Platinum-modified polyaniline/polysulfone composite film electrodes and their electrocatalytic activity for methanol oxidation

The polyaniline/polysulfone (PAN/PSF) composite films were prepared by electropolymerization, and then platinum was deposited into this composite film to obtain the platinum-modified polyaniline/polysulfone(Pt/PAN/PSF) composite film electrodes. Their component, morphology and structure were characterized by FTIR spectra, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the composite film has a bi-layer structure with asymmetrical pores, and the platinum particles are homogeneously dispersed in the modified film electrodes. The cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied to investigate the electrochemical properties and the electrocatalytic activity of the modified film electrodes, which show a promotive action for methanol oxidation and the methanol oxidation under a diffusion-controlled process.     

氢氧化镍薄膜修饰玻碳电极的制备及其对L-赖氨酸氧化的电催化活性

采用恒电位沉积方法将氢氧化镍沉积到玻碳电极表面,得到稳定性高、催化活性好的氢氧化镍薄膜修饰玻碳电极;分析了影响薄膜形成过程的关键因素,确定了最佳薄膜制备方案;与此同时,将薄膜修饰玻碳电极用于生物样品L-赖氨酸的氧化测定,并探讨了其催化作用机理.结果表明,所制备的氢氧化镍薄膜修饰玻碳电极表面发生电化学反应[Ni(OH)2→NiOOH],从而促进电极表面的电子转移,实现对L-赖氨酸的电催化作用.当L-赖氨酸的浓度在1.0×10-4～4.0×10-7 mol/L范围内时,相应氧化峰电流与浓度呈线性关系,检出限达4.0×10-7 mol/L;据此可方便地制备稳定性好且灵敏度高的电流型传感器.     

Novel nano-zeolite modified carbon paste electrode for electrocatalytic oxidation of methanol

Abstract  

Methanol is used as a fuel in the direct methanol fuel cell. Direct oxidation of methanol encounters large overvoltages at most unmodified electrode surfaces. The development of new procedures for electrocatalytic oxidation of methanol to decrease this overvoltage is therefore very desirable. In this paper, we report a new zeolite-modified carbon paste electrode based on Ni-ZSM-5 for methanol electrooxidation. Nanocrystallites of ZSM-5 (Si/Al of 50) with average particle size of 58 nm were synthesized using clear solutions at low temperature (90 °C) under atmospheric pressure. Ni(II) ions were incorporated into the zeolite by immersion of the modified carbon paste electrode with synthesized zeolite in a 1.0 M nickel chloride solution. Cyclic voltammetry showed that by using nano-sized zeolite, the oxidation current increased compared with that of micron-sized zeolite crystallites.     

Nickel pentacyanonitrosylferrate film modified aluminum electrode for electrocatalytic oxidation of hydrazine

The electrocatalytic oxidation of hydrazine at the aluminum electrode, modified by electroless deposition of nickel pentacyanonitrosylferrate (NiPCNF) on the surface of the electrode has been studied by cyclic voltammetry, chronoamperometry and rotating disk electrode voltammetry and the kinetics of the catalytic reaction were investigated. The results were explained using the theory of electrocatalytic reactions at chemically modified electrodes. It was found that a one-electron charge-transfer process is rate limiting and that the average values of the rate constant for the catalytic reaction and the diffusion coefficient, evaluated by different approaches, are 5.2×10³ M^–1s^–1 and 8.5×10^–6 cm²s^–1, respectively. Further examinations of the modified electrodes show that the modifying layers (NiPCNF) on the aluminum substrate have reproducible behavior and a high level of stability, after exposing them in air and hydrazine solutions for a long time. Electronic Publication     

Electrocatalytic oxidation of methanol on Ni modified polyaniline electrode in alkaline medium

Electrolytically deposited Ni on polyaniline film covered carbon paste electrode (Ni/PANI/CPE) was used as anode for the electrooxidation of methanol in alkaline medium. The electrochemical behavior and electrocatalytic activity of the electrode were studied using cyclic voltammetry, impedance spectroscopy, chronomethods, and polarization studies. The morphology and composition of the modified film were obtained using scanning electron microscope and energy dispersive X-ray analysis techniques. The electrooxidation of methanol in NaOH was found to be more efficient on Ni/PANI/CPE than on bare Ni, electrodeposited Ni on Pt, Ni on glassy carbon, and Ni on CPE substrates. Partial chemical displacement of dispersed Ni on PANI with Pt or Pd further improved its performance towards methanol oxidation.     

