D. A. Vetrova, S. A. Kuznetsov.
ABSTRACT
The redox reaction Ti(IV) + e– ↔ Ti(III) in CsCl-CsF(10 wt %)-K2TiF6-based melts with additions of alkaline earth metal cations (Mg2+, Ca2+, Sr2+ and Ba2+) was studied by cyclic voltammetry method. The quasi-reversibility region of titanium complexes for recharge process has been determined and the standard rate constants of charge transfer for the redox couple Ti(IV)/Ti(III) in CsCl-CsF(10 wt %)-K2TiF6-based melts with additives of alkaline earth metal cations were calculated. The standard rate constants of charge transfer do not depend on the polarization rate and increase with temperature increasing. It is shown that the standard rate constants of charge transfer increase with increasing mole ratio of alkaline earth metal cations to titanium up to a certain Me2+/Ti(IV) ratio and then decrease with further increasing of Me2+ cations concentration in the melt. It was found that the rate constants of charge transfer increase with increasing ionic potential of the addition, reaching a maximum value for complexes with outer-sphere cations of magnesium, and this dependence is rectilinear. The activation energies of the charge transfer process in melts with additions of alkaline earth metal cations were calculated. The values obtained are significantly lower than the activation energies of the initial system CsCl-CsF(10 wt %)-K2TiF6. It is shown that the standard rate constants of charge transfer decrease and the activation energy values increase in transition from (NaCl-KCl)equimol. based melt to KCl-KF and CsCl-CsF melts both without addition and with addition of alkaline earth metal cations.
KEYWORDS
melt, cyclic voltammetry, titanium complexes, redox couple, quasi-reversible process, standard rate constants of charge transfer.
DOI: 10.31857/S0235010622060135