Thermally-induced morphological transition in WOx deposited on a ZrO2(100) substrate

A combined atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) study of tungsten oxide model catalysts is presented. The model catalysts were prepared by applying the real preparation method to a ZrO2(1 0 0) single crystal support. AFM imaged several granular structures of scattered dimensions on the surface of ZrO2(1 0 0) in the as prepared samples. After heating, at low loading the tungsten species rearranged into small WOx particles strongly interacting with the substrate. At high tungsten content large WO3 aggregates also formed. XPS analysis confirmed these changes. The estimated surface density of the interacting W-containing species closely matched that of real catalysts.