Abstract
The behavior of CdTe in deposition and dissolution in a basic ammoniacal aqueous media (pH 10.7) containing Cd(II) and Te(IV) species was investigated in situ using an electrochemical quartz crystal microbalance (QCM). The instantaneous current efficiency of CdTe deposition during potentiostatic cathodic electrolysis, under dark conditions, increased up to 80-90% at the beginning of the electrolysis, but later gradually decreased to ca. 60%, resulting in an overall efficiency of around 70%. In contrast, the overall current efficiency under illumination with visible light increased steeply to 100%. Two anodic waves appeared during the positive-going scan of a cyclic voltammogram in the CdTe deposition bath, and were assigned to (i) a two-electron decomposition of CdTe into Cd(II) ions and elemental Te followed by (ii) a four-electron dissolution of the resulting Te into Te(IV) ions. These observed phenomena are discussed using a potential-pH diagram devised for the system.
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