Me. Martins et al., DYNAMICS OF SURFACE ALLOYING PROMOTED BY CADMIUM UNDERPOTENTIAL DEPOSITION ANODIC-STRIPPING CYCLES ON IRREGULAR SILVER ELECTRODEPOSITS, Journal of electroanalytical chemistry [1992], 375(1-2), 1994, pp. 141-155
The underpotential deposition of Cd from dilute aqueous 5 x 10(-3) M C
dSO4 + 0.5 M Na2SO4 + 0.01 M H2SO4 on Ag electrode-posits grown on pol
yfaceted Pt single-crystal microspheres was studied using potentiodyna
mic and potentiostatic techniques, transmission electron diffraction,
scanning tunneling microscopy and X-ray photoelectron spectroscopy. Ag
electrodeposits were grown in 5 x 10(-3) M Ag2SO4 + 0.5 M Na2SO4 + 0.
01 M H2SO4 at cathodic overpotentials eta(c) of -0.06 V and -0.58 V to
form a columnar and dendritic Ag surface respectively. Surface rearra
ngement processes involving the formation of Cd + Ag alloys were studi
ed by stripping voltammetry after the potential was held for a certain
time at different preset values covering the potential range in which
the degree of surface coverage by Cd atoms was less than or close to
unity (theta(c) less-than-or-equal-to 1) on both Ag surfaces. Surface
diffusion and penetration of Cd atoms into bulk Ag for theta(c) less-t
han-or-equal-to 1 are discussed. A place-exchange mechanism is advance
d to account for the kinetics of Cd + Ag alloy formation.