Kinetics and Mechanism of Zn(II) Ions Electroreduction Catalyzed by Organic Compounds

Abstract

The paper describes the results of the studies of organic substances catalytic activity on Zn(II) ions electroreduction on mercury in perchlorate solutions. Zn(II) ions electroreduction in the presence of catalyzing substance proceeds in two one-electron stages. The first electron transfer is the stage determining the process rate. All catalyzing substances increase the rate of first electron transfer. The acceleration effect is connected with the stability of active complexes formed on the electrode surface. The rate of the second electron transfer depends mainly on the adsorption of the catalyzing substance on the electrode surface -of the surface excess and the structure of the adsorption layer. Hence the second electron transfer can be inhibited or catalyzed. The mechanism of the organic substance catalytic activity is also given.

Catalytic activity of thiourea and its selected derivatives on electroreduction of In(III) in chlorates(VII)

“…Probably the magnitude of the catalytic effect is connected to the equilibrium of reaction of active complexes formation before the transfer of consecutive electrons. A similar effect was observed by Dalmata [61] in his study on the catalytic activity of organic substances on the electroreduction process of Zn(II).…”

The Catalytic Impact of Ethionine on the Multi-Step Electroreduction of Bi(III) Ions in Chlorates(VII) Solutions

“…Studies on the kinetics of various depolarisers in the presence of electrode substances are comprehensively discussed in the literature [5][6][7][8][9][10][11]. It was demonstrated that the structures of the inter-phase area caused by adsorption of organic compounds on the surface of mercury play a significant role in the mechanism of the cap-pair effect.…”

Selective, Simple and Economical Method for the Voltammetric Determination of Bi(III) in the presence Cystine in Non – Complexing Solution

“…The presented results allow for the following conclusions: -cystine, in accordance with cap -pair rule (Sykut 1978) (Dalmata 2005), accelerates the electroreduction of Bi(III) ions in chlorates (VII) solutions -the reversibility of Bi(III) ions electroreduction in chlorates (VII) depends on the cystine concentration and water activity -the optimal concentration of cystine and water activity for Bi(III) determination by voltammetric method were established. The presented method is fast, simple, relatively inexpensive and with easily accessible measurement system.…”

“…In agreement with cap -pair effect (Sykut 1978) (Dalmata 2005) the organic substances introduced to the supporting electrolyte can catalyze one type of electrode processes and simultaneously have no influence or even inhibit the other electrode processes. Such behaviour enables the determination of different elements near each other without necessity of analyte accumulation, what considerably simplifies the analysis procedure.…”