IN-SITU SCANNING-TUNNELING-MICROSCOPY OF WELL-ORDERED RH(111) ELECTRODES

A simple procedure is described for the preparation of an atomically flat surface of Rh(111) without the use of ultrahigh vacuum techniques or iodine protective adlayers, as described in previous literature. The well-defined Rh(111) electrode was characterized by cyclic voltammetry and in-situ scanning tunneling microscopy (STM). A highly reversible feature, the so-called ''butterfly'' peak, appeared at 0.64 V vs. RHE in the cyclic voltammogram in 0.1 M HClO4. An atomically flat terrace-step structure was consistently observed by STM on the well-ordered Rh(111) surface. Atomic images of a Rh(111)-(1 x 1) structure were found at potentials positive end of the butterfly peak and in the hydrogen adsorption region. Dipping the Rh(lll) electrode into a 1 mM iodine solution resulted in the formation of a Rh(111)(root 3 x root 3)R30 degrees-I overlayer. The electrochemical activation of the Rh(111) surface by potential cycling is also described.