Surface characterization of Cux/2Cd1−xIn2+x/2S4 model catalysts

The sulphospinels reported in the title, with x ranging from 0 to 1.0, were characterized by bulk and surface techniques (XRD, magnetic susceptibility, reflectance spectroscopy and XPS, including x-ray induced Auger spectroscopy). Homogeneous spinel solid solutions are formed up to x = 0.4, whereas for the other compositions 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 transformed to Cu2SO4. Making use of the Wagner Auger parameter and of a simple approximation of the shifts observed in the core electron binding energies, we estimate the charge distribution and the electronic environment of the indium ions in the different sites of the spinel structure.