Oxidation and phase transfer of individual Cr-doped dendritic FeOx particles visualized by full-field nano-XAFS spectroimaging

Iron oxides with various compositions and polymorphs have been widely used as compounds that require reversible redox properties, such as catalysts. However, partial decomposition during phase transitions often causes irreversible degradation of the redox properties of iron oxides. Cr doping into the crystalline framework of iron oxide dendrites improves the stability of the structural transformation of iron oxides. We spatially visualized the FeOx-dendrite phase distribution during oxidation in crystalline dendritic FeOx and Cr-FeOx particles by full-field nano-X-ray absorption fine structure spectroimaging. The spectroimaging visualized propagation in the phase transitions in the individual FeOx particles and changes in the phase transition behaviors of the Cr-FeOx particles. The statistical analysis of the spectroimaging data revealed the phase transition trends in parts of the FeOx and Cr-FeOx particles in three Fe density zones (particle thicknesses) and the probability densities of the phase proportions in the dendrites.

Automated summary

Iron oxides are widely used as catalysts due to their reversible redox properties, but phase transitions can cause irreversible degradation. By doping Cr into the crystalline framework of iron oxide dendrites, the stability of the structural transformation of iron oxides is improved. Nano-X-ray absorption fine structure spectroimaging was used to visually observe the phase distribution of FeOx-dendrites and Cr-FeOx particles during oxidation, revealing the phase transition trends and probability densities in different Fe density zones.