Using SAXS for Determining the Sizes of Gold Nanoparticles in Au/C Catalysts: Advantages over Other Methods

The advantages of using SAXS along with the masking liquid technique for determining the sizes of supported metal particles over the standard TEM and XRD methods, usually used for these purposes, were shown in the case of Au/C catalysts. Particle size distributions of gold in a wide range (1–50 nm) were obtained from the SAXS data, including for all size fractions present in the samples. The mass fractions of X-ray amorphous gold particles smaller than 4 nm (W_SAXS) were determined. The oxidative treatment of the carbon support before the deposition of the metallic gold precursor complexes has a significant effect on the size distribution of gold particles in the final catalyst. A comparison of the experimental rates of CO oxidation with an excess of moist air at 40°C on Au/C catalysts with the W_SAXS values found for these catalysts showed that the catalytic activity increased exponentially as W_SAXS increased. The Au/C catalysts with W_SAXS ≥ 80% showed high activity in the oxidation of CO.