Influence of supported gold on the dynamics of reduction and crystallization of iron oxides: A dispersive X-ray absorption near edge structure spectroscopy and X-ray diffraction study Article uri icon

abstract

  • Iron oxide-supported gold samples were charac-terized by X-ray absorption near edge structure (XANES) spectroscopy during treatments in flowing H 2 at increasing temperature. Spectra were recorded at the Au L III and Fe K edges to monitor the reduction of both metals and to determine the influence of gold on the reducibility of the support. The results show that reduction of Fe3%2b to Fe2%2b on the support occurs at lower temperatures in samples containing gold than on samples of the bare support, with the reduction temperature being dependent on the gold content. X-ray diffraction patterns characterizing samples after H2 treatments at various temperatures complement the XANES data and indicate that the presence of gold favors the crystallization of the support to give Fe 3O4. Our data emphasize the power of XANES spectroscopy in following changes in the oxidation states of both gold and iron and suggest that the role that gold might have in promoting the reduction and crystallization of iron oxide support is to provide sites for hydrogen dissociation. Hydrogen moieties might spillover from the gold nanoparticles to the support, promoting its reduction and ensuing structural changes. © 2011 American Chemical Society.

publication date

  • 2011-01-01