Shaojun Dong

Electrochemical and electrocatalytic properties of iron(III)-substituted Dawson-type tungstophosphate anion

The electrochemical and electrocatalytic properties of iron(III)-substituted Dawson-type tungstophosphate anion are described. The anion exhibits a one-electron couple associated with the FeIII center and two two-electron waves attributed to redox processes of the tungsten-oxo framework. All three waves are pH dependent. The anion has a catalytic effect on the reduction of H2O2 and NO2−. The rate constant of the reaction of [P2W17O61(FeII · OH2)]8− with H2O2 was measured using an ultramicroelectrode and was found to be 1.16 × 104 M−1 s−1, which is one order of magnitude higher than the reported value for the reaction of H2O2 with iron-substituted Keggin-type heteropoly anion.

Electrochemical study of isopoly- and heteropolyoxometallates film modified microelectrodes. I: Pretreatment and modification of the Mo8O4-26 modified carbon fiber microelectrode

In this paper the preparation of isopoly- and heteropolyoxometallates (IPA and HPA) thin film modified carbon fiber (CF) microelectrodes and the factor that influences the modification of IPA and HPA films are described. IPA and HPA film modified CF microelectrodes can all be prepared by cyclic potential scan and simple dip coating. The modified electrodes prepared are very stable and reversible in acidic solution with monolayer characteristics. The electrochemical pretreatment of CF microelectrodes plays an important role in the modification of IPA and HPA film. The absorption of IPA and HPA film on electrode surfaces has been discussed on the basis of surface conditions of the CF microelectrode and the structure of IPA and HPA.

Research on chemically modified electrodes: Catalytic reduction of dioxygen at a cobalt phthalocyanine-doped polyaniline film electrode

Abstract The electrochemical incorporation of tetrasulphonated cobalt phthalocyanine (TSPcCo) into a polyaniline film was studied by XPS, SEM and cyclic voltammetry. The TSPcCo-doped polyaniline film modified glassy carbon electrode shows very good catalytic activity and stability for dioxygen reduction. The peak potential of dioxygen reduction at the modified electrode shifted to more positive values with an increase in the film thickness. The RRDE experiments indicated that only two-electron reduction of dioxygen to H 2 O 2 occurred at the modified electrode in acidic solutions. No further reduction of H 2 O 2 was observed at the modified electrode with increasing film thickness. It was proved by an RDE experiment that the catalytic reduction of dioxygen at the electrode is rather complex and is controlled by several kinetic factors. The kinetic currents can be described by an imitated form of the Koutecký-Levich equation. The actual kinetic equation can be inferred from a set of plots of the experimental data. Therefore the relative kinetic currents can be calculated.

ELECTROCATALYSIS AT A MICRODISK ELECTRODE MODIFIED WITH A REDOX SPECIES

Abstract The current equation of the electrocatalytic reaction at a microdisk electrode modified with redox species has been described and verified experimentally. There exists a linear relationship between plateau limiting current and the radius of the microdisk electrode for a catalytic process. The influence of the dimensions of the microdisk electrode on catalytic efficiency is discussed. The polyvinylferrocene (PVFc)-modified microdisk electrode prepared by the coating method was taken as a typical example, on which the electrocatalytic oxidation of ascorbic acid could be studied. The catalytic reaction rate constants were determined as an average value of 1.5 × 10−7 cm3/mol s by this method, and are consistent with those obtained at a conventional electrode.

Electrochemical behaviour of Fe(CN)63−/4− redox ions in a polypyrrole film

Abstract Using potassium ferrocyanide as the supporting electrolyte, we polymerized pyrrole electrochemically in an aqueous solution and injected Fe(CN) 6 3−/4− redox ions into the polypyrrole. The electrochemical behaviour of the Fe(CN) 6 3−/4− redox ions in polypyrrole was influenced by the nature of the cations of the supporting electrolyte, the concentration of the supporting electrolyte and the thickness of the polypyrrole film.

Electrocatalytic oxidation of ascorbic acid at a Prussian Blue film modified microdisk electrode

The preparation and the behaviour of a Prussian Blue (PB) film on a platinum microdisk electrode has been described. Electrocatalytic oxidation of ascorbic acid has occurred at the PB film modified microelectrode. This shows a typical example of a modified microelectrode in electrocatalysis following our previous theoretical studies (J. Electroanal. Chem., 309 (1991) 103) and the related catalytic reaction rate constant was determined.

Direct electrochemical reactions of cytochrome c at iodide-modified electrodes

Quasi-reversible and direct electron transfer was observed between an iodide-modified Au electrode and cytochrome c, as well as between cytochrome c in an iodide-containing solution and a bare Au electrode. The results suggest that an electrostatic intera

CYCLIC VOLTAMMETRIC AND SPECTROELECTROCHEMICAL STUDIES OF COPPER IN ALKALINE-SOLUTION

The behaviour of the electroplated copper film electrode on tin oxide/glass or glassy carbon surface was studied in potassium hydroxide medium by cyclic voltammetry and in situ transmission spectroelectrochemistry. The results indicate that the electroplated copper film electrode is similar to a copper electrode and cyclic voltammetry with this electrode affords more resolution. The anodic peaks were found to correspond successively to the adsorption of oxygen, the formation of a surface layer of Cu2O, the formation of a surface layer of Cu(OH)2 or CuO and formation of a thick multilayer film of CuO. This is the first time it has been proposed that a surface layer of Cu(OH)2 or CuO is formed from the oxidation of the surface layer of Cu2O. Similarly, a clear interpretation is presented that the cathodic peaks correspond successively to the reduction of CuO to Cu2O, the reductions of Cu2O to Cu and the soluble Cu(II) species to Cu. On the other hand, a shoulder peak related to the chemical transformation of Cu(OH)2 to CuO was first observed.

PREPARATION AND PROPERTIES OF POLYPYRROLE FILM DOPED WITH A DAWSON-TYPE HETEROPOLYANION

Abstract The electropolymerization of pyrrole in the presence of Dawson-type tungstophosphate yields a polypyrrole (PPy) film doped with tungstophosphate anions on the electrode surfaces. The electrochemical behaviour of this film was described, and the stability and pH-dependence were also discussed. The tungstophosphate doped PPy film has a catalytic effect on the reduction of oxygen and gave an anodic shift of 150–200 mV for the reduction of oxygen.

Electrodeposition of platinum particles on glassy carbon modified with cobalt porphyrin and nafion film and their electrocatalytic reduction of dioxygen

Abstract In this paper, five types of chemically modified electrode (CMEs) prepared with the deposition of platinum particles on various surfaces of glassy carbon (GC) modified with cobalt porphyrin and Nafion® solution are characterized using the electron scanning microscope (SEM). Their activities in the four-electron reduction of dioxygen to water on the basis of their electrochemical data from cyclic voltammetric and rotating ring-disk electrode (RRDE) experiments are examined and compared. Platinum particles dispersed on the GC surface adsorbed with the cobalt porphyrin exhibit the highest activity for the electrocatalytic reduction of dioxygen. However it is interesting that the cobalt ion is lost from the center of the porphyrin ring during the preparation of the cobalt porphyrin + Nation mixture solution, while the porphyrin ring still remains in the Nation film, as shown by EDX analysis. The incorporation of the porphyrin may change the structure of the Nafion film into a looser form, since the platinum particles dispersed in the film are more readily exposed, resulting in more favourable mass transfer and higher activity for the electrocatalytic reduction of dioxygen.