The Composition of the Second Coordination Sphere and Charge Transfer of the Nb(V)/Nb(IV) Redox Couple in Alkali Halide Melts
The standard rate constants for the Nb(V)/Nb(IV) redox couple were calculated based on cyclic voltammetry data and the Nicholson’s equation.
The following unusual series of the standard rate constants of charge transfer is experimentally determined in chloride-fluoride melts:
ks (KCl) < ks (CsCl) < ks (NaCl-KCl).
Ab initio calculations carried out by using PC Gamess/Firefly quantum chemical program showed that charge transfer activation energies can actually change in nonmonotonic manner in the series sodium-potassium-cesium, which leads to nonmonotonic change of the charge transfer rate constants in chloride-fluoride melts.
In pure fluoride melts, the following dependence of the standard rate constants was obtained using cyclic voltammetry:
ks (CsF) < ks (KF) < ks(NaF-KF).
It has been established that the standard rate constants of charge transfer increase with increasing temperature, as well as with replacement of the glassy carbon electrode with a platinum one.
The work was financially supported by the Russian Foundation for Basic Research (project 12-08-01178-а).