Catalytic removal of nitrogen monoxide, carbon monoxide and hydrocarbons
For the time being exhaust gas after-treatment represents a major challenge for internal combustion engines. Stricter future regulations will further enhance the demand for more efficient exhaust gas catalysts since increasing the noble metal loading or the overall catalyst amount is counterproductive. This is particularly important considering that more than 50% of Pt, 80% of Rh and 70% Pd of world production are going into the automotive industry.
Among different catalytic systems, the three way catalyst (TWC) for simultaneously removing CO, HCs and NOx emissions of gasoline engines is the most known. However, the number of fundamental studies to establish catalyst structure-activity relationships is very low. Moreover, in situ/operando investigations are hardly available. Hence, we aim at unravelling functionality details (local structure, interaction with reactant molecules) for all main components of the TWC: Pd and Rh, as active sites, and CeO2 as oxygen buffer component for balancing the fluctuations in the exhaust gas stoichiometry.
For this purpose, we investigate the L1 and the L2,3 edges of these elements by using the recently commissioned tender X-ray (1.5 – 5 keV) emission spectrometer at the ID26 beamline. The L-edges have the important advantage over the K-edge that the spectral resolution is considerably better, revealing details that allow for precise characterization of the electronic structure and local coordination. The project includes the development of an in situ /operando cell for the tender X-ray chamber, which allows us to uncover the behaviour of the active sites during TWC operation.
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