Electrocatalytic oxidation and flow-injection determination of ascorbic acid at a graphite electrode modified with a polyaniline film containing electrodeposited palladium

A method for forming a composite film on the surface of a graphite electrode is proposed. Conditions for detecting the maximum catalytic current under batch and flow conditions are determined. A procedure for the electrocatalytic determination of ascorbic acid at the graphite electrode modified with a polyaniline film containing palladium particles is proposed. The catalytic effect of this electrode manifests itself by a ～300-mV decrease in the peak potential of ascorbic acid oxidation and by a multiple increase in the peak current of ascorbic acid oxidation as compared to the unmodified electrode. The linear dependence of the electrocatalytic response of the composite electrode on the concentration of ascorbic acid is observed down to 1 × 10^?8 M and 2.5 nmol of ascorbic acid under batch and flow-injection analysis conditions, respectively.     

Multi-walled carbon nanotubes modified glass carbon electrode and its electrocatalytic activity towards oxidation of paracetamol

Multi-walled carbon nanotubes (MWNTs) modified glassy carbon electrode (GCE) was simply and conveniently fabricated. The electrochemical properties of paracetamol (PCT) at the prepared modified electrode were investigated by cyclic voltammetry (CV). Based on this, an ultrasensitive and rapid electrochemical method was developed for the determination of PCT. The result indicated that the oxidation of PCT was greatly improved at the MWNTs-modified GC (MWNTs/GC) electrode as compared with the bare GC electrode, with relatively high sensitivity, stability and life time. Good linear relationship between the oxidation peak current and the PCT concentration in the range of 1 × 10⁻⁷ to 1 × 10⁻³ M (r = 0.996) was obtained in phosphate buffer solution (PBS) with pH 6.5, the detection limit was 2 × 10⁻⁸ M (S/N = 3) by use of modified electrode. The proposed method was successfully applied to the PCT determination in tablets.     

Platinum-coated gold nanoporous film surface: electrodeposition and enhanced electrocatalytic activity for methanol oxidation

This report describes the preparation of Pt-nanoparticle-coated gold-nanoporous film (PGNF) on a gold substrate via a simple "green" approach. The gold electrode that has been anodized under a high potential of 5 V is reduced by freshly prepared ascorbic acid (AA) solution to obtain gold nanoporous film electrode. Then the Pt nanoparticle is grown on the electrode by cyclic voltammetry (CV). The resulting PGNF electrode has highly ordered arrangement and large surface area, as verified by scanning electron microscopy (SEM) and CV, suggesting that the nanoporous gold film electrode provides a good matrix for obtaining PGNF with high surface area. Furthermore, the as-prepared PGNF electrode exhibited high electrocatalytic activity toward methanol oxidation in a 0.5 M H 2SO 4 solution containing 1.5 M methanol. The present novel strategy is expected to reduce the cost of the Pt catalyst remarkably.     

Oscillatory electrocatalytic oxidation of methanol on an Ni(OH)2 film electrode

A film of Ni(OH)₂ deposited cathodically on a roughened nickel substrate consists of even nanoparticles, which were characterized by atomic-force microscopy (AFM). The mechanism of potential oscillations in the electrocatalytic oxidation of methanol on this film electrode in alkaline medium was studied in situ by means of Raman spectroscopy in combination with electrochemical measurements. The redox change of the nickel hydroxide film, the concentration distribution of methanol in the diffusion layer, and the oxidation products of methanol were characterized in situ by time-resolved, spatial-resolved, and potential-dependent Raman spectroscopy, respectively. Electrochemical reactions, i.e. methanol oxidation and periodic oxygen evolution, coupling with alternately predominant diffusion and convection mass transfer of methanol, account for the potential oscillations that occur during oxidation of methanol above its limiting diffusion current. This mechanism is totally different from that of methanol oxidation on platinum electrodes, for which surface steps, i.e. formation and removal of CO_ad, are essential.This work is dedicated to Professor Gyorgy Horanyi on the occasion of his 70th birthday in recognition of his numerous contributions to field of electrochemical oscillations and electrocatalysis at Ni-hydroxide electrodes.     

