IN-SITU AND REAL-TIME STUDY OF AN ELECTRODE PROCESS BY DIFFERENTIAL X-RAY-DIFFRACTION .1. AG UNDERPOTENTIAL DEPOSITION ON AU(111)

The underpotential deposition of Ag on Au(111) was used to demonstrate the adsorption of monolayers at the electrode\electrolyte interface a nd their measurement with X-ray diffraction in situ and in real time. The information obtained is that of the adlayer spacing during the mon olayer formation with respect to the interplanar spacing in the bulk o f the substrate. Although it was not straightforward to assign the spa cings of the Ag adlayer to adsorption sites on the Au(111) electrode, it was possible to observe phase transitions in the adlayer during und erpotential deposition. Detailed theory of the differential X-ray diff raction phenomenon and data analysis is given. A conventional laborato ry source of X-rays was used.