Sylwia Owczarek

Field Emission Microscopy to Study the Catalytic Reactivity of Binary Alloys at the Nanoscale

Catalysis plays a crucial role in modern industrial applications. The aim in every process involving catalysis is to obtain a high and sustainable conversion along with a high selectivity towards the desired product(s). In the case of heterogeneous catalysis, one of the ways to reach this goal is to design tailored nanoparticles that present a specific composition, shape and morphology. Such engineering of catalysts only works if one understands how the reaction proceeds on different morphologies and how the reaction may induce structural changes. Another way to improve the efficiency relies in the control of the catalytic reaction. For this, the study of the dynamics occurring at the surface of the catalyst is used to determine the reaction mechanism with better accuracy, which in turn opens the way to a rationale for assessing the reproducibility, the predictability and the controllability of the reaction. To improve a catalytic process, a fundamental understanding of the catalytic behavior of the active materials is thus required. Surface science studies had, and still have, a great impact on the understanding of catalytic systems. These studies are mainly performed on catalytic reactions occurring at the surface of pure metals. There is, however, an increasing interest in using alloy catalysts in industrial applications, which calls for in situ studies providing a fundamental understanding of the properties of alloy catalysts.

Nanoscale Imaging of Subsurface Oxygen Formation on Rhodium Catalysts

During a catalytic process, a catalyst may undergo changes of its structure or morphology, as well as modifications of its local composition, which is due to oxidation/reduction processes, surface segregation, or even the presence of subsurface species [1]. All these modifications may affect the activity and the selectivity of the catalyst and contribute to the ageing of the catalyst. To develop catalysts with improved efficiency, a fundamental understanding of the catalytic process is needed. The shape of the nanoparticle, its size, its local chemical composition and the synergistic influences of these features on the catalytic activity must be determined, down to the molecular level, to unravel the details of this reaction. Such studies gain significance if they are performed during the ongoing process so as to highlight transient behaviors that cannot be observed before and after reactions.