On the global and local values of the potential of zero total charge at well-defined platinum surfaces: stepped and adatom modified surfaces

Abstract

N 2O reduction and CO charge displacement measurements have been used to elucidate the overall and local values of the potential of zero total charge (pztc) for a series of well-defined clean and bimetallic platinum electrodes. It is demonstrated that in all cases, analyses which incorporate measurements of surface charge (cyclic voltammetry) together with local values of the pztc (nitrous oxide reduction) to evaluate overall total charge may provide excellent agreement with overall pztc data determined using CO charge displacement. This illustrates both the veracity and consistency of both methods of pztc determination. The previous analysis reported in [J. Electroanal. Chem. 532 (2002) 67] on stepped surfaces in the [1 1 ̄ 0] zone are here extended to stepped surfaces in the [0 1 1 ̄ ] zone, vicinal to the {1 0 0} plane. In contrast to the earlier study it is shown that the local pztc of step and terrace sites is independent of step density. For Bi adsorbed in step sites on Pt{3 3 2}, a shift to more positive values of the overall pztc relative to the clean surface is observed in agreement with predictions based on an earlier study [Electrochem. Commun. 3 (2001) 590]. The reason for this shift is discussed. Finally, the local pztc of Pd islands on Pt{1 0 0} is determined and used to calculate the variation in pztc as a function of Pd coverage. Again, good agreement with the pztc values extracted from CO displacement data is obtained.