The influence of Cu adatoms on the Zn upd on polycrystalline thin gold film electrodes: a study using surface conductance measurements

The adsorption behaviour of Zn upd and irreversibly adsorbed Cu on thin gold films in a NaH2PO4 electrolyte was studied applying both CV and surface conductance (SC) measurements. These processes were studied separately and the upd of Zn in the presence of previously adsorbed Cu was also studied. Zn upd and ups occur with an apparent number of transferred electrons n=1. The SC measurements show that Zn upd does not conform the surface Linde rule. The n value obtained can be explained by considering that the product is not Zn(0). The SC response of Cu irreversibly adsorbed on gold shows an increase in SC as the degree of coverage increases. ltammetric response for the upd of Zn on Cu-covered gold electrodes shows that a Cu coverage around θCu∼0.66 is enough to inhibit the Zn upd process on gold completely. The charge relation (QCu vs. QZn) shows that one Cu adatom blocks one Zn site. The SC shows that the response of Zn on Cu pre-adsorbed on gold is additive. This last behaviour can be explained only by inferring a phase segregation in two dimensions where Cu and Zn depositions occur in the form of individual islands.