2018-Sustainable Industrial Processing Summit
SIPS2018 Volume 2. Amatore Intl. Symp. / on Electrochemistry for Sustainable Development
| Editors: | F. Kongoli, H. Inufasa, M. G. Boutelle , R. Compton, J.-M. Dubois, F. Murad |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2018 |
| Pages: | 216 pages |
| ISBN: | 978-1-987820-84-3 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Estimation of the Lability of Electrochemical Systems Involving Processes with Chemical Stages
Arvydas Survila1; Stasė Kanapeckaitė1; Kęstutis Mažeika1;1CENTER FOR PHYSICAL SCIENCES AND TECHNOLOGY, Vilnius, Lithuania;
Type of Paper: Regular
Id Paper: 234
Topic: 47
Abstract:
Lability of electrochemical systems is one of the substantial characteristics for determining kinetics of the processes involving chemical steps. <br />A sufficiently rigorous quantitative estimate of this parameter is possible only for the preceding reactions of the first or pseudo-first order [1]. For more complex systems, such as solutions of metal complexes, there are no analytical expressions. To get around this obstacle, we analyzed the concentration profiles simulated using differential diffusion equations supplemented by the corresponding kinetic terms [2].<br />In the case of high lability, interrelation between concentrations of species is specified by stability constants of metal complexes. The certain deviations from equilibrium distribution are observed in the diffusion layer for less labile systems. In default of the electrically active complex, the reaction layer concept can be applied and used in the electroanalysis.<br />LPS voltammetric data obtained for hydrogen evolution on copper electrode in weakly acidic glycine solutions were used as basis for estimation of electrochemical lability of different glycine species. The dependence of current peaks on both solution pH and glycine concentration and the convolution of voltammograms show that only some protonated glycine species can act as labile proton donors in hydrogen evolution, since protons attached to different groups in glycine molecule exhibit different mobility. In contrast to protonated amino group, the release of proton from carboxylic group proceeds significantly faster. Consequently, protonated <sup>+</sup>H<sub>3</sub>N-CH<sub>2</sub>-COOH species can be treated as labile proton donors, whereas zwitterions <sup>+</sup>H<sub>3</sub>N-CH<sub>2</sub>-COO<sup>-</sup> do not fall into this category.