NEWS: Nature Materials...click here for a movie!
Platinum plays a central role in a variety of electrochemical devices. One of the challenges to make practical applications economically feasible is the prevention of the electrode degradation, especially under oxidizing conditions. Although it is known that the surface of a Pt electrode can be changed irreversibly upon repeated oxidation and reduction, the underlying atomic processes are far from understood.
Here we show that the evolution of the electrochemical signal of Pt(111) is directly correlated to the roughening of the platinum surface. This quantitative analysis was made possible by simultaneously performing cyclic voltammetry and in situ electrochemical scanning tunneling microscopy (EC-STM) experiments.
We find that the growth of the formed Pt nanoislands continues on very long timescales up to at least 170 cycles. We identify two regimes in this roughening process: (i) a "nucleation& early growth" regime of nanoisland formation and some minor, most dominantly lateral growth, and (ii) a "late growth" regime upon prolonged cycling, in which the nanoislands grow in height after their coalescence.
In the "late growth" regime the strong correlation between the electrochemical and STM data suggests a linear relationship between the number of created surface sites and the total surface roughness. Each created step contributes equally to the electrochemical as well as to the roughness evolution. In contrast, in the "nucleation & early growth" regime, created step sites contribute to the roughness, but not to the electrochemical signal.
These results present an important step forward in understanding the atomic scale process of the electrochemical roughening of Pt(111).

We are currently working on an analysis of our data that will provide detailed atomic information of the formed nano-islands. Correlating the variation of the various, identified surface sites (different types of steps, kinks, and corner sites) with the variation of the peaks that appear in the CV, will (hopefully) disentangle the individual contributions. This would be a major step forward in the understanding of the catalytic reactivity of Pt(111).

Publications (click the link):
2) Correlation of surface site formation to nanoisland growth in the electrochemical roughening of Pt(111)
1) Design of a high-speed electrochemical scanning tunneling microscope