H. Naohara et al., ELECTROCHEMICAL LAYER-BY-LAYER GROWTH OF PALLADIUM ON AN AU(111) ELECTRODE SURFACE - EVIDENCE FOR IMPORTANT ROLE OF ADSORBED PD COMPLEX, JOURNAL OF PHYSICAL CHEMISTRY B, 102(22), 1998, pp. 4366-4373
The adsorption and electrochemical reduction of the tetrachloropallada
te complex, PdCl42-, on on Au(lll) electrode in H2SO4 solution contain
ing PdCl42- was investigated using an electrochemical quartz crystal m
icrobalance (EQCM) and in situ electrochemical scanning tunneling micr
oscopy (STM). The adlayer of PdCl42- with at (root 7 x root 7)R19.1 de
grees structure on the Au(lll) substrate was observed by in situ STM m
easurement, and the amount of adsorbed PdCl42- determined by the EQCM
measurement was in good agreement with that estimated from this adlaye
r structure. In situ STM observation showed also that the electrochemi
cal deposition of palladium proceeded with an epitaxial layer-by-layer
growth mode and the PdCl42- complex adsorbed on the deposited palladi
um layer with the same adlayer structure. The adsorption of the PdCl42
- complex seemed to play an important role for the layer-by-layer grow
th of palladiurn in a large area, since it inhibits the vertical but f
actors the lateral growth of the palladium layer. The formation of the
Pd(111) bulk phase and the surface structure of Pd(lll) was confirmed
by X-ray diffraction (XRD) and the underpotential deposition of coppe
r, respectively.