electrochemical properties and stability of modified electrode was evaluated by cyclic voltammetry in pH range 4-10. The redox couple of [Mo(CN)8] (4-/3-) was shown both as a solute in electrolyte solution and as a component of a carbon based conducting composite electrode. The apparent electron transfer rate constant (ks) and transfer coefficient (alpha) were determined by cyclic voltammetry and they were about 17.1 and 0.57 s(-1), respectively. The catalytic activity of the modified CCE toward insulin oxidation was investigated at pH range of 3-8 by cyclic votammetry. The modified electrode showed excellent electrocatalytic activity toward insulin electroxidation at physiological pH value. The modified electrode was used for insulin detection chronoamperometrically at pH 7. Under optimized condition in amperometry method, the concentration calibration range, detection limit and sensitivity were 0.5-500 nM, 0.45 nM and 6140 nA/microM, respectively. Flow injection amperometric determination of insulin at pH 7.4, at this modified electrode yielded a calibration curve with the following characteristics, linear dynamic range 100-500 pM; sensitivity 8.1 nA/nM and detection limit 40 pM (based on S/N = 3). The inherent stability at wide pH range, high sensitivity, low detection limit, low cost and ease of preparation are of advantageous of this insulin sensor. This sensor indicates great promise for monitory insulin in chromatographic effluents.

Renewable Surface Sol-Gel Derived Carbon Ceramic Electrode Modified with [Ru(NH3)5Cl](PF6)2 Complex : Application to Amperometric Detection of Chlorate

A novel modified carbon ceramic electrode (CCE ) containing [Ru(NH3)5 Cl](PF6)2 complex was fabricated by sol-gel technique. The cyclic voltammograms of the modified electrodes show a well defined redox couple due to Ru(III)/Ru(II) system with surface confined characteristics. The stability of the modified CCE modified with ruthenium complex was checked over several days, obtaining reproducible results. Chlorate has been chosen as a model to elucidate the electrocatalytic ability of modified CCE. The modified electrode showed excellent electrocatalytic activity toward chlorate electroreduction in acidic medium. Chlorate was determined amperometrically at the surface of this modified electrode in pH 2 solution. Under the optimized conditions the calibration curve is linear in the concentration range 10 μM−5 mM chlorate. The detection limit and sensitivity are 1 μM and 0.43 nA/μM respectively. The advantages of the modified CCE is its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity and simplicity of preparation. This sensor can be used as an amperometric detector in flow systems. or chromatographic instruments.

Renewable Surface Sol-gel Derived Carbon Ceramic Electrode Modified with Copper Complex and Its Application as an Amperometric Sensor for Bromate Detection

A sol-gel technique was used for the preparation of a three dimensional carbon composite electrode modified with [Cu(bpy)2]Br2 complex. A reversible redox couple of Cu(II)/Cu(I) is observed at the electrode surface. The electrochemical behavior and stability of the modified electrode was characterized by cyclic voltammetry. The charge transfer coefficient (α) and charge transfer rate constant (Ks) for the modified electrode were determined by cyclic voltammetry, which were found to be 0.46 and 14.2 s−1, respectively. The modified electrode showed excellent catalytic activity toward bromate reduction at significantly reduced overpotentials and can be used successfully for amperometric detection of bromate. Under the optimized conditions, the calibration plots are linear in the concentration range 0.5 μM −200μM. Detection limit (signal to noise is 3) and sensitivity were found to be 0.1 μM and 20 nA / μM, respectively. These analytical parameters compare favorably with those obtained with modern analytical techniques. The modified carbon ceramic electrode doped with Cu-Complex shows a good reproducibility, a short response time (t<2 s), remarkable long term stability (>4 months) and especially good surface renewability by simple mechanical polishing (RSD for 6 successive polishing is 1.5%).

