ON THE DETERMINATION OF ZERO CHARGE POTENTIALS OF PLATINUM GROUP-METALS IN THE PRESENCE OF FOREIGN METAL ADATOMS ON THE SURFACE

Some theoretical and experimental aspects of the potential of zero total charge (p.z.t.c.) determination of platinum group metals in the presence of foreign metal adatoms on the surface are discussed. A thermodynamic method for the determination of p.z.t.c. for electrodes of the platinum group metals in the presence of foreign metal adatoms on their surface has been proposed. It is shown that the hardness method can be used for studied of the effect of adatoms on the p.z.t.c. The possibilities of the thermodynamic and the hardness methods are compared in relation to the p.z.t.c determination. The estimation of the p.z.t.c. of electrodeposited Pt and Rh in the presence of differing amounts of adsorbed Ag was carried out by both methods. The values of p.z.t.c. determined both by the thermodynamic and by the hardness method are close. The p.z.t.c. of the studied electrodes shift in the negative direction in the presence of Ag adatoms. The possible causes of the observed shift are discussed.