CONTRASTING ELECTROCHEMICAL-BEHAVIOR OF IRREVERSIBLY ADSORBED SB MONOLAYER ON PT(100) AND PT(111) SINGLE-CRYSTAL ELECTRODE SURFACES

We report contrasting electrochemical behavior of irreversibly adsorbe d Sb on Pt(100) and Pt(111) single crystal electrodes. The irreversibl y adsorbed Sb on both Pt(100) and Pt(111) surfaces showed redox featur es. The saturation charge of the irreversibly adsorbed Sb on Pt(100) w as 206 +/- 3.1 mu C cm(-2) (theta = 0.33) in 0.05 M H2SO4 solution. In the Sb2O3-saturated solution, the charge of Sb on Pt(100) was increas ed to be 244 +/- 8.8 mu C cm-2 (theta = 0.39), which means that additi onal Sb is underpotentially deposited during the reduction of the irre versibly adsorbed oxygenous Sb. On Pt(111), on the other hand, the sat uration charge of the irreversibly adsorbed Sb was observed to be 275 +/- 8.7 mu C cm-2 (theta = 0.38) and the charges associated with the r edox feature of the irreversible Sb adsorbate decreased during cyclic voltammetric scans, depending on the Sb concentration of the contactin g solution. This particular behavior of Sb on Pt(111) is interpreted i n terms of the formation of an electrochemically inactive Sb species. (C) 1998 Elsevier Science S.A. All rights reserved.