ELECTROCHEMICAL BEHAVIOR OF TELLURIUM IN ACIDIC NITRATE SOLUTIONS

Electrochemistry of tellurium stationary electrode was studied in acidic nitrate solutions with pH 1.5 – 3.0. Cyclic voltammetry indicated that two products were formed at potentials above 300 mV (SCE): soluble HTeO 2 + (500 mV) and sparingly soluble H 2 TeO 3 (650 mV), but the former seemed to be an intermediate product for TeO 2 precipitation on the electrode surface. Formation of the solid products as porous layers was almost undisturbed and no electrode passivation was observed. H 2 TeO 3 and TeO 2 dissolved to HTeO 2 + under acidic electrolyte, but this process was hindered by pH increase. Cathodic polarization of tellurium electrode below -800 mV was accompanied by evolution of H 2 Te, which was then oxidized at the potentials approx. -700 mV. H 2 Te generated in the electrochemical reaction decomposed to elemental tellurium as black powdery precipitates in the bulk of the solution and a bright film drifting on the electrolyte surface.