In-situ X-ray absorption spectroscopy investigations during the conditioning procedure of PtRu colloid catalysts

We present the first in situ characterization of the conditioning process of a Vulcan supported precatalyst based on PtRu nanoparticles with either aluminumorganic or tetraalcylammonimum protection shells, obtained by x-ray absorption spectroscopic measurements on the Pt LIII-edge. To perform these measurements, a suitable reaction cell was developed. In combination with results from transmission electron microscopy, these data provide the basis for a detailed understanding of the above-mentioned process. In detail, we find that whereas the increase in particle size during this process and thus agglomeration of particles is rather small, there is a reduction of disorder in both types of particles, especially in the ones with an aluminumorganic protection shell. Furthermore, we observe different behavior of the Pt component in the two different types of particles during the oxidative step of the conditioning process, as only in aluminumorganically stabilized particles Pt atoms are subject to oxidation, whereas in the other sample they remain strictly zerovalent. Tentatively, these findings can be related to the internal structure of the as synthesized particles as obtained from preliminary evaluation of Pt LIII EXAFS-spectra.