A COMPREHENSIVE STUDY OF BISULFATE ADSORPTION ON PT(111) BY RADIOACTIVE LABELING AND VOLTAMMETRY

Adsorption of bisulfate anions on single crystal Pt(111) electrode, ordered and disordered and on polycrystalline platinum has been studied by the use of radioactive labeling method and cyclic voltammetry. The studies have revealed that the saturation surface concentration of bisulfates is 20% higher on the ordered Pt(111) surface than on the polycrystalline electrode. The increased adsorption may most likely be due to a favorable spatial configuration of the anions and surface water molecule networks at the single crystal interface. A consistent model of adsorption on the ordered surface emerges if one assumes that a form of hydrogen exists that is stable at relatively positive electrode potentials, adsorption of which is modified by coadsorbed (bi)sulfate. Available, although not yet direct, evidence is presented which shows that this form of hydrogen is a subsurface hydrogen. The significance of surface geometry and stability in the anomalous voltammetric behavior is discussed vs. that of the long range order effects on the solution side of the Pt(111) solid-liquid interface.