Adlayer of Hydroquinone on Rh(111) in Solution and in Vacuum Studied by STM and LEED

Hydroquinone (HQ) adlayers were formed on Rh(111) in HF solution and in vacuum. Cyclic voltammetry showed that HQ adsorbed on Rh(111) does not undergo redox reactions on the surface. In situ scanning tunneling microscopy revealed that HQ formed a (root 7X root 7)R19.1 deg structure on Rh(111). A strong interaction was seen between two adjacent hydroxyl groups of neighboring HQ molecules. After the sample was transferred into vacuum, low-energy electron diffraction measurement was performed, which showed that the (root 7 X root 7)R19.10 structure of the HQ adlayer remained unchanged even in vacuum. The HQ adlayer formed on Rh(111) by vapor deposition was found to have the same structure as that observed in solution. Interestingly, the adlayer structure of HQ on Rh(111) was almost identical to that previously reported on Pt(111), (2.56 X 2.56)P16DG, despite the difference in the lattice constants of those metal surfaces.