A. G. Pshenichnikov

Gas-generating porous electrodes: Chlorine generation in DSA at low and intermediate overpotentials

Parameters of gas-generating porous electrodes (GPE) in the range of low overpotentials, where all the pores are filled with electrolyte and the gas generation and transport occur in an internal diffusion mode, are calculated and analyzed. A criterion for estimating critical overpotential values, upon achieving which first gas pores start appearing in GPE, is found. Theoretical critical overpotentials of chlorine generation in DSA satisfactorily agree with experiment. About 20% of porous space takes part in the chlorine generation in DSA of “standard” thickness (5 μm), provided there are no limitations on chlorine transport outside the electrode. The appearance of the “low-polarizability” part in the anodic branch of polarization curve for DSA is caused by the appearance, in GPE, of a system of gas pores connected with each other and the front electrode surface. This assumption is partially confirmed by theoretical estimation.

Surface Properties of Nickel Electrodes in an Alkaline Electrolyte: An Ellipsometry Study

Adsorption of oxygen-containing species (OCS) on a polycrystalline nickel electrode in an alkaline electrolyte is studied by electrochemical and ellipsometric methods in the potential region from hydrogen evolution to oxygen evolution. It is concluded that OCS have stoichiometric composition Ni(OH)2 up to 1.35 V. The potential of the OCS formation onset, the oxide monolayer thickness, and the surface coverage by OCS in the interval 0 ≤ θ ≤ 1 are determined. The oxidation and reduction of a nickel oxide layer, repeatedly cycled at 1.35–1.5 V, suggests that this process is chemically reversible and the thickness of the oxide formed at 1.35 V is constant. It is shown that keeping the electrode under open-circuit conditions at 0.7–0.9 V for 10–20 h leads to the formation of nonelectroconducting oxide “NiOz.”

Adsorption of 1-(2-propionitrile)-pyrrolidine (PNP) and electrochemical behavior of product of PNP adsorption on smooth platinum

The adsorption of 1-(2-propionitrile)-pyrrolidine (PNP) on a polycrystalline smooth platinum electrode in 0.5 M H2SO4 is studied. It is found that PNP is adsorbed practically irreversibly. The time dependence of Pt coverage by the organic substance in semilogarithmic coordinates is linear and is approximated by the Roginskii-Zeldovich equation. The calculated rate constant of PNP adsorption kads = 0.069 mol−1s−1. The product of PNP adsorption is electrochemically active in the range of potentials of Er = 0.45−0.67 V. Kinetic parameters of the process are determined. The following overall equation is suggested for its description: RCNads + 2H+ + 2e ⇆ RCHNHads. The results obtained are compared with the data in PNP adsorption and properties of the product of PNP adsorption in alkaline solutions.