Electrodeposition of CdS from acidic aqueous thiosulfate solution—Invesitigation of the mechanism by electrochemical quartz microbalance technique

Electrochemical quartz crystal microbalance was used to study mechanism of cathodic electrodeposition of CdS from acidic aqueous solutions containing 0.01 M Cd(ClO4)2 and 0.1 M Na2S2O3 as a source of sulfur. Experiments were performed by means of cyclic voltammetry and potentiostatic method. A comparison of gravimetric and current responses at pH 3 and 4 allowed for determination of the potential range in which side reactions of reduction of SO32− and H+ ions compete most strongly with formation of CdS. The film thickness was determined by means of two methods: from AFM profiles and EQCM measurements.

► Cathodic electrodeposition of CdS from acidic thiosulfate solution occurs via EC mechanism. ► H2S formed by electrochemical reduction of colloidal sulfur reacts with Cd2+ ion. ► The same mechanism is observed at pH 3 and 4. ► Relationship between deposition charge and film thickness was determined from EQCM and AFM experiments.