SURFACE CHARACTERIZATION OF Cux/2Cd1-xIn2+x/2S4 MODEL CATALYST

The sulphospinels reported in the title, with x ranging from 0 to 1.0, were characterized by bulk and surface techniques (XRD, megnetic susceptibility, reflectance specfioscopy and XPS, including x-ray induced Auger spectroscopy). Homogeneou spinel solid solutions are formed up to x = 0.4 whereas for the other compoeitions the CuInS2 phase also was identified by XRD. Only monovalent copper was found in all the samples in the bulk as well as on the surface. The surface of the sulphospinels is stable to air; on the contrary the surface of CuS is trnasformed to Cu2SO4. Making use of the Wagner Auger parameter and of a simple approximation of the shifts observed in the core electron binding energieg we estimate the charge distribution and the electronic environrent of the indium ions in the different sites of the spinel structure.