Anomalous small-angle x-ray scattering from mesoporous noble metal catalysts

We present the analysis of a catalyst containingplatinum nanoparticles supported on mesoporous MCM-41silica by anomalous small-angle x-ray scattering (ASAXS).The analysis of this composite system by ASAXS is firststudied by use of model calculation. Here, it is shown thatthe full analysis must proceed by decomposing the scatteringdata measured at different energies of the incident beam intothree partial intensities. This evaluation is compared to asimplified method in which scattering curves measured attwo different energies are subtracted from each other. Thedifferent methods are applied to experimental data obtainedfrom platinum nanoparticles on anMCM-41 support material.The model calculations show that the simplified method leadsto large deviations especially at low q in ordered systems. Inthe semi-ordered material MCM-41, these deviations are lesspronounced, and the method of simple subtraction proves tobe a good approximation for q values higher than 0.1 nm−1