Enhancement of the electrooxidation of ethanol on Pt-Sn-P/C catalysts prepared by chemical deposition process

In this paper, five Pt3Sn1/C catalysts have been prepared using three different methods. It was found that phosphorus deposited on the surface of carbon with Pt and Sn when sodium hypophosphite was used as reducing agent by optimization of synthetic conditions such as pH in the synthetic solution and temperature. The deposition of phosphorus should be effective on the size reduction and markedly reduces PtSn nanoparticle size, and raise electrochemical active surface (EAS) area of catalyst and improve the catalytic performance. TEM images show PtSnP nanoparticles are highly dispersed on the carbon surface with average diameters of 2 nm. The optimum composition is Pt3Sn1P2/C (note PtSn/C-3) catalyst in my work. With this composition, it shows very high activity for the electrooxidation of ethanol and exhibit enhanced performance compared with other two Pt3Sn1/C catalysts that prepared using ethylene glycol reduction method (note PtSn/C-EG) and borohydride reduction method (note PtSn/-B). The maximum power densities of direct ethanol fuel cell (DEFC) were 61 mW cm(-2) that is 150 and 170% higher than that of the PtSn/C-EG and PtSn/C-B catalyst.

WO3/C hybrid material as a highly active catalyst support for formic acid electrooxidation

The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nano-catalysts. The resultant Pd-WO3/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO3/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd.

Highly Active Carbon-supported PdSn Catalysts for Formic Acid Electrooxidation

PdSn/C catalysts with different atomic ratios of Pd to Sn were synthesised by a NaBH4 reduction method. Electrochemical tests show that the alloy catalysts exhibit significantly higher catalytic activity and stability for formic acid electrooxidation (FAEO) than the Pd/C catalyst prepared with the same method. XRD and TEM indicate that a particle-size effect is not the main cause for the high performance. XPS confirms that Pd is modified by Sn through an electronic effect which can decrease the adsorption strength of poisonous intermediates on Pd and thus promote the FAEO greatly.

The size-controlled synthesis of Pd/C catalysts by different solvents for formic acid electrooxidation

The size-controlled synthesis of Pd/C catalyst for formic acid electrooxidation is reported in this study. By using alcohol solvents with different chain length in the impregnation method, the sizes of Pd nanoparticles can be facilely tuned; this is attributed to the different viscosities of the solvents. The results show that a desired Pd/C catalyst with an average size of about 3 nm and a narrow size distribution is obtained when the solvent is n-butanol. The catalyst exhibits large electrochemically active surface area and high catalytic activity for formic acid electrooxidation.

Ethanol electrooxidation on Pt/C catalysts promoted with praseodymium oxide nanorods

The Pt/C electrocatalysts containing Pr6O11 nanorods were successfully prepared. By various electrochemical characterization methods, it was demonstrated that the Pr6O11 nanorods have an obviously promotive role for ethanol electrooxidation catalyzed by Pt/C. However, according to the stripping experiment, the promotive effect of Pr6O11 does not result from the easier electrooxidation of the intermediate adsorbate on Pt-Pr6O11/C than on Pt/C. It was supposed that Pr6O11 could promote a certain step in ethanol oxidation, and that the special morphology of the nanorods could further enhance the activity compared with nanoparticles.

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.

Electrooxidation of methanol on carbon nanotubes supported Pt-Fe alloy electrode

The synthesis and characterization of catalysts based on bimetallic materials, Pt-Fe supported on multi-walled carbon nanotubes (MWNTs) for methanol electrooxidation is reported here. The catalyst was prepared by a spray-cooling process and characterized by TEM, EDS, ICP and XRD. The electrocatalytic properties of the Pt-Fe/MWNTs electrode for methanol oxidation have been investigated by cyclic voltammetry and chronoamperometry. It presented higher electrocatalytic activity and stability than a comparative Pt/ MWNTs catalyst. This may be attributed to the addition of Fe which leads to the small average particle size and high utilization of Pt in the Pt-Fe/MWNTs catalyst. The results imply that the Pt Fe/MWNTs composite has good potential applications in fuel cells.

Effect of borohydride as reducing agent on the structures and electrochemical properties of Pt/C catalyst

In this paper, we found that boron deposited on the surface of support when sodium borohydride used as reducing agent during the preparation of Pt/C catalyst. The deposition of boron markedly reduces particle size of Pt, raises electrochemical active surface (EAS) area of catalyst and electrochemical activity for hydrogen evolution or oxygen reduction reaction (ORR) compared with which prepared using other reducing agents (hydrogen and formaldehyde).

The relation between formal potential and structure of indophenols and molecular mechnism of electrooxidation

The molecular structural parameters of indophenol and its derivatives were calculated by semi-empirical molecular orbital quantum chemical method,The relation between molecular structural parameters and formal potentials was analyzed by principal factor analysis and multiple Linear regression method. It was found that the formal potential of indophenols has a good relation with two-center electron exchange energy, E-ex (2), resonance energy of O-C bond, E-ex (C-1-O), and molecular ionization potential, I-p, among 19 moleclular structural parameters. The regression equation is E-0' = 1. 47 x 10 (-3) E-ex (two) - 5. 74 x 10 (-2) E-ex (C-1 - O) - 1. 41 x 10 (-2) I-p with RC = 0. 9999 and SD = 0. 00424. It was confirmed by the relation between structure parameters and formal potentials, and the thermodynamic stability of its intermediate products that the H (+) ionization is prior to the electron transfer step in the oxidation mechanism.

ELECTROOXIDATION OF A CHLORIDE COMPLEX OF PLATINUM(II) AT A GLASSY-CARBON ELECTRODE

The electro-oxidation of PtCl42- was studied on a glassy carbon (GC) electrode. A Pt(IV) complex was formed on the electrode surface through coordination to the oxygen atom of an oxide functional group on the electrode, which results in its deactivation. The ferri/ferrocyanide redox couple was used as a probe to examine the activity of the GC electrode. X-ray photoelectron spectroscopy was employed to characterize the platinum on the electrode surface, and showed that the oxidation state of the Pt element changes depending on the electrochemical treatment of GC electrode. The platinum complex on the surface of the GC electrode can be transformed to Pt-0 by cycling the electrode between -0.25 and +1.65 V/SCE in 0.1 M H2SO4 solution. The above procedure can be used to disperse platinum ultramicroparticles on the surface of a GC electrode.

INVESTIGATION ON MECHANISMS FOR THE ELECTROOXIDATION OF SOME BILE-PIGMENTS BY SPECTROELECTROCHEMISTRY

The electrooxidation behavior of bilirubin (BR), biliverdin (BV), purpurin (Pu), and choletelin (Ch in dimethylformamide (DMF) have been investigated bv voltammetry, in situ electron spin resonance (ESR) thin-layer spectroelectrochemistry and especially i

ELECTROOXIDATION OF ASCORBIC-ACID AT THE BIS(4-PYRIDYL) DISULFIDE MODIFIED GOLD ELECTRODE

The electrooxidation of ascorbic acid (AA) at the bis(4-pyridyl)disulfide (PySSPy) modified gold electrode was studied. The results showed that the oxidation process was pH-dependent. It was mainly due to the static interaction between AA and the modified