INSITU ELECTROCHEMICAL SCANNING TUNNELING MICROSCOPY OF SINGLE-CRYSTAL SURFACES OF PT(111), RH(111), AND PD(111) IN AQUEOUS SULFURIC-ACID-SOLUTION

In situ electrochemical scanning tunneling microscopy (STM) was applied to single-crystal platinum(111), rhodium(111), and palladium(111) surfaces in an aqueous sulfuric acid solution. Atomically flat surfaces of Pt(111) are roughened in solutions by the electrochemical oxidation-reduction cycle. It is shown that a single potential cycle causes the formation of many adatoms and very small clusters on the Pt(111) terrace. A steady-state surface structure can be clearly observed after applying a few potential cycles. The STM image is composed of regularly arrayed islands whose diameter and height are in the ranges of 2-3 and 0.5-0.75 nm, respectively. Atomically flat terrace-step structures can be also observed on Rh(111) and Pd(111) surfaces. The effect of oxidation-reduction cycle on these surfaces is also discussed.