INFLUENCE OF LEAD AND THALLIUM UNDERPOTENTIAL ADSORBATES AT SILVER SINGLE-CRYSTAL SURFACES ON DIFFERENT REDOX REACTIONS

The influence of underpotential Pb- and Tl-adsorbates at rotating disc silver single crystal surfaces (111), (100), and (110) on the kinetics of 'outer-sphere' and 'inner-sphere' redox reactions was studied in 0.5 M NaClO4 and 0.5 M Na2SO4 solutions (2 < pH < 4) containing Fe3+, Ce4+ or NO3- ions. While the reduction of Fe3+ and Ce4+ under limiting diffusion conditions was not affected by the metal adsorbates, a strong inhibition effect correlated to the degree of Pb- or Tl-adsorbate coverages was observed in the case of the reduction process in the presence of NO3- ions. The results are interpreted in terms of a strong chemical interaction between the reactant or a reaction intermediate and the silver substrate, taking into account the previously proposed superlattice structures of the metal adsorbates, depending on the orientation of the silver single crystal surfaces and on the underpotential range. © 1979 Chapman and Hall Ltd.