Synthesis and characterisation of Au/Fe2O3 catalysts

Abstract

Iron oxide supported gold catalysts, and control samples containing no gold, were prepared by the “as-precipitated” method and by the “solution combustion” method. These were studied using BET isotherm, powder and single crystal XRD, TEM, SEM, EDS, XPS and in situ DRIFTS.

Measurements of activity for the oxidation of CO were carried out using a tube reactor attached to a residual gas analyser.

BET surface areas varied from 37 to 134 m2/g, with XRD patterns showing the production of haematite, and γ-Fe2O3 or magnetite. Scherrer analysis of the gold peaks gave gold crystallite sizes between 42 and 139nm. Assessing the size of gold particles by TEM gave values between 14.0 and 29.7nm. SEM of the samples indicated some very large gold particles on some catalysts and that all samples had a similar physical support structure.

The catalysts produced were of variable activity for CO oxidation, although none were as active as certain nominally similar materials previously reported in the literature.

The more reactive samples had the higher surface areas and XPS showed that the more active catalysts contained gold in the cationic state, with DRIFTS showing the presence of a broad band at 2005cm-1 due to adsorbed CO on the more active catalysts.