Effects of irreversibly adsorbed bismuth on hydrogen adsorption and evolution on Pt(111)

The behavior of the hydrogen evolution and adsorption reactions on Pt(111) electrodes modified by irreversibly adsorbed bismuth adatoms is reported in this paper. Whereas the inhibition of both H-upd and (bi)sulfate adsorption/desorption can be explained through geometric arguments for a rigid adlayer, it is necessary to invoke long-range effects in order to interpret the poisoning of the hydrogen evolution reaction, HER. Two statistical models are proposed intending to account for the inhibitory behavior of the HER. The first model (model A) is based on the existence of two types of sites on the modified substrate: active (normal) and completely deactivated, whereas the second model (model B) also considers infected sites, ie, partially active sites. Both models fit the experimental data for low bismuth coverages, but only model B fits the data in the whole range of adatom coverage. (C) 1997 Elsevier Science Ltd.