Correlation between the electrochemical properties of colloidal oxides and supported oxides on metallic substrates.

M.J. AVENA; R.A. CABROL; O.R. CÁMARA; C.P. DE PAULI

JOURNAL OF APPLIED ELECTROCHEMISTRY

SPRINGER

Lugar: Berlin; Año: 1992 vol. 22 p. 959 - 965

0021-891X

Mixed oxide electrodes of Ti(IV) and Cr(III) were prepared by calcining Cr(OH)3 layers deposited on metallic titanium supports. This treatment produced a mixed oxide film of TiO2-Cr 2 03 covered with a layer o f pure Cr2 03. The electrochemical response (cyclic voltammetry) shows the presence of two or three oxidation peaks depending on the electrode preparation conditions. One peak may be interpreted as the oxidation of Cr(III) to Cr(VI) species and the appearance of other peaks is due to the presence of chromium atoms in oxidation states higher than (III). The results of chemical analyses, electrophoretic mobilities and acid-base potentiometric titrations on calcined Cr(OH)3 powders shows that the calcination step in air produced the decomposition of the Cr(III) hydroxide to the Cr(VI) oxide. Soluble Cr(VI) compounds were found in equilibrium with the suspended powder oxide which markedly affected the shape of the titrations curves. F r o m the amount of Cr(VI) present in solution it was possible to correct the experimental ao-pH curves. These corrected data indicated that Cr(VI) soluble species adsorbed at the Cr203/electrolyte interface.