Carbon-supported Pd–Ir catalyst as anodic catalyst in direct formic acid fuel cell

It was reported for the first time that the electrocatalytic activity of the Carbon-supported Pd-Ir (Pd-Ir/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of formic acid. The potential of the anodic peak of formic acid at the Pd-Ir/C catalyst electrode with the atomic ratio of Pd and Ir = 5:1 is 50 mV more negative than that and the peak current density is 13% higher than that at the Pd/C catalyst electrode.

Application of Ru(bpy)(3)(2+) in control and formation of gold surface nanostructure through oxidation-reduction cycling

It was studied that the nanostructure formed on a gold surface via a simple oxidation-reduction cycles (ORC) in 0.1 M KCl containing Ru(bpy)(3)(2+) with different concentrations. Atomic force microscopy (AFM) and energy-dispersed spectroscopy (EDS) were used to characterize the nanostructure formed on the gold surface. Sweep-step voltammetry and corresponding electroluminescence (ECL) response, in situ electrochemical quartz crystal microbalance (EQCM) measurement were used to monitor the ORC. procedure. It was found that the surface structure became more uniform in the presence of Ru(bpy)(3)(2+), and the surface roughness was decreasing with the increasing of Ru(bpY)(3)(2+) concentration, suggesting a simple and effective method to control the formation of nanostructure on the gold surface.

Effect of pretreatment of black carbon on electrocatalytic activity of Pt/C catalyst for methanol oxidation

Direct methanol fuel cell (DMFC) has attracted wide attention due to its many advantages. However, its practical application is limited by the low electrocatalytic activity of the anodic Pt/C catalyst usually used for the methanol oxidation. In this paper, in order to increase the electrocatalytic performance of the Pt/C catalyst for the methanol oxidation, the black carbon, usually used as the supporter, was pretreated with CO2, air, HNO3 or H2O2. The cyclic voltarnmetric results indicated that the current densities of the anodic peak of methanol oxidation at the Pt/C catalysts with the black carbon pretreated with CO2,air, HN03, H202 and untreated black carbon were 39, 33, 32, 20 and 18 mA center dot cm(-2), respectively, illustrating that among the above five kinds of the Pt/C catalysts, the Pt/C catalyst with the black carbon pretreated with CO2 shows the best electrocatalytic activity and stability for the methanol oxidation. Its main reason is that the CO2 pretreatment could reduce the content of the oxygen-containing groups on the surface of the black carbon and increase the content of graphite in the black carbon, leading to the low resistance of the black carbon and the increase in the dispersion extent of the Pt particles in the Pt/C catalyst.

The electrocatalytic oxidation of ascorbic acid on polyaniline film synthesized in the presence of camphorsulfonic acid

Polyaniline-camphorsulfonic acid (PAN-CSA) composite film on platinum electrode surface has been synthesized via the electrochemical polymerization of aniline in the presence of camphorsulfonic acid (CSA). It was found that the doping of polyaniline (PAN) with CSA extends the electroactivity of PAN in neutral and even in alkaline media. The PAN-CSA composite film coated platinum electrodes are shown to be good electrocatalytic surfaces for the oxidation of ascorbic acid (AA) in phosphate buffer solution (PBS) of pH 7.0. The anodic peak potential of AA shifts from 0.63 V at the bare platinum electrode to 0.34 V at the PAN-CSA composite modified platinum electrode with a greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5-50 mM using cyclic voltammetry. The kinetics of the catalytic reaction are investigated using rotating disk electrode voltammetry and chronoamperometry. The results are explained using the theory of electrocatalytic reactions at chemically modified electrodes. The PAN-CSA composite on the electrode surface shows good reproducibility and stability.

Electrooxidation of COad intermediated from methanol oxidation on polycrystalline Pt electrode

The poisonous intermediate of methanol oxidation on a Pt electrode was validated to be COad by electrochemical method. An approximate treatment to bimolecular elementary reactions on an electrode was advanced and then was applied to the stripping normal pulse voltammetry (NPV) for complex multistep multielectron transfer processes on plane electrodes to study the kinetics of completely irreversible process Of COad oxidation to CO2. The kinetic parameters for this process, such as standard rate constant (0) and anodic transfer coefficient (alpha) for this irreversible heterogeneous electron-transfer process at electrode/solution interface and apparent diffusion coefficient (D-app) for charge-transfer process within the monolayer of COad on electrode surface, were obtained with stripping NPV method. The effect of the approximate treatment on the kinetic parameters was also analyzed.

