Electrochemical properties of palladium adlayers on Pt(110) substrates

Palladium deposition on Pt(1 1 0) electrodes was studied. Differently from Pt(1 1 1) and Pt(1 0 0), first and further layers cannot be distinguished in this case only through the voltammetric behavior of hydrogen and anion adsorption. The potential of zero total charge (pztc) was determined as a function of the amount of deposited Pd using CO charge displacement experiments and voltammetric curves. The variation of the voltammetric charge due to hydrogen and anion adsorption has been followed during Pd deposition. The voltammetric charge between 0.06 and 0.4 V first decreases to a minimum, then increases and finally becomes stable, suggesting that the surface is finally covered with a Pd multilayer. The pztc and CO oxidation charge show similar behavior. CO oxidation, NO reduction and Cu UPD were used as probes to monitor Pd coverage. The potential of CO oxidation increases with Pd coverage while the potential of NO reduction decreases. Using the information obtained from Cu UDP and FTIR experiments it has been possible to determine when the first Pd single layer was completed and when a second (further) layer(s) starts to grow.