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

Abstract

It was concluded that the presence and the protonation of the ethionine (Et) have effects on the rate of the multistep process of Bi(III) electroreduction in the 2 mol dmchlorates(VII). The catalytic activity of ethionine increases with increasing amounts of NaClO 4 in the basic electrolyte solution. Increased amounts of HClO 4 in chlorate(VII) solutions causes a decreased rate of the Bi(III) ion electroreduction process in the presence of ethionine. This confirms the assumption on the variety of active complexes mediating the passage of electrons.

The Effect of Protonated Ethionine Adsorption on Bi(III) Electroreduction in Chlorate(VII) Solutions with Varied Water Activity

“…Moreover, one can observe that the increase of NaClO 4 concentration in the chlorate (VII) solution has the effect on the shift of E z values towards positive potentials, but the HClO 4 concentration increases towards more negative potentials. These changes, depending on the ethionine protonation degree in the studied chlorate (VII) solution, point out to reorganization of amino acid molecules on electrode surface [19][20][21]. The linear dependences E z = f(logc ethionine ), obtained for all studied concentrations of chlorate (VII), indicate the specific adsorption of the amino acid on the electrode surface [28].…”

“…A significant effect of ethionine on the changes of the parameters of the Hg/chlorate (VII) interface double layer was observed [21]. The course of the differential capacity curves on mercury in the chlorate (VII) solutions depends also on the changes in the HClO 4 /NaClO 4 concentration ratio in the basic electrolyte and water activity (Fig.…”

“…It was found that an essential role in the electrode process acceleration is played by the ability of organic substance, undergoing adsorption on the electrode, to form complexes with the depolarizer in the circum electrode layer and location of the depolarizer reduction potential in the area of labile adsorption equilibrium of the organic substance [7,12]. The previous studies proved a significant effect of water activity [13], some amino acids [14][15][16][17], and change of the protonation of the amino acids on mechanism and kinetics of Bi(III) ions electroreduction [18][19][20][21], which developed the interpretation of the Bcap-pair^effect mechanism [11].…”

“…It was concluded that the presence and the protonation of ethionine affect the rate of the multistep process of Bi(III) electroreduction in 2 mol dm −3 chlorates (VII) [21]. The mechanism of the catalytic effect of ethionine is associated with the formation of complexes under specific conditions existing on the electrode surface.…”

“…Ethionine adsorption favors formation of these complexes. Changes of adsorption parameters at the Hg/chlorate (VII) interfaces are affected by the total charge of the adsorbate molecule which is a result of pH solution [21][22][23].…”