Oxygen-diffusion-driven oxidation behavior and tracking areas visualized by X-ray spectro-ptychography with unsupervised learning

Abstract

Oxygen storage and release with oxygen diffusion in the bulk of the cerium-zirconium solid solution oxide Ce 2 Zr 2 O x (x = 7-8), which possesses an atomically ordered arrangement of cerium and zirconium atoms, is the key to three-way exhaust catalysis. Oxygen storage proceeds via heterogeneous oxygen diffusion into the vacant sites of Ce 2 Zr 2 O 7 particles, but the heterogeneous oxygen diffusion track is erased after oxygen storage in the Ce 2 Zr 2 O x bulk. Here we show three-dimensional hard X-ray spectro-ptychography to clearly visualize the three-dimensional cerium valence map in Ce 2 Zr 2 O x particles, and unsupervised learning reveals the concealed oxygen-diffusion-driven three-dimensional nanoscale cerium oxidation behavior and tracking areas inside individual mixed-oxide particles during the oxygen storage process. The described approach may permit the nanoscale chemical imaging of reaction tracking areas in solid materials.

X-ray Spectroptychography

“…Hirose et al examined cerium oxidation states and oxygen diffusion in bulk Ce 2 Zr 2 O x ( x = 7–8) with the aid of unsupervised learning and examined the relationship between morphology and reactivity, suggesting oxidation pathways in the solid catalyst. 31 Yuan et al 32 examined ZnO-coated alumina aerogels prepared by atomic layer deposition to derive high-spatial resolution ZnO chemical maps. Figure 7 presents an example of the 3D chemical mapping of Al 2 O 3 and ZnO phases from a study by Yuan et al, where the locations of ZnO and Al 2 O 3 were determined by ptychographic imaging at and below the Zn L 3 and Al K edges, respectively.…”

Principles of Different X-ray Phase-Contrast Imaging: A Review

“…In 2019, Hirose used X-ray spectroptychography to visualize the three-dimensional cerium valence map in Ce 2 Zr 2 O x (x = 7-8) particles. This achievement may permit the chemical imaging of reaction tracking areas at the nanoscale in solid materials [73]. In 2020, the fragmentation behavior of polyolefin catalysts was visualized in 3-D for the first time with this method by Bossers et al [74].…”

Decisive Structural and Functional Characterization of Halide Perovskites with Synchrotron

“…X-ray ptychography can also be combined with XAS to map the chemical composition of perovskite materials with high spatiospectral resolution by conducting an X-ray ptychography series across the absorption edges of target elements. 47,48 In addition, if one collects the coherent XRD patterns near a certain Bragg condition (e.g., vicinity of a particular hkl Bragg peak) exiting from an isolated crystalline object, the lattice displacement distribution within the individual crystal can be further extracted in addition to 3D morphology of the sample by retrieving the phase of the diffracted waves. Recently, this unique capability of BCDI has enabled imaging of individual grains in polycrystalline thin films and reveals strain distribution as well as dynamics of dislocations.…”