AN EXPERIMENTAL CORRELATION BETWEEN POINTS OF ZERO CHARGE AND X-RAY PHOTOELECTRON-SPECTROSCOPY CHEMICAL-SHIFTS OF OXIDES

Measurements are reported of X-ray photoelectron spectroscopy (XPS) in vestigations, performed under conditions of ultrahigh vacuum, of sever al metal oxides either produced commercially (high purity) or prepared in the laboratory. The same oxides were also subjected to electrochem ical measurements in aqueous solutions for the determination of the po int of zero charge (PZC) values and/or the isoelectric points (IEPs). The PZC (IEP) values appear to be linearly correlated with the sum of the metal and oxygen XPS chemical shifts (DM + DO). The higher (more a lkaline) the PZC (IEP), the lower the XPS (DM + DO) term and vice vers a. The weighting of the different components in the accuracy of the co rrelation is discussed. It is shown how a cross comparison between exp erimental XPS and electrochemical data obtained for the same samples c an be used as a diagnostic criterion for the occurrence of secondary p henomena at the solid/liquid boundary.