An investigation into the effect of ionic species on the deposition of tellurium and the formation of cadmium telluride

Abstract

The reduction of HTeO 2 + in the presence of various inorganic salts and ions has been studied at rotating glassy carbon and dropping mercury electrodes. The effect of added sodium salts (NaSO 4, NaCl, NaNO 3) was attributed to the anion present. SO 4 2− ions caused both a negative shift in the deposition potential and a decrease in the limiting current without changing the deposit morphology. Cl − ions caused a positive shift in the deposition potential, but no change in the limiting current, while NO 3 − had no effect n either current or potential. Neither Cl − nor NO 3 − caused changes in deposit morphology. The effect of SO 4 2− is xplained by complex or ion-pair formation between HTeO 2 + and SO 4 2−. Addition of a wide concentration range of CdSO 4 caused a decrease in the limiting current similar to that produced by SO 4 2− alone, but with no change in deposition potential. A dramatic change in deposit morphology from dendritic to smooth, due to CdTe formation, also accompanied CdSO 4 addition. However, deposit analysis revealed that conversion of Te to CdTe was incomplete at 298 K, even with a very large excess of Cd 2+ over HTeO 2 +.