Voltammetric measurements on MexOy (Me = Bi, Cu, V) compounds and comparison with results for BICUVOX.10

Voltammetric measurements on cells of arrangement Pt,Ar\sample\YSZ\Ar,Pt wi th a very small sample mass ('microsamples') turned out to be a very conven ient tool for the determination of thermodynamic properties of oxides. Meas urements were made on Bi2O3, CuO and V2O5 microsamples and on nickel and co pper metal between 550 and 700 degrees C. The measurements on nickel were u sed for the calibration of the reference electrode. The measurements on CuO showed the advantage of the use of microsamples. Comparison of the results for CuO with the standard potential, calculated from thermodynamic data in the literature, revealed the high accuracy of the method. In the case of m easurements on V2O5 a possible reaction path was identified. The vanadium s ystem is very complicated because of the large number of stable oxidation s tates for vanadium in VxOy compounds. The measurements on Bi2O3 showed a la rge deviation of about 100-150 mV from the calculated equilibrium potential s. BICUVOX.10 microsamples are reduced irreversibly below -570 mV against a reversible oxygen electrode in 1 atm O-2 at 600 degrees C in the first neg ative sweep. The voltammograms for BICUVOX.10 are compared with measurement s on pure MexOy compounds and with calculated data. (C) 1999 Elsevier Scien ce B.V. All rights reserved.