The electrodeposition of CdS was conducted in aqueous solution containing CdSO4 and Na2S2O3 as sources supplying cadmium and sulfur, respectively. The roles of several additives, comprising (NH4)2SO4, NaCl and glycerol were investigated by cyclic voltammetry. The proposed mechanism of the electrodeposition of CdS consists of an adsorption process coupled with a chemical reaction: Cd2+ + S2- → CdS and/or an adsorption process coupled with an electron transfer reaction: Cd2+ + S + 2e- → CdS. The presence of all such additives enables the adsorption processes and the electron transfer reaction to take place at the potentials positive of - 0.8 V, thereby promoting the formation of CdS; in addition, the undesired electrodeposition of Cd was suppressed.
