In situ monitoring of electrochemically induced roughening with the crystal truncation rod technique

We have employed the crystal truncation rod technique to monitor (in situ) the electrochemically induced roughening of a Pt(111) electrode pretreated with a chemisorbed layer of iodine. We find that for the electrode as prepared (both in air and in contact with an electrolyte solution at the rest potential) the surface is best described by one that has an rms roughness of 3.30 {plus_minus} 0.3 {angstrom} and where the atoms that are displaced from a perfectly truncated lattice still occupy lattice positions. Reductive desorption of the iodine adlayer at {minus}0.90 V does not alter the interfacial roughness. However, the application of a potential of +1.0 V for 15 min results on a significantly rougher interface. In this case the roughness due to displaced atoms occupying lattice positions is 3.35 {plus_minus} 0.34 {angstrom}, and there is also a second contribution to the roughness that can be described in terms of a Debye-Walker factor and which contributes an additional roughness of 2.05 {plus_minus} 0.25 {angstrom}. 19 refs., 4 figs.