UNDERPOTENTIAL DEPOSITION OF CU ON PT(001) - INTERFACE STRUCTURE AND THE INFLUENCE OF ADSORBED BROMIDE

Using in situ x-ray diffraction, we studied the underpotential deposit ion (UPD) of copper onto a Pt(001) electrode both in pure perchloric a cid and in the presence of bromide anions. In pure perchloric acid, th e Cu is deposited in pseudomorphic p(1x1) islands. In the presence of bromide anions, the strong Pt-Br interaction significantly broadens th e potential range of Cu UPD. We propose that Pr remains in the interfa ce region throughout the UPD process, at first in a disordered Cu-Br p hase and then, at more negative potential, forming a c(2x2) closed-pac ked monolayer on top of the completed p(1X1) Cu monolayer. The structu res are compared to those found during Cu UPD onto Pt(111), and explai ned in terms of the metal-halide interactions and the Pt surface atomi c geometry.