In Situ and Simultaneous Observation of Palladium Redox and Oxygen Storage/Release in Pd/Sr-Fe-O Perovskite Catalysts Using Dispersive XAFS

We have succeeded in in situ and simultaneously observing the redox reaction of palladium and the oxygen storage/release process in a newly developed palladium-promoted Sr-Fe-O (Pd/Sr-Fe-O) catalyst during redox-gas cycles using dispersive X-ray absorption fine structure (XAFS) analysis at 673 K with a time resolution of less than 20 ms. The Pd/Sr-Fe-O catalyst, which exhibits high performance for automotive emission control, has a unique "multi-phase-domain" structure, where a single grain is composed of nano-sized domains of three phases: SrFeO3-delta, Sr4Fe6O13-delta and SrFe12O19-delta. In situ observation has shown a strong correlation between the redox of the palladium and the oxygen storage/release in the Pd/Sr-Fe-O catalyst, and the correlation factors differ between the reduction and oxidation reactions. The oxide phases exhibit a type of "oxygen buffer" effect in the oxidation cycle and delay the formation of Pd-O, resulting in the high performance of the catalyst.