XAS study on microstructure of Au nanoparticles deposited onto alumina

X-ray adsorption spectroscopy (XAS) was applied to the characterization of the Au/δ-Al2O3 catalysts with different mean Au particle sizes (〈dl〉=2–28 nm) prepared by adsorption of anionic Au(III) hydroxide complexes and calcined in air at 400 °C. The parameters of local atomic surrounding for Au atoms in these catalysts were determined using XANES and EXAFS techniques at 12 and 296 K. In all samples, the only phase detected was metallic gold. A contraction of interatomic Au–Au distance (R1) and a gradual decrease in the coordination number for the first coordination shell of Au atoms (N1), as well as an increase in the Debye–Waller factor (σ) were observed with decreasing mean Au particle size.