Intervalence Charge Transfer of the Nb(V)/Nb(IV) Redox Couple in Alkali Chloride Melts: Experiment and Quantum-Chemical Calculations

Abstract

The standard rate constants of charge transfer (k s) for the Nb(V)/Nb(IV) redox couple in KCl-NbCl5 and CsCl-NbCl5 chloride melts are determined. The Nb(V) electrochemical reduction process in the NaCl-KCl-NbCl5 melt was shown being reversible; hence, the determination of k s appeared impossible. Values of k s in the KCl-NbCl5 melt are higher than those in the CsCl-NbCl5 one. Previously, in a quantum-chemical calculations of nM+·[NbCl6] model systems (M = Na, K, Cs), containing a complex anion with cations outer-sphere (OS) shell (nM+) have been done. It was found that compositions with an intermediate number of OS cations n < n lim, where n lim is the limiting number of OS cations bound to a given complex, are thermodynamically most stable. The aim of this quantum-chemical study is an estimation of the temperature effect on the composition of the stable particles in the extended systems M+∙[NbCl6]+18MCl (M = Na, K, Cs).

Electrochemical Behavior of the SmF3 in Alkali Chloride Melts

“…The diffusion coefficients decrease with a change of the composition of the second coordination sphere from sodium to cesium. Similar dependencies for D values are well known (9,10). It is associated with a decrease of the counter-polarizing effect during the transition from Na to Cs in second coordination sphere of the samarium complexes, which in turn causes a decrease of the metalligand bond length and increase the samarium complexes stability.…”

Electrochemical Behavior of SmF3 in Alkali Chloride Melts

“…[62][63][64] Quantum-chemical calculations for explanation of this phenomenon are needed. 58,59,65 Conclusions Electrochemical behavior of the Sm(III)/Sm(II) redox couple was studied in NaCl-KCl-SmF 3 , KCl-SmF 3 and CsCl-SmF 3 melts by cyclic voltammetry. It was found that the redox process was reversible in NaCl-KCl-SmF 3 , KCl-SmF 3 and CsCl-SmF 3 up to the scan rate 1.0 V s −1 .…”

(Digital Presentation) Study of the Intervalence Charge Transfer in a 18NaCl+Na3SmF6 Model System By Quantum Chemical Methods

“…A number of papers have investigated the effect of the electrode surface on electrochemical electron transfer by quantum-chemical methods (4,8,11,19). Quantumchemical studies of electron transfer in various melts are presented in (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).…”