A carbon-supported Pd-P catalyst as the anodic catalyst in a direct formic acid fuel cell

In this paper, it is reported for the first time that a carbon-supported Pd-P (Pd-P/C) catalyst for the anodic catalyst in the direct formic acid fuel cell (DFAFC) can be prepared. The Pd-P/C catalyst shows that its electrocatalytic activity and especially its stability for the oxidation of formic acid are much higher than that of a Pd/C catalyst. Therefore, the Pd-P/C catalyst may have practical applications in DFAFCs.

Structure-activity relationship of surfactant for preparing DMFC anodic catalyst

Three kinds of surfactants as stabilizer were applied to the preparation of electrocatalysts for direct methanol fuel cell (DMFC). The catalysts have been characterized by examining their catalytic activities, morphologies and particle sizes by means of cyclic voltammetry, chronoamperometry, X-ray diffraction and transmission electron microscopy (TEM). It is found that the surfactants with different structures have a significantly influence on the catalyst shape and activity. The catalysts prepared with non-ionic surfactants as the stabilizer show higher activity for direct oxidation of methanol. The structure-activity relationship (SAR) analysis has been explored and the effect of hydrophile-lipophile balance (HLB value) has also been discussed.

Physical and electrochemical characterizations of PtRu/C catalysts by spray pyrolysis for electrocatalytic oxidation of methanol

In this paper, it was reported that the carbon-supported Pt-Ru(Pt-Ru/C) catalyst used as the anodic catalyst in the direct methanol fuel cell (DMFC) was synthesized with a two-step spray pyrolysis (SP) method using the Pt and Ru metal salt as the precursors and polyethylene glycol (PEG) with the different molecular weights (Mw= 200,600,and 1000 analytical reagent) as cosolvent. PEG as a cosolvent plays a crucial role in producing PtRu/C catalysts. It was found that the Mw of PEG could affect the electrocatalytic activity of Pt-Ru and the morphology of the Pt-Ru particles in the Pt-Ru/C catalysts prepared with this method. When the Mw of PEG is 600, the Pt-Ru particles in the Pt-Ru/C catalyst prepared with this method possess the small average size, narrow size distribution, uniform dispersion, and high electrochemically active specific surface area. The electrocatalytic activity of the Pt-Ru/C catalyst prepared with this method using the cosolvent PEG with Mw = 600 for the methanol oxidation is much higher than that of the commercial E-TEK Pt-Ru/C catalyst. Therefore, the two-step SP method is an excellent method for the preparation of the Pt-Ru/C catalyst used in DMFCs.

Electrocatalytic oxidation of NADH by rutin in biomembrane-like films on glassy carbon electrode

Stable lipid film was made by casting dipalmitoylphosphatidylcholine (DPPC) and rutin onto the surface of a glassy carbon (GC) electrode. The electrochemical behavior of rutin in the DPPC film was studied. The modified electrode coated with rutin gave quasi-reversible reduction-oxidation peak on cyclic voltammogram in the phosphate buffer (pH 7.4). The peak current did not decrease apparently after stored at 4 degreesC for 8 hours in refrigerator. This model of biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by rutin. Rutin in the film acts as a mediator. The modified electrode shows a great enhancement and the anodic peak potential was reduced by about 220 mV in the oxidation of 5 X 10(-3) mol L-1 NADN compared with that obtained at a bare glassy carbon electrode. (C) 2000 Elsevier Science S.A. All rights reserved.

Electrocatalytic oxidation of ascorbic acid by ferrocene in lipid film cast on a glassy carbon electrode

A ferrocene-dimyristoyl phosphatidylcholine (DMPC) film electrode was prepared by casting the solution of ferrocene and DMPC in chloroform onto a glassy carbon electrode surface. Ferrocene retained in the biological membrane gave a couple of irreversible peaks of cyclic voltammogram. The electrode exhibited good electrocatalytic activity for the oxidation of ascorbic acid (H(2)A) in phosphate buffer (pH 6.64) with an anodic peak potential of +340 mV (vs. Ag/AgCl). The anodic current was directly proportional to the square root of the scan rate below 150 mV s(-1). The influence of the pH value was investigated and it was observed that pH 6.64 was the suitable value to the anodic peak potential and current. The thickness of the film and the interference of uric acid were also studied. The electrode can be used to determine H(2)A in the presence of equimolar uric acid. The catalytic peak current increased linearly with the concentration of H(2)A in the range of 1 X 10(-4)-5 X 10(-3) mol L-1.