An amperometric hydrogen peroxide biosensor based on immobilizing horseradish peroxidase to a nano-Au monolayer supported by sol–gel derived carbon ceramic electrode

A novel strategy for fabricating horseradish peroxidase (HRP)-based H 2O 2 sensor has been developed by combining the merits of carbon sol–gel supporting matrix and nano-scaled particulate gold (nano-Au) mediator. The thiol functional group-derived carbon ceramic electrode (CCE) was first constructed using (3-mercaptopropyl) trimethoxy silane as sol–gel monomer. Then, the stable nano-Au monolayer was obtained through covalent linkage between nano-Au and thiol group on the surface of CCE. The experimental results showed that nano-Au monolayer formed not only could steadily immobilize HRP but also efficiently retain its bioactivity. Hydrogen peroxide was detected with the aid of hydroquinone mediator to transfer electrons between the electrode and HRP. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as the operating potential, mediator concentration and pH of background electrolyte were explored for optimum analytical performance of the enzyme electrode. The biosensor had a fast response of less than 8 s with linear range of 1.22×10 −5 to 1.10×10 −3mol l −1 and a detection limit of 6.1×10 −6mol l −1. The sensitivity of the sensor for H 2O 2 was 0.29 A l mol −1 cm −2. The activation energy for enzyme reaction was calculated to be 10.1 kJ mol −1. The enzyme electrode retained 75% of its initial activity after 5 weeks storage in phosphate buffer at pH 7.

Amperometric immunosensor for probing complement III (C 3) based on immobilizing C 3 antibody to a nano-Au monolayer supported by sol–gel-derived carbon ceramic electrode

An electrochemical immunosensor based on nano-size particulate gold (nano-Au) monolayer as sensing interface has been developed for probing complement III (C 3). The thiol functional group-derived carbon ceramic electrode (CCE) was firstly constructed using (3-mercaptopropyl) trimethoxy silane (MPTMOS) as sol–gel monomer. The stable nano-Au monolayer was obtained resulting from covalent combination between nano-Au and thiol group on the surface of CCE. The nano-Au monolayer formed was utilized as a sensing platform for the immobilization of C 3 antibody (anti-C 3) and subsequent immunoreaction. A competitive immunoassay format was adopted with horseradish peroxidase (HRP)–C 3 as a tracer, hydroquinone and hydrogen peroxide as the enzymatic substrates. The dynamic concentration range for C 3 is 0.08–5.6 μg ml −1. The feasibility of regenerating nano-Au monolayer for consecutive assays was demonstrated by a simple chemical treatment after each determination. The high stability of formed nano-Au monolayer, readily adsorptive immobilization of antibody on nano-Au monolayer, efficient activity retention of loading immunoreactants as well as the simple operation for the formation of nano-Au monolayer make proposed methodology an attractive alternative for the designing new-type immunosensors.

Sol-gel derived carbon ceramic electrode containing methylene blue-intercalated alpha-zirconium phosphate micro particles.

Methylene blue-intercalated alpha-zirconium phosphate (MBZrP) micro particles in deionized water were deposited onto the surface of graphite powder to prepare graphite powder-supported MBZrP, which was subsequently dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite. The composite was used as electrode material to fabricate a surface-renewable, rigid, leak-free carbon ceramic composite electrode, bulk-modified with methylene blue (MB). In the configuration, alpha-zirconium phosphate was employed as a solid host for MB, which acted as a catalyst. Graphite powder ensured conductivity by percolation, the silicate provided a rigid porous backbone and the methyl groups endowed hydrophobicity and thus limited the wetting section of the modified electrode. Peak currents of the MBZrP-modified electrode were surface-confined at low scan rates but diffusion-controlled at high scan rates. Square-wave voltammetric study revealed that MBZrP immobilized in carbon ceramic matrix presented a two-electron, three-proton redox process in acidic aqueous solution with pH ranged from 0.44 to 2.94. In addition, the chemically modified electrode showed an electrocatalytic activity toward nitrite reduction at +0.15 V ( vs. Ag/AgCl) in acidic aqueous solution (pH=0.44). The linear range and detection limit are 1x10(-6)-4x10(-3) mol x L(-1) and 1.5x10(-7) mol x L(-1), respectively.

