Advanced Elemental Characterization during Pt-In Catalyst Formation by Wavelet Transformed X-ray Absorption Spectroscopy

Complementary to conventional X-ray,absorption near edge structure ()CANES) and Fourier transformed (FT) extended X-ray absorption,fine structure (EXAFS) analysis, the systematic application of wavelet transformed (WT), XAS is shown to disclose the physicochemical mechanisms governing Pt In catalyst formation. The simultaneous k- and R-space resolution of the WT XAS signal allows for the efficient allocation of the elemental nature, to each R-space peak. Because of its elemental discrimination capacity, the technique delivers structural models-which can subsequently serve as an input for quantitative FT EXAFS modeling. The advantages and limitations of applying WT XAS are demonstrated (1) before and (2), after calcination to 650 degrees C of a Pt(acac)(2) impregnated Mg(In)(Al)O-x support and (3) after subsequent H-2 reduction to 650 degrees C. Combined XANES, FT, and WT XAS analysis shows that the acac ligands of the Pt:precursor decompose during calcination, leading to atomically dispersed Pt4+ cations on the Mg(In)(Al)O-x support. H-2 reduction treatment eventually results in the formation of 1.5 nm Pt-In alloyed nanoparticles. Widespread use and systematic application of wavelet,based XAS can potentially reveal in greater detail the intricate mechanisms involved in catalysis, chemistry, and related fields