Temperature Reversible Synergistic Formation of Cerium Oxyhydride and Au Hydride: a combined XAS and XPDF study

In situ studies on the physical and chemical properties of Au in inverse ceria alumina supported catalysts have been conducted between 295 and 623 K using high energy resolved fluorescence detection X-ray absorption near edge spectroscopy and X-ray total scattering. Precise structural information is extracted on the metallic Au phase present in a 0.85 wt% Au containing inverse ceria alumina catalyst (ceria/Au/alumina). Herein evidence for the formation of an Au hydride species at elevated temperature is presented. Through modelling of total scattering data to extract the thermal properties of Au using Gruneisen theory of volumetric thermal expansion it proposed that the Au Hydride formation occurs synergistally with the formation of a cerium oxyhydride. The temperature reversible nature, whilst remaining in a reducing atmosphere, demonstatrates the activation of hydrogen without consumption of oxygen from the supporting ceria lattice.