Sol‐Gel Derived Carbon Ceramic Electrode Bulk‐Modified with Tris (1, 10‐phenanthroline‐5, 6‐dione) iron (II) Hexafluorophosphate and Its Use as an Amperometric Iodate Sensor

AbstractA surface‐renewable tris(1, 10‐phenanthroline‐5, 6‐dione) iron (D) hexafluorophosphate (FePD) modified carbon ceramic electrode was constructed by dispersing FePD and graphite powder in methyltrimethoxysilane (MTMOS) based gels. The FePD‐modified electrode presented pH‐dependent voltammetric behavior, and its peak currents were diffusion‐controlled in 0.1 mol/L Na2SO4 + H2SO4 solution (pH = 0.4). In the presence of iodate, dear electrocatalytic reduction waves were observed and thus the chemically modified electrode was used as an amperometric sensor for iodate in common salt. The linear range, sensitivity, detection limit and response time of the iodate sensor were 5 × 10−6–1 × 10−2 mol/L, 7.448 μA·L/ mmol, 1.2 × 10−6 mol/L and 5 s, respectively. A distinct advantage of this sensor is its good reproducibility of surface‐renewal by simple mechanical polishing.

Renewable-surface sol-gel derived carbon ceramic electrode fabricated by [Ru(bpy)(tpy)Cl]PF6 and its application as an amperometric sensor for sulfide and sulfur oxoanions.

A highly sensitive and fast responding sensor for the determination of thiosulfate, sulfite, sulfide and dithionite is described. It consists of a chemically modified carbon ceramic composite electrode (CCE) containing [Ru(bpy)(tpy)Cl]PF6 complex that was constructed by the sol-gel technique. A reversible redox couple of Ru(II)/Ru(III) was observed as a solute in acetonitrile solution and as a component of carbon based conducting composite electrode. Electrochemical behavior and stability of modified CCE were investigated by cyclic voltametry, the apparent electron transfer rate constant (kappa(S)) and transfer coefficient (a) were determined by cyclic voltametry which were about 28 s(-1) and 0.43 respectively. Electrocatalytic oxidation of S(2-), SO3(2-), S2O4(2-) and S2O3(2-) were effective at the modified electrode at significantly reduced overpotentials and in the pH range 1-11. Optimum pH values for amperometric detection of thiosulfate, dithionite, sulfide and sulfite are 7, 9, 2 and 2. Under the optimized conditions the calibration curves are linear in the concentration ranges 1-500, 3-80, 2-90 and 1-100 microM for S2O3(2-), SO3(2-), S2- and S2O4(2-) determination. The detection limit (signal to noise is 3) and sensitivity are 0.5 and 12, 2.8 and 6, 1.6 and 8, and 0.65 microM and 80 nA microM(-1) for thiosulfate, sulfite, sulfide and dithionite detection. The modified carbon ceramic electrode doped with Ru-complex shows good reproducibility, a short response time (t < 2 s), remarkable long term stability (> 6 month) and especially good surface renewability by simple mechanical polishing (RSD for eight successive polishing is 2%). The advantages of this sulfur compound amperometric detector based on ruthenium doped CCE are high sensitivity, inherent stability at a broader pH range, excellent catalytic activity, less expense and simplicity of preparation in comparison with recently published papers. This sensor can be used as a chromatographic detector for analysis of sulfur derivatives.

Sol-gel-derived carbon ceramic electrode containing 9,10-phenanthrenequinone, and its electrocatalytic activity toward iodate.

9,10-Phenanthrenequinone (PQ) supported on graphite powder by adsorption was dispersed in propyltrimethoxysilane-derived gels to yield a conductive composite which was used as electrode material to fabricate a PQ-modified carbon ceramic electrode. In this configuration, PQ acts as a catalyst, graphite powder guarantees conductivity by percolation, the silicate provides a rigid porous backbone, and the propyl groups endow hydrophobicity and thus limit the wetting region of the modified electrode. Square-wave voltammetry was exploited to investigate the pH-dependent electrochemical behavior of the composite electrode and an almost Nernstian response was obtained from pH 0.42 to 6.84. Because the chemically modified electrode can electrocatalyze the reduction of iodate in acidic aqueous solution (pH 2.45), it was used as an amperometric sensor for the determination of iodate in table salt. The advantages of the electrode are that it can be polished in the event of surface fouling, it is simple to prepare, has excellent chemical and mechanical stability, and the reproducibility of surface-renewal is good.