In Situ and Simultaneous Observation of Palladium Redox and Oxygen Storage/Release in Pd/Sr­Fe­O 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 Sr­Fe­O (Pd/Sr­Fe­O) catalyst during redox-gas cycles using dispersive X-ray absorption fine structure (XAFS) analysis at 673K with a time resolution of less than 20ms. The Pd/Sr­Fe­O 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: SrFeO3¹¤ ,S r4Fe6O13¹¤ and SrFe12O19¹¤. In situ observation has shown a strong correlation between the redox of the palladium and the oxygen storage/release in the Pd/Sr­Fe­O 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 Pd­O, resulting in the high performance of the catalyst.