Multi-modal approach for active sites visualisation of noble-metal core-shell catalysts

Abstract

Heterogeneous catalysts are materials that do not have static structures and can change their morphology/surface composition depending on reaction conditions. These changes, especially at the atomic level, induce alterations in the chemical properties of the catalysts. Gradients are also expected at the catalytic reactor scale. Therefore, it is crucial to understand the relationships between catalyst structures and properties. Nowadays, with the development and improvement of synchrotron radiation facilities, the interest in applying complementary in situ/operando synchrotron techniques is growing. In situ approaches are presented as scale-dependent methods and have rarely been explored on a multiscale level although mechanisms of activation/deactivation need to be identified at different scales. The novelty of this project lies in the combination of in situ space and energy-resolved techniques, to obtain a comprehensive characterisation of catalysts under realistic working conditions. For this purpose, the catalytic reaction of carbon monoxide oxidation will be studied on a multiple scale using noble-metal core-shell nanoparticle catalysts with controlled shape and size. This research will employ synchrotron light techniques such as X-ray absorption spectroscopy and coherent X-ray diffraction imaging to understand the reaction mechanisms and monitor the structural evolution of catalysts with micrometric resolution through the catalytic bed and with nanometric resolution at the single-nanoparticle-level. Strains and defects changes on the catalysts occurring through the reaction will be correlated with their catalytic performances under specific hysteresis conditions. This research project will directly generate a new methodology for the in situ monitoring of catalysts and open a new route for the research and development of materials with applications in various domains. (AU)