A Comparative Study of Hydroxide Adsorption on the (111), (110), and (100) Faces of Silver with Cyclic Voltammetry, Ex Situ Electron Diffraction, and In Situ Second Harmonic Generation
Статья (Full article),
, E-ISSN: 1520-5827
Horswell Sarah L.
Pinheiro Alexei L. N.
Savinova Elena R.
Fritz-Haber-Institut der Max-Plank-Gesellschaf
Hydroxide adsorption on the (111), (110), and (100) faces of silver electrodes from mixed NaOH/NaF
solution is studied using cyclic voltammetry and in situ second harmonic generation (SHG). Cyclic
voltammograms for the three low index silver planes in alkaline electrolytes are for the first time compared.
They show two pairs of anodic and cathodic peaks in the potential interval below the equilibrium Ag/Ag2O
potential. These are attributed to the specific adsorption of hydroxide ions followed by submonolayer oxide
formation. The differences in the cyclic voltammograms for the (111), (110), and (100) planes are attributed
to different (i) work functions, (ii) surface atomic densities, and (iii) corrugation potentials for these surfaces.
Ex situ low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED)
show that disordered adlayers are formed on Ag(111) and Ag(100), in contrast to Ag(110), where ordered
structures are produced in the region of the first pair of current peaks. In the region of the second pair
of peaks, LEED indicates disordered oxide phases on each crystal plane and RHEED shows the presence
of small islands of c(2 × 2) structure at some potentials on (110) and (100). SHG measurements were
performed (i) in the potential scan mode at constant rotational angle and (ii) at constant potential as a
function of the rotational angle. The isotropic (for the (111), (110), and (100) planes) and anisotropic (for
the (110) and (111) planes) contributions to the SHG intensity were calculated by fitting the experimental
data and are discussed in terms of their dependence on the charge density at the interface, on hydroxide
adsorption, and on submonolayer oxide formation.