Atom-resolved EC-STM studies of anion adsorption at well-defined surfaces:Pd(111) in sulfuric acid solution

The interfacial structure of well-defined Pd(lll) single-crystal electrodes in 0.05 M H2SO4 has been studied by electrochemical scanning tunneling mic roscopy (EC-STM) at potentials within the electrical double-layer region. E xperiments with (virtually) atomically sharp STM tips yielded images of suc h quality that the intermolecular and intramolecular structures of the high ly ordered compact layer could actually be resolved on an atomic scale. Fun damental concepts in inorganic chemistry have been invoked to postulate tha t SO42-, H3O+, and H2O are the most likely constituents of the compact laye r. A structural model of such a compact layer is presented. (C) 2000 Academ ic Press.