Pt-Ru/GC电极对甲醇电催化氧化的研究

利用循环伏安法制备了Pt-Ru/GC电极并用于对甲醇的电催化氧化研究,考察了Pt、Ru原子比、沉积电位下限和沉积量对电极催化性能的影响,研究了电极催化性能的稳定性。结果表明Ru的加入对电极催化性能具有明显的改善作用,对甲醇的氧化电位范围明显变宽,氧化电流明显增大,电极的稳定性明显高于Pt/GC电极。在Pt、Ru原子比为1:1、沉积电位下限为-0.2V、沉积量为40r的条件下,Pt-Ru/GC电极对甲醇电催化氧化的性能最好。     

Green and facile synthesis of Pt/{PW12-GN} composite film and its electrocatalytic activity for methanol oxidation

In this paper, H₃PW₁₂O₄₀ (PW₁₂)-functionalized graphene nanosheets (PW₁₂-GNs) were prepared using a green and facile method via a UV-irradiated photoreduction process, in which PW₁₂ was directly deposited on the GNs as a reductant and also as an anionic stabilizer. The as-prepared water-dispersive PW₁₂-GN composite is used as matrices for electrodeposition of the interesting orchidlike Pt nanoclusters in situ. The PW₁₂-GN composite was characterized by transmission electron microscopy (TEM) and cyclic voltammetry (CV). It was shown that the electrochemical properties of PW₁₂ were maintained in PW₁₂-GNs. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) confirmed that Pt had been deposited on the PW₁₂-GN composite surface. Field emission scanning electron microscopy (FE-SEM) showed that the interesting orchidlike Pt nanoparticles were uniformly immobilized on the surface of the {PW₁₂-GN} composite film. Cyclic voltammetry and chronoamperometric curves were used to study the electrocatalytic activity of Pt/{PW₁₂-GN} regarding methanol oxidation in 0.5 M H₂SO₄. It is worthy of note that the Pt/{PW₁₂-GN} composite film-modified electrode presents a high catalytic activity (j?=?353 mA mg^?1) and better tolerance of CO towards methanol electrooxidation.     

Formate,an active intermediate for direct oxidation of methanol on pt electrode

The electro-oxidation of methanol on a Pt thin film electrode in acidic solution has been investigated by in situ surface-enhanced IR absorption spectroscopy. A new IR peak is observed at around 1320 cm-1 when the electrode potential is more positive than 0.5 V, where the bulk oxidation of MeOH occurs. This peak has been assigned to the symmetric stretching of formate species adsorbed on the Pt electrode surface. It is the first observation of formate adsorption during the electro-oxidation of methanol on a Pt surface. A near proportional relationship between the intensity of the IR band of the formate species and MeOH electro-oxidation current is observed. A new reaction scheme via non-CO pathway with formate as the active intermediate is proposed for the methanol electro-oxidation process.     

Characterization of carbon-supported AuPt nanoparticles for electrocatalytic methanol oxidation reaction

In view of the recent finding that the bimetallic AuPt nanoparticles prepared by molecular-capping-based colloidal synthesis and subsequent assembly on carbon black support and thermal activation treatment exhibit alloy properties, which is in sharp contrast to the bimetallic miscibility gap known for the bulk counterparts in a wide composition range, there is a clear need to assess the electrocatalytic properties of the catalysts prepared with different bimetallic composition and different thermal treatment temperatures. This paper reports recent results of such an investigation of the electrocatalytic methanol oxidation reaction (MOR) activities of the carbon-supported AuPt nanoparticle catalysts with different bimetallic composition and thermal treatment temperatures. Au(m)Pt(100)(-)(m) nanoparticles of 2-3 nm core sizes with different atomic compositions ranging from 10% to 90% Au (m = 10 approximately 90) have been synthesized by controlling the feeding of the metal precursors used in the synthesis. The electrocatalytic MOR activities of the carbon-supported AuPt bimetallic catalysts were characterized in alkaline electrolytes. The catalysts with 65% to 85% Au and treated at 500 degrees C were found to exhibit maximum electrocatalytic activities in the alkaline electrolytes. The findings, together with a comparison with some well-documented catalysts as well as recent experimental and theoretical modeling results, have revealed important insights into the participation of CO(ad) and OH(ad) on Au sites in the catalytic reaction of Pt in the AuPt alloys with approximately 75% Au. The insights are useful for understanding the correlation of the bifunctional electrocatalytic activity of the bimetallic nanoparticle catalysts with the bimetallic composition and the thermal treatment temperatures.     

A new polyphenol modified electrode containing an anchored ruthenium complex and its use in electrocatalytic oxidation of organic substrates

This work describes the preparation of a new modified electrode containing a ruthenium complex (cis-aquadimethylbipyridyltriphenylphosphineruthenium II), bonded to a stable polyphenol film. This modified electrode promotes the fast electrocatalytic oxidation of safrol (5-allyl-benzo[1,3]dioxole) and isosafrol (5-propenyl-benzo[1,3]dioxole), giving two interesting products benzo[1,3]dioxole-5-carbaldehyde (piperonal) and 3-benzo[1,3]dioxol-5-yl-propenal respectively, with good yields. The electrode preparation can be carried out at a potential range which does not interfere on the anchored electroactive ruthenium complex, but it allows for the phenol oxidation to occur and therefore polymerize forming the polyphenol film. The catalytic character of this modified electrode is showed by its high turnover numbers. The procedure to isolate the products is very simple.     

