Sj. Xia et Vi. Birss, A multi-technique study of compact and hydrous Au oxide growth in 0.1 M sulfuric acid solutions, J ELEC CHEM, 500(1-2), 2001, pp. 562-573
The growth and reduction of compact (alpha-) and overlying hydrous (beta-)
oxide films on polycrystalline Au electrodes in aqueous 0.1 M H2SO4 solutio
ns have been investigated using potentiostatic, cyclic voltammetry, ellipso
metric and quartz crystal microbalance (QCMB) techniques. All alpha -oxide
films, formed with time at constant potentials up to 2.6 V, or by multicycl
ing of the potential, are non-hydrated in nature, even when covered by a th
ick beta -oxide film. The alpha -oxide him composition is suggested to be A
uO below 1.5 V, and a mixture of AuO + Au2O3 at potentials above this, beco
ming predominantly Au2O3 at very high potentials. Up to three monolayers of
Au2O3 can be formed. When formed at constant potential, the beta -oxide fi
lm becomes increasingly hydrated as it thickens with time of growth, with a
mass to charge ratio and refractive index consistent with Au2O3.H2O and la
ter with Au2O3. 2H(2)O. In contrast, the beta -oxide film formed by multicy
cling has a higher mass overall, and becomes less hydrated as it thickens w
ith time, with a mass and refractive index consistent with Au2O3. 10H(2)O a
t short times, ranging to Au2O3. 2H(2)O as the film thickens. (C) 2001 Else
vier Science B.V. All rights reserved.