“…When the bismuth sulfide film is reduced in the Zn 2+ -free background electrolyte, both at solution pH 3 and 5, the film mass under the potential region of negative current peak C1 decreases (df/dt and Df values increase). From our previous XPS analysis data [25], it was concluded that the bismuth sulfide film is reduced to Bi 0 and the decrease in the film mass under the potential region of cathodic peak C1 detected by EQCM is attributed to the detachment of S 2À ions from the electrode surface.…”