Nickel modified ionic liquid/carbon paste electrode for highly efficient electrocatalytic oxidation of methanol in alkaline medium

In this study, the electrocatalytic oxidation of methanol at nickel modified ionic liquid/carbon paste electrode (Ni/IL/CPE) in alkaline medium is presented. The ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, is incorporated into the electrode as a binder. Electrochemical impedance spectroscopy is employed to evaluate the electron transfer rate of this electrode. Ni(II) ions are incorporated into the electrode by immersion of this electrode in 1.0?M nickel sulfate solution. Cyclic voltammetry and chronoamperometry techniques are used for the electrochemical study of this modified electrode in the absence and the presence of methanol. The effect of methanol concentration on the anodic peak current shows an increase in the anodic peak current up to 1.25?M. Current density of Ni/IL/CPE for methanol oxidation in alkaline media is investigated by comparison with some of the previously reported electrodes. Results show that this electrode exhibits a high efficient electrocatalytic activity toward the oxidation of methanol with the current density of 17.6?mA?cm^?2. The rate constant for chemical reaction between methanol and redox sites of electrode is calculated. This new proposed electrode is simple and efficient enough, and it can be widely used as anode in direct methanol fuel cell.     

Electrochemistry and electrocatalytic activity of catechin film on a glassy carbon electrode toward the oxidation of hydrazine

A very stable electroactive film of catechin was electrochemically deposited on the surface of activated glassy carbon electrode. The electrochemical behavior of catechin modified glassy carbon electrode (CMGCE) was extensively studied using cyclic voltammetry. The properties of the electrodeposited films, during preparation under different conditions, and the stability of the deposited film were examined. The charge transfer coefficient (α) and charge transfer rate constant (k _s) for catechin deposited film were calculated. It was found that the modified electrode exhibited excellent electrocatalytic activity toward hydrazine oxidation and it also showed a very large decrease in the overpotential for the oxidation of hydrazine. The CMGCE was employed to study electrocatalytic oxidation of hydrazine using cyclic voltammetry, rotating disk voltammetry, chronoamperometry, amperometry and square-wave voltammetry as diagnostic techniques. The catalytic rate constant of the modified electrode for the oxidation of hydrazine was determined by cyclic voltammetry, chronoamperometry and rotating disk voltammetry and was found to be around 10⁻³ cm s⁻¹ . In the used different voltammetric methods, the plot of the electrocatalytic current versus hydrazine concentration is constituted of two linear segments with different ranges of hydrazine concentration. Furthermore, amperometry in stirred solution exhibits a detection limit of 0.165 μM and the precision of 4.7% for replicate measurements of 40.0 μM solution of hydrazine.     

咪唑四氟硼酸盐离子液体中磷钼酸掺杂聚吡咯薄膜修饰电极的制备及其电催化活性

以1-丁基-3-甲基咪唑四氟硼酸盐(BMIMBF4)离子液体作为介质,利用电化学方法在铂电极表面制备了磷钼酸掺杂聚吡咯薄膜;采用扫描电子显微镜观察了所制备的薄膜的形貌,利用热重分析评价了其热稳定性,利用循环伏安法测定了其电化学活性和对甲醇的电催化氧化活性.结果表明,与传统的硫酸溶液相比,以BMI-MBF4离子液体作为反应介质制备的修饰电极的表面形貌更均匀,电化学活性和对甲醇的电催化氧化活性更强.     

Voltammetry determination of dopamine by the electrocatalytic response of an electrode modified by a polyaniline film with an inclusion of copper(II) tetrasulfophthalocyanine

A polyaniline composite film with an inclusion of copper(II) tetrasulfophthalocyanine, applied on a glassy-carbon electrode (GC) has demonstrated a mediatory activity in the oxidation of dopamine in acidic and neutral media. The conditions for the formation of a polymer film on the surface of a glassy-carbon electrode for registering the maximum electrocatalytic effect in the oxidation of dopamine are found. A method of voltammetric and amperometric detection of dopamine on the composite film electrode under static and flow conditions is proposed. The use of a polyaniline composite with an inclusion of copper(II) tetrasulfophthalocyanine, coated with a Nafion film, made possible the reduction of the detection limit for dopamine to 1 × 10^?8 M under static conditions and to 5.0 nmol under the conditions of flow-injection analysis.