ATOMIC-STRUCTURE OF CLEAN AND CU COVERED PT(110) ELECTRODES

The structure of Pt(110) electrodes in pure and Cu2+ containing H2SO4 solution and Cu underpotential deposition (UPD) on that surface were investigated by in-situ scanning tunneling microscopy. The surface topography indicates that the (1 X 2) missing row reconstruction was formed during flame annealing but lifted during cool down or during immersion of the sample into the electrolyte at the open cell potential. During Cu deposition on that surface a (1 x 1) structure is observed in the entire UPD potential range. This is explained in a model where Cu deposition proceeds via adsorption of highly mobile, repulsively interacting Cu adatoms, forming a dilute, mobile adlayer, until at higher coverages a (1 X 1) adlayer structure results. The differences between these results and those of previous ex-situ studies regarding the stability of the reconstruction and the structure of the Cu adlayer are discussed.