Abstract
The distribution of the adsorbed CO species produced by formic acid chemisorption on a smooth rhodium electrode in acid medium has been investigated using infrared reflectance spectroscopy. When the adsorption takes place at a potential of 0.2 V vs. RHE, from a 0.25 M HClO 4 + 0.1 M HCOOH solution, the surface is found to be covered by ca. 53% of linearly bonded CO L, ca. 42% of twofold bridge-bonded CO B and ca. 5% of multi-fold bridge-bonded CO m species. These figures depend on the concentration of HCOOH in the bulk. When Pb atoms are adsorbed progressively on the rhodium surface, a one by one replacement of the CO B species by Pb adatoms is observed, suggesting that lead adatoms occupy 2 adjacent sites. It is concluded that the CO ads layer formed on a rhodium surface, due to different structures of the adsorbed species, can be used as a probe for determining the number of sites necessary for the adsorption of a given adatom.
Published Version
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