ELECTROCHEMICAL-BEHAVIOR OF SOME CHELATE AMINOCARBOXYLATE COMPLEXES OF COBALT IN AQUEOUS-SOLUTIONSстатья
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Дата последнего поиска статьи во внешних источниках: 27 мая 2015 г.
Аннотация:Electrochemical behavior of cobalt iminodiacetate, nitrilotriacetate, and (ethylenediamine)tetraacetate (Coida . 2H2O, NaConta . 2H2O, and NaCoedta . 2H2O, respectively) on Hg, Au(Hg), Au, Ag, Pt, Pt(Hg), and vitreous carbon was studied by polarography, voltammetry, and rotating disk electrode techniques. It was shown that electrooxidation of [Coida]0 at the mercury electrode was complicated by mercury dissolution and that the processes with [Coida]0 and [Conta]- participation occurred with pronounced overpotential at Au-, Pt-, Ag-, and vitreous carbon electrodes and were due to electrochemical transformations of the ligand. The transfer coefficient alpha and the rate constant k(alpha = 0.5, logk = -3.17 +/- 0.02) were determined for [Coedta]- electroreduction at Au(Hg). It was found that solution pH did not affect the [Coedta]- electroreduction rate at Au(Hg) and Hg over the entire range of reagent stability. The electrostatic retardation of this process was not observed at the negative surface charges at Hg. The retardation of this process was observed for the Au and Pt electrodes in a wide potential range. This retardation appears to be a result of ligand adsorption, which accumulates near the surface due to the difference in the stability constants of the reagent [Coedta]- and the product [Coedta]2-. The analysis of corrected Tafel dependence of [Coedta]- electroreduction on Au(Hg) allows us to make the conclusion that the center of discharging species [Coedta]- in transition state is localized at the outer Helmholz plane.