M. Weber et al., IN-SITU VIBRATIONAL SPECTROSCOPY ANALYSIS OF ADSORBED PHOSPHATE SPECIES ON GOLD SINGLE-CRYSTAL ELECTRODES, Colloids and surfaces. A, Physicochemical and engineering aspects, 134(1-2), 1998, pp. 103-111
The adsorption of phosphate species on Au(100) electrode at different
pHs is studied by using in situ Fourier Transform Infrared Spectroscop
y. The results are compared with those published previously for Au(lll
) and also for polycrystalline gold. H2PO4- ions present two spectral
features at 1000 and 1120cm(-1), consistent with a C-2v symmetry, as e
xpected. At pH 12.6 for the adsorption of PO(4)(3-)on Au(100) an abrup
t change in the band intensity is observed which is consistent with th
e lifting of the surface reconstruction. This change in the intensity
coincides with a current peak observed in the cyclic voltammogram and
has been related to the surface lifting of the reconstruction. The PO(
4)(3-)and H2PO4- ions when adsorbed on Au(100) show the same character
istic bands compared to Au(lll). The bands of the adsorbed species are
located at ca. 1120 cm(-1) and 1050 and 1085 cm(-1) for HPO42- and PO
43- respectively. At Au(100) surfaces the three-fold coordination for
both PO43- and HPO42- is very unlikely due to the mismatch between the
oxygen-oxygen distances and the atomic distances at the (100) surface
. For PO43-, where the bands for the solution and adsorbate phosphate
species do not overlap, it is possible to identify a consistent differ
ence in the band half-width, when compared with PO(4)(3-)adsorbed on A
u(lll). This difference in band width is tentatively assigned to a dif
ferent surface morphology of Au(100) after the lifting of the reconstr
uction. (C) 1998 Elsevier Science B.V.