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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Transformation of Complex LPS Voltammograms into Normalized Tafel Plots as Applied to Ligand-deficient Systems
Arvydas Survila1;1CENTER FOR PHYSICAL SCIENCES AND TECHNOLOGY, Vilnius, Lithuania;
Type of Paper: Regular
Id Paper: 198
Topic: 47
Abstract:
Voltammograms of the reduction of metal complexes obtained for ligand-deficient systems have certain features [1]. Steady-state curves contain pre-waves and the splitting of current maximum into two peaks is observed under linear potential sweep (LPS) conditions. Despite of the complex shape, their transformation into linear normalized Tafel plots (NTP) is possible. For this, the following procedures should be followed.
Since the kinetic equations contain the surface concentration of the electrochemically active complex, the current density must be normalized with respect to this value. The latter can be determined using the model of mass transfer of chemically interacting particles [1]. According to it, the total concentrations of the metal, ligand, or proton donors and acceptors obey laws of diffusion; hence, these quantities can be obtained using common procedures. Further, if the system is sufficiently labile, individual surface concentrations are available from the material balance equations with the analytical expressions of stability constants.
Analysis of the LPS voltammograms obtained for the Cu|Cu(II), glycine system is presented. NTPs, close to linear, were obtained for the charge transfer process Cu(II)L<sup>+</sup> + e = Cu(I)L. The following kinetic parameters were obtained at pH 4: the cathodic charge transfer coefficient α<sub>c</sub> = 0.44 and and the exchange current density <i>i</i><sub>01</sub> = 0.14 mA cm<sup>-2</sup>.
The method applied can be extended to other electrochemical systems where charge transfer is coupled with chemical steps. A similar analysis of hydrogen evolution on the copper electrode in acetate solutions has been carried out, yielding α<sub>c</sub> = 0.76 and <i>i</i><sub>0</sub> = 0.3 nA cm<sup>-2</sup>. Acetic acid acts as a labile proton donor in this case.