Marek Szklarczyk

The behaviour of iron electrode in CO2− saturated neutral electrolyte—I. Electrochemical study

Abstract The properties of iron electrode in CO2-saturated sodium chloride supporting electrolyte were investigated by cyclic voltammetry of static and rde-Ferrovac electrode in the potential region from −1.1 to −0.3 V (nhe). In addition to the reduction of H3O+ ions formed due to the protolysis of carbonic acid, the direct (activated) reduction of both H2CO3 molecules and HCO−3 ions was observed. It is proposed that catalytic, ErC′i mechanism accounts for the occurrence of the latter processes.

The behaviour of high polar organic solvents on platinum electrodes—I. The study of adsorption and electrode reactions of dimethylsulphoxide

Abstract The adsorption of dimethylsulphoxide and reactions of adsorbed molecules at platinized platinum electrode were studied by potentiodynamic and radiometric techniques. The adsorption of dimethylsulphoxide is described by Temkin type isotherm. The adsorbed dimethylsulphoxide is reduced in two steps to dimethylsulphide in the hydrogen range of potentials and oxidized to dimethylsulphone above 0.6 V. The latter product is desorbed from the surface of the electrode.

The study of electrode processes of sulphur dioxide on platinized electrode by the radiochemical method

Abstract The adsorption of sulphur dioxide and the electrode reactions of adsorbed molecules at a platinized platinum electrode were studied by potentiodynamic and radiometric techniques. The surface concentration of adsorbed species as well as the charges of their reduction and oxidation were determined. Sulphur adatoms and platinum sulphides as products of sulphur dioxide adsorption in “double-layer” and hydrogen regions of potentials are proposed respectively. The obtained results were compared with data of other authors.

The behaviour of high polar organic solvents at platinum electrode — II. Adsorption and electrode reactions of acetonitrile

Abstract The adsorption of acetonitrile and reduction of adsorbed molecules at platinized platinum electrode were studied by potentiodynamic and radiometric techniques. During acetonitrile adsorption the reversibly and irreversibly adsorbed species are formed. One electron reduction process occurs in the potential range 0.45-0.15 V. Below 0.15 V the deeper reduction of adsorbed acetonitrile takes place — the final products are ammonia and ethane. The differences of smooth and platinized platinum electrodes properties are briefly discussed.

The behaviour of iron electrode in CO2− saturated neutral electrolyte—II. Radiotracer study and corrosion considerations

The radiotracer method described previously was applied for investigations of adsorption processes occuring in the system: iron electrodeposited electrode and CO2-saturated (14C-labelled) neutral electrolyte. In addition to adsorption of 14C-containing species in the electrodeposited film, both reversible and irreversible adsorption of those species was identified. The irreversible adsorption was interpreted to result from incorporation of 14C-species (most probably HCO−3 ions) to the passive layer formed on the iron electrode. The reversible adsorption was concluded to occur due to the weak interactions of carbonic acid with the oxidized iron surface. Lewis acid and base concept of adsorption was used to account for the results. The role of the reversible adsorption process in the accelerated corrosion of steel due to the presence of carbon dioxide in aqueous solutions is discussed.

Interaction of thiourea with silver electrodes

Abstract Adsorption and surface reactions of thiourea on silverized silver electrodes have been studied in 0.1 M HClO4 and 0.1 M NaClO4. Quantitative radiometric data obtained using 14C-labeled thiourea indicate that adsorption of thiourea takes place in the entire range of potentials accessible to surface studies on silver electrodes in the acidic and neutral solutions. The values of the thiourea surface concentration are very high, close to the maximum monolayer packing densities calculated from the molecular size of thiourea (ca. 6 × 1014 molecules cm2). Reorientation of adsorbed molecules from perpendicular to parallel to the surface is a possible reason for the decrease in Г at potentials located on the positive side of the adsorption maximum. As shown by the surface/bulk-exchange experiments, adsorption is reversible in the potential range preceding and directly following the adsorption maximum. In this range, the surface process can be quite accurately described by the Frumkin adsorption model. When corrected for water displacement, the calculated value of the Gibbs energy of adsorption points to strong adsorption of thiourea on silver (chemisorption). At the most positive potentials, surface processes become irreversible, ultimately leading to the formation of chemisorbed sulfur-containing species that act as the electrode poison. Depending on the solution pH, an addition of chloride to the cell has different effects on the adsorption of thiourea. As a result of the Cl−-caused reorientation of the adsorbate, the surface concentration of thiourea increases in the neutral solution. The opposite effect occurs in the acidic solution, where surface blocking by adsorbed chloride plays a dominant role.

The Pt-acetone-water system investigated by radiotracer and electrochemical methods

Abstract The adsorption of acetone on a platinum electrode from aqueous acidic solutions, as well as the behaviour of tritiated water in the platinum/acetone (water) interface were investigated by the radiotracer method and by cyclic voltammetry. The π-electron complex formation between platinum and acetone is followed by the surface polymerization (condensation) of this compound—the length of the surface chain depends on the bulk concentration of acetone. The earlier data of some other authors indicating that the hydrogen isotope exchange between adsorbed acetone and the acidic electrolyte occurred, are confirmed. The counting rates originating from the tritium atoms incorporated in the acetone adsorbed phase due to the isotope exchange have previously been interpreted (Schultze) as occurring from tritiated water chemisorbed on platinum. The prospects for the investigation of water adsorption on platinum by the use of radiotracer methods under electrochemical conditions are discussed.

The behaviour of high polar organic solvents at platinum electrode—III. the study of adsorption and electrode reactions of N, N-dimethylformamide

Abstract The adsorption of N,N -dimethylformamide and oxidation of adsorbed species at platinized platinum electrode in 0.5 M aq H 2 SO 4 were studied by potentiodynamic, potentiostatic and radiometric techniques. It was shown, that adsorption occurs with decomposition of DMF molecule. Below 0.15 V the adsorbed species are desorbed from the electrode surface. The kinetics of adsorption and oxidation of DMF are described by Langmuire type relation. The mechanism of adsorption of DMF as well as oxidation of adsorbed products has been considered.

Electrical Breakdown of Liquids

A phenomenon generally referred to as dielectric breakdown or electrical breakdown is an increase in conduction of a material by several orders of magnitude resulting from the failure of dielectrics under electric stress. The parameter which describes the quality of material as a dielectric from the point of view of electrical breakdown is the voltage at which the process occurs, divided by the dielectric thickness. It is loosely referred to by such terms as the breakdown field strength, dielectric strength, or instrinsic electrical strength. The magnitude of such a strength depends upon the composition and structure of the dielectric, but, in addition, is often a function of the multiplicity of external variables such as the uniformity of the electrical field, the heating effects caused by long stress times, and the quality of electrodes between which the dielectric is placed.

SERS of dimethyl sulphoxide on silver electrodes and on silver chloride sol

Abstract The surface enhanced Raman spectra of dimethyl sulphoxide were observed on polycrystalline silver electrodes. Spectra of similar intensities were recorded for electrode surfaces activated by the oxidation-reduction cycle and by scanning only within the range of more negative potentials. The micrographs obtained by scanning electron microscopy indicated that both surfaces are rough. In the case of an anodized silver electrode in a chloride medium, the SERS spectrum could be superimposed on the bulk DMSO spectrum enhanced by interaction with particles of silver chloride sol produced during the oxidation-reduction cycle.