Materials Chemistry, Short talk
Mat-027

Surface Organometallic Chemistry on a MEMS Chip: Operando TEM Study of Dynamics of Alloyed PtGa Nanoparticles during Propane Dehydrogenation 

M. Ciuoli1, E. Brack1, J. Landis1, M. Plodinec1,2, C. Copéret1*
1ETH Zürich, Department of Chemistry and Applied Biosciences, 2Scientific Center for Optical and Electron Microscopy, ETH Zürich

Establishing structure-activity relationships in heterogeneous catalysis remains challenging due to multi-component complexity.[1] Surface Organometallic Chemistry (SOMC) minimizes this complexity, enabling the formation of well-defined (bi)metallic nanoparticles with tailored interfaces.[2] However, operando (Scanning) Transmission Electron Microscopy ((S)TEM) imaging of heterogeneous catalysts is often hindered by standard sample preparation (sonication/drop-casting). These conventional methods cause inhomogeneous catalyst distribution and charging effects from poor physical contact between the catalyst and the chip, compromising spatial resolution.[3]To overcome these limitations, the SOMC approach is used to synthesize tailored (bi)metallic catalysts directly onto an Al2O3-coated MEMS chip,[4] facilitating a uniform dispersion of nanoparticles, and therefore a more reproducible correlation of structure-activity relationships.

We applied this novel methodology to study alloyed PtGa NPs supported on a Al2O3-coated MEMS chip for propane dehydrogenation.[5] Using a double aberration Cs-corrected (S)TEM operated at 300 kV and equipped with a dual SDD-EDX detector system, we monitored the structural dynamics of alloyed PtGa nanoparticles in different gas atmospheres. under He, High-angle annular dark-field STEM imaging revealed that air-exposed particles exhibit a core-shell like structure with an amorphous GaOx shell, which is then reduced when exposed to H2 at 600°C. The successful formation of a homogenoeus alloy is confirmed by STEM EDX elemental mapping (Figure 1). When exposed to the diluted propane mixture, a dynamic behaviour assigned to the presence of Ga alloyed species (from DFT-based metadynamics calculation) and the concomitant formation of a metastable Pt2C-phase are observed. Additionally, the presence of “holes” or missing atoms is observed, likely due to the formation of stiff carbon-chains limiting the movement of the Ga atoms.

[1]   Schlögl R., et al.; Angewandte Chemie International Edition, 2015, 54, 3465-3520.
[2]  Copéret C., et al.; Accounts of Chemical Research, 2019, 52, 1697-1708.
[3]  Yue S., et al.; Nature Communications, 2024, 15, 4678.
[4] Brack E., et al.; Journal of the American Chemical Society, 2026, 148, 19, 19722-19729.
[5]  Sakamoto K., et al.; Journal of the American Chemical Society, 2025, 147, 25, 22041-22052.