On the first step in zinc deposition - A case of nonlinear coupling with the solvent

P Quaino and E Colombo and F Juarez and E Santos and G Belletti and A Gross and W Schmickler, ELECTROCHEMISTRY COMMUNICATIONS, 122, 106876 (2021).

DOI: 10.1016/j.elecom.2020.106876

The deposition of zinc from aqueous solutions is of great practical importance, and it also serves as a prototype for the deposition of divalent ions. Both experiment and theory agree, that it takes place in two steps. Previous theoretical work 1 had suggested that the step, Zn++ +e(-) -> Zn+ takes place in the outer sphere, but gave a prohibitively high energy of activation of the order of 1.4 eV, in accord with the enigma of metal deposition postulated by Gileadi 2. In this work the treatment of the reactant - solvent interaction is substantially improved by introducing nonlinear terms based on molecular dynamics. Our calculations suggest that the first steps follows an inner sphere path with a much lower energy of activation, which results in a physically adsorbed Zn+ ion. The second step then occurs on the electrode surface. These findings are in line with experimental data.

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