EXAFS analysis of an Ir/γ-Al2O3catalyst at elevated temperatures: evidence for a Gaussian pair distribution function

Abstract

The effect of temperature on the structure of an Ir/γ-Al₂O₃ catalyst has been investigated. It was found that the assumption of a Gaussian Debye–Waller factor was valid for a temperature up to at least 573 K, for both the Ir–Ir and the Ir–O contributions. Theoretical references were generated using FEFF7 for the Ir–Ir and the Ir–O contributions. From the results of the EXAFS analysis, we conclude that the inter-atomic potential of very small particles forces the metal atoms to move more harmonically. Consequently the Einstein temperature, which indicates the temperature at which anharmonicity becomes important, increases. The results show that at reaction temperatures it is possible to obtain information with XAFS spectroscopy about first the structure of supported small noble metal particles and second the structure of the metal–support interface.