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

A simple procedure is described for the preparation of an atomically f lat surface of Rh(111) without the use of ultrahigh vacuum techniques or iodine protective adlayers, as described in previous literature. Th e well-defined Rh(111) electrode was characterized by cyclic voltammet ry and in-situ scanning tunneling microscopy (STM). A highly reversibl e feature, the so-called ''butterfly'' peak, appeared at 0.64 V vs. RH E in the cyclic voltammogram in 0.1 M HClO4. An atomically flat terrac e-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 fou nd at potentials positive end of the butterfly peak and in the hydroge n 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 de grees-I overlayer. The electrochemical activation of the Rh(111) surfa ce by potential cycling is also described.