Potentials of zero charge and capacitance minima of polycrystalline gold in sodium fluoride solutions

The potential of zero charge ( pzc) of polycrystalline gold in sodium fluoride solutions was determined using the piezoelectric technique and compared with the potential of the capacitance minimum. E c, measured simultaneously. In general the two do not coincide which is in keeping with the surface heterogeneity model of polycrystalline metals. A series of oxidation/reduction cycles causes the pzc to shift negatively and eventually become coincident with E c. This is interpreted as due to the roughening of the surface. The results show no evidence of the specific adsorption of fluoride ions. An improved cell for the piezoelectric method is described.