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Journal of Applied Electrochemistry, Vol.50, No.2, 149-158, 2020
Kinetics of active zinc dissolution in concentrated KOH solutions
The kinetics of zinc dissolution in concentrated potassium hydroxide solution were determined as a function of KOH concentration, amount of added ZnO, and temperature through linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The measurements were evaluated with a simplified reaction scheme in which an intermediate Zn-I species is formed on the electrode surface that subsequently reacts to a soluble Zn-II species. Analysis of the LSV data with a two-step Butler-Volmer kinetics showed that the transfer coefficients and the surface coverage of the intermediate are approximately constant in the entire range of operation conditions, whereas the exchange current density for the first reaction step is about five times larger than for the second step. Analysis of the dynamic EIS measurements resulted in very similar current densities than obtained from the quasi-stationary LSV method. For the first time, activation energies describing the temperature dependence of the exchange current density were also determined. Graphic abstract