Non‐Random Island Nucleation in the Electrochemical Roughening on Pt(111)

Abstract

Many chemical surface systems develop ordered nano‐islands during repeated reaction and restoration. Platinum is used in electrochemical energy applications, like fuel cells and electrolysers, although it is scarce, expensive, and degrades. During oxidation‐reduction cycles, simulating device operation, nucleation and growth of nano‐islands occurs that eventually enhances the dissolution. Preventing nucleation would be the most effective solution. However, little is known about the atomic details of the nucleation; a process almost impossible to observe. Here, we analyze the nuclei‐distance distribution mapping out the underlying atomic mechanism: a rarely observed, non‐random nucleation takes place. Special, preferential nucleation sites that a priori do not exist, develop initially via a precursor and eventually form a semi‐ordered Pt‐oxide structure. This precursor mechanism seems to be general, possibly explaining also the nano‐island formation on other surfaces/reactions.