Combined in situ XPS and in situ XAS study of Cu/ZnO catalysts for methanol steam reforming

Copper-Zinc oxide (alumina) catalysts are industrially relevant for a variety of processes (low temperature methanol synthesis, low temperature water-gas shift reaction, methanol steam reforming). We used high pressure X-ray photoemission spectroscopy (XPS) and high pressure soft X-ray absorption spectroscopy (XAS) for an extensive in situ study of Cu/Zn catalysts during the activation process in H2 and during the methanol steam reforming reaction. Analysis of XP core level spectra and the Cu L2,3 – and Zn L2,3 near edge X-ray absorption fine structure revealed detailed information about the catalyst surface under the presence of the reactive gas phase. We found that the reduction process (activation) plays a decisive role for the state of the catalysts under methanol steam reforming conditions. The Zn3p/Cu3p intensity ratio altered during the reduction process. A Zn species different to ZnO was found after calcination. Furthermore, a surface oxygen species (additional to ZnO) was observed after reduction and under reaction conditions. This investigation highlights the potential of surface sensitive in situ methods like high pressure XPS and soft XAS in general