Au-Rh nanoalloys were prepared from colloidal solution . The growth mechanism was studied in situ by TEM in a graphene liquid cell [2-3]. Then, in an environmental sample holder ,the influence of oxygen or hydrogen adsorption on the structure of AuRh/TiO2 catalysts was observed at a pressure of a few mbar and at room temperature.
2. Growth mechanism
The colloidal solution was encapsulated in a graphene oxide liquid cell and directly observed in a standard electron microscope. The particle growth was initiated under the electron beam.
The same area was observed during about 80 s and images were recorded every 5 s. The average particle size increases until 4 nm. The density number plotted in fig. 1, indicates a maximal density after 25 s, then a drop after 50 s, corresponding to a growth mechanism by direct adsorption of the monomers. This process is followed by coalescence of the particles, as directly seen in fig. 2.
3. Segregation in hydrogen
Au-Rh nanoparticles with an homogeneous structure, and supported on rutile TiO2 nanorods powders, were observed during oxidation- reduction cycles in an environmental sample holder. In the largest NPs, core- shell formation was clearly observed during hydrogen adsorption, as seen in figure 3. On the other hand, the observation of Au-Rh NPs annealed ex situ in H2 at 400 °C, also shows the core- shell contrast which was not visible before H2 treatment.
The strong interaction between hydrogen and Rh is certainly responsible for the surface segregation of Rh.
We thank the ANR DINAMIC -11-BS10-009 for financial support and Région PACA for a grant given for the PhD thesis of A. De Clercq.
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To cite this abstract:Astrid De Clercq, Laurent Piccolo, Suzanne Giorgio; In situ study of Au-Rh nanoalloys. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/in-situ-study-of-au-rh-nanoalloys/. Accessed: December 4, 2023
EMC Abstracts - https://emc-proceedings.com/abstract/in-situ-study-of-au-rh-nanoalloys/