Thermally-induced morphological transition in WOx deposited on a ZrO2(1 0 0) 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 WO_x 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.