| Electrochemical reactions in 10m/o NaVO(,3)-Na(,2)SO(,4) solutions at 900 C have been studied using cyclic voltammetry, chronopotentiometry, chronoamperometry and dynamic polarization. Vanadate ions, VO(,3)('-), are the electroactive species in these solutions in the basicity range from -9.7 to -13.85 on the log aNa(,2)O scale. VO(,3)('-) ions undergo a one-electron reversible redox reaction and the product of the reduction reaction is consumed by an irreversible succeeding chemical reaction. AC impedance measurements indicate that diffusion of the reactants to the working electrode surface controls the electrochemical process at the working electrode/solution interface. The Helmholtz-Stern model for the structure of the double layer does not apply to 10m/o NaVO(,3)-Na(,2)SO(,4) and pure Na(,2)SO(,4) solutions at 900 C. Na(,2)SO(,4) is a suitable supporting electrolyte in the study of the electrochemical reactions by vanadate solutes provided that the cathodic switching potential is limited to -1450 mV relative to the Ag/Ag('+)/mullite high temperature reference electrode. |
