The spatial distribution of Ce(3+) and Ce(4+) in each particle of Ce2 Zr2 Ox in a three-way conversion catalyst system was successfully imaged during an oxygen storage/release cycle by scanning X-ray absorption fine structure (XAFS) using hard X-ray nanobeams. For the first time, nano-XAFS imaging visualized and identified the modes of non-uniform oxygen diffusion from the interface of Pt catalyst and Ce2 Zr2 Ox support and the active parts in individual catalyst particles.

The spatial distribution of Ce 3+ and Ce 4+ in each particle of Ce 2 Zr 2 O x in athree-wayconversion catalyst system was successfully imaged during an oxygen storage/release cycle by scanning X-ray absorption fine structure (XAFS) using hardX-raynanobeams.For the first time,nano-XAFS imaging visualizeda nd identified the modes of non-uniform oxygen diffusion from the interface of Pt catalyst and Ce 2 Zr 2 O x support and the active parts in individual catalyst particles.Heterogeneous solid catalysts are utilized for various chemical processes and are intrinsically non-uniform with respect to structure.S olid catalysts are typically in powder form, which is an assembly of non-uniform particles with different structural components (morphology,s urface structure,d omain boundary,o xygen content, and so forth). [1] In practice,the reactivity of asolid catalyst is evaluated based on the average of these structural components,and as aresult it remains difficult to understand the real variation of the active parts in ah eterogeneous catalyst. To solve this problem, spatially resolved imaging of chemical states in an individual catalyst particle is highly sought to reveal the active parts and non-uniform reaction modes at the nanoscale.Ce is ak ey element for the oxygen storage/release function in at hree-way catalyst system for clean-up of gaseous automobile exhaust;aredox process between Ce 3+ and Ce 4+ controls oxygen content in these catalyst systems. [2] However,itiswell-known that only Ce species with extensive surface defects can contribute to the redox process in pure ceria, which offers insufficient oxygen storage/release capacity.C e 2 Zr 2 O x (CZ; x = 7-8) solid-solution crystal contains an ordered arrangement of Ce and Zr atoms and exhibits excellent oxygen storage/release properties. [3] Almost 90 %ofthe Ce atoms in CZ bulk can participate in the redox