Electrocatalytic oxidation of ascorbic acid by norepinephrine embedded in lipid cast film at glassy carbon electrode

A stable lipid cast film was made by casting a lipid in chloroform onto a glassy carbon electrode. We imbedded a new mediator norepinephrine into this lipid cast film, which was considered as a biological membrane model. Through electro catalytic oxidation of ascorbic acid by this system, the anodic overpotential was reduced by about 250 mV compared with that obtained at a bare glassy carbon electrode. The electrochemical behavior of norepinephrine in the cast film was controlled by diffusion. The obtained diffusion coefficient of ascorbic acid was 1.87 x 10(-5) cm 2 s(-1). The catalytic current increased linearly with the concentration of ascorbic acid in the range from 0.5 to 10 mM. Using cyclic voltammetry, we obtained two peaks for ascorbic acid and uric acid in the same solution. The separation between the two peaks is about 147 mV. (C) 2001 Elsevier Science Ltd. All rights reserved.

Oxidation of NADH by dopamine incorporated in lipid film cast onto a glassy carbon electrode

Stable lipid film was made by casting lipid in chloroform onto a glassy carbon electrode. This model of a biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by dopamine. After this electrode had been immersed in dopamine solution for 10 h, it was found that some dopamine had been incorporated in the film. The cyclic voltammogram was obtained for the oxidation of 2.0 X 10(-3) mol 1(-1) NADH with dopamine incorporated in the films. All electrochemical experiments were performed in 0.005 mol 1(-1) phosphate buffer (pH 7.0) containing 0.1 mol 1(-1) NaCl without oxygen. The oxidation current increased gradually with successive sweeps and reached steady state. It was a different phenomenon from previous results. The anodic overpotential was reduced by about 130 mV compared with that obtained at a bare glassy carbon electrode. The diffusion coefficient for 2.0 X 10(-3) mol 1(-1) NADH was 6.7 X 10(-6) cm(2) s(-1). (C) 1999 Elsevier Science S.A. All rights reserved.

In situ microscopic FTIR spectroelectrochemistry study of oxidation of L-ascorbic acid in polymer electrolyte (PEG/LiClO4)

In situ microscopic FTIR spectroelectrochemistry behavior of L-ascorbic acid (H(2)A) in polymer electrolyte is reported for the first time. H(2)A undergoes a two-step oxidation, The oxidation waves shift towards more anodic potential values when the scan rate increases. The peak currents of the oxidation waves are proportional to the square roots of scan rate up to 100 mV/s, The in situ infrared spectra suggest that the product of the oxidation be dehydroascorbic acid, which may exist as a dimer.

ELECTROCATALYTIC OXIDATION OF REDUCED NICOTINAMIDE COENZYMES AT ORGANIC DYE-MODIFIED ELECTRODES

Chemically modified electrodes (CMEs) were prepared by adsorbing different dyes, including methylene blue (MB), toluidine blue (TB) and brilliant cresyl blue (BCB), onto glassy carbon electrodes (GCE) with anodic pretreatment. The electrochemical reactions of adsorbed dyes are fairly reversible at low coverages. The CMEs are more stable in acid solutions than in alkaline ones, which is mainly due to decomposition of the dyes in the latter media. They exhibit an excellent catalytic ability for the oxidation of nicotinamide coenzymes (NADH and NADPH). The formation of a charge transfer complex between the coenzyme and the adsorbed mediator has been demonstrated using a rotating disk electrode. The charge transfer complex decomposition is a slow step in the overall electrode reaction process. Some kinetic parameters are estimated. Dependence of the electrocatalytic activity of the CMEs on the solution pH is discussed.

PREPARATION OF PERIODATOCUPRATE(III) AND TELLURATOCUPRATE(III) BY ELECTROCHEMICAL AND OZONE OXIDATION

In the cyclic voltammograms of complexes with periodate and tellurate, the anodic and cathodic peaks were observed evidently for Cu(III)/Cu(II) couples in caustic potash aqueous solutions. Copper(III) complexes were obtained by utilizing ozone as oxidant