VOLTAMMETRY, CHARGE DISPLACEMENT EXPERIMENTS, AND SCANNING-TUNNELING-MICROSCOPY OF THE PT(100)-BR SYSTEM

Stable, irreversibly adsorbed Pt(100)-Br adlayers composed of discharg ed bromine atoms can be formed through vapor or electrolyte dosage. Th ey survive emersion, can be studied in electrolytic media (either in t he presence or in the absence of bromide anions), and serve as scannin g tunneling microscopy samples. The voltammetric profile of Pt(LOO in acidic bromide solutions results from both hydrogen and bromide adsorp tion. Bromine coverages have be on measured from charge displacements under different experimental conditions, and they amount to 0.48-0.50 Br/Pt. The hydrogen adsorption contribution to the voltammetric charge in acidic bromide solutions, evaluated by charge displacement, corres ponds to hydrogen coverages around 0.90 H/Pt. An ordered Pt(100)-(3 x 4)-6Br (0.5 Br/Pt) adlayer structure has been imaged, resulting from t he coincidence of a distorted hexagonal Br layer (Br-Br distances betw een 0.38 and 0.42 nm) on the substrate net. However, for the most part of the surface it is difficult to find large, bidimensionally ordered domains. The temperature during bromine vapor dosage strongly affects the surface structure. Low temperature is required to minimize effect s on the structure of the Pt(100) substrate.