EQCM study of electrochemical modification of Bi2S3 films in the Zn2+-containing electrolyte

The electrochemical behavior of Bi2S3 as-deposited on Au using the successive ionic layer adsorption and reaction method has been investigated in the Zn2+-free background and Zn2+-containing electrolytes at different pH by electrochemical quartz crystal microbalance coupled with cyclic voltammetry and X-ray photoelectron spectroscopy. It has been shown that when the Bi2S3 film is reduced in the Zn2+-containing electrolyte Zn2+ ions are involved in electrochemical bismuth sulfide reduction and are partially reduced together with the bismuth sulfide film. The bismuth sulfide film initiates the adsorbed Zn2+ ions reduction prior to the traditional overpotential deposition of it. Reduction of Zn2+ ions prior to the overpotential deposition of Zn depends on solution pH: at pH 5 it occurs at more negative potential values and the observed mass changes due to Zn electrodeposition are greater than at solution pH 3. After bismuth sulfide film reduction in the Zn2+-containing electrolyte, Zn was detected as ZnO and metallic Zn at pH 5, while at pH 3 only ZnO was detected.