BROMINE ADSORPTION ON PT(111), PT(100), AND PT(110) - AN STM STUDY INAIR AND IN ELECTROLYTE

Bromine adlayers formed by flame annealing of platinum single crystal surfaces and quenching in bromine vapor were studied by STM and cyclov oltammetry. Bromine forms protective layers which, similar to iodine, prevent contamination of the surface and lead to well-defined surfaces . On Pt(111) a (4 X 4) structure is observed, on Pt(100) a disordered structure, both of which are compatible with densely packed adlayers o f bromine. On the Pt(110) surface a complex structure is observed whic h is similar to that formed by iodine on Pt(110). The reconstructions of Pt(100) and (110) are lifted. Cyclovoltammetric peaks can be attrib uted to concomitant hydrogen adsorption and bromine desorption; the cy clovoltammograms in bromide electrolyte for clean and for bromine-quen ched Pt(111) are identical.