Real-Time Insights into Sustainable Materials: Correlative Electron Microscopy and Synchrotron Techniques

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Catalytic materials are fundamental to a wide range of energy conversion technologies, (e.g. fuel cells), where their efficiency is governed by properties such as activity, stability, and selectivity. For sustainable catalysts, a long lifetime is important to ensure consistent performance over time, minimizing the need for replacement and reducing environmental impact. To optimize these materials for practical applications, a deep understanding of their structure and behaviour at the nanoscale is crucial. The complexity of catalytic reactions, often involving subtle atomic-scale changes during operation, necessitates the use of advanced characterization techniques. Transmission electron microscopy (TEM), along with complementary synchrotron-based methods, has proven indispensable for these investigations, enabling us to bridge the gap between structural features and catalytic performance.

Ex-situ TEM is a powerful tool for characterizing catalytic materials, providing high-resolution imaging and chemical analysis of catalysts in their static state. Techniques such as energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) allow precise determination of elemental composition and electronic structure. EDS can identify the spatial distribution of elements, while EELS provides insights into electronic states and bonding environments. In addition, TEM tomography offers three-dimensional reconstructions of catalyst particles, revealing their morphology and internal architecture at the nanoscale. However, ex-situ TEM is inherently limited to post-reaction analysis, which may not fully capture the dynamic changes occurring during catalysis, such as surface restructuring or particle sintering.

To overcome this limitation, in-situ TEM techniques are increasingly employed to observe catalytic processes in real-time under operating conditions. In-situ TEM allows for direct visualization of catalysts in gas or liquid environments, simulating actual reaction conditions, which is critical for understanding the behaviour of nanoparticles during catalysis. For example, in-situ TEM can reveal how nanoparticles evolve during reactions, including phase transformations, surface reconstruction, or dissolution processes.

The combination of in-situ TEM with synchrotron radiation techniques offers a more comprehensive understanding of catalytic materials. Synchrotron-based techniques such as X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) can provide complementary information at the atomic and electronic levels. XAS can reveal oxidation states, coordination environments, and electronic structure, while XRD provides information on crystalline phases and lattice parameters. Correlating TEM observations with synchrotron data enables to link atomic-scale structural changes directly to catalytic properties, offering a more complete picture of the mechanisms governing catalyst performance. In this presentation, several examples will be discussed to illustrate the power of TEM, in-situ TEM, and synchrotron techniques.