The Relationship between the Structural Characteristics of α-Fe2O3 Catalysts and Their Lattice Oxygen Reactivity Regarding Hydrogen

In this paper, the relationship between the structural features of hematite samples calcined in the interval of 800-1100 & DEG;C and their reactivity regarding hydrogen studied in the temperature-programmed reaction (TPR-H-2) was studied. The oxygen reactivity of the samples decreases with the increasing calcination temperature. The study of calcined hematite samples used X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Raman spectroscopy, and their textural characteristics were studied also. According to XRD results, hematite samples calcined in the temperature range under study are monophase, represented by the a-Fe2O3 phase, in which crystal density increases with increasing calcination temperature. The Raman spectroscopy results also register only the a-Fe2O3 phase; the samples consist of large, well-crystallized particles with smaller particles on their surface, having a significantly lower degree of crystallinity, and their proportion decreases with increasing calcination temperature. XPS results show the a-Fe2O3 surface enriched with Fe2+ ions, whose proportion increases with increasing calcination temperature, which leads to an increase in the lattice oxygen binding energy and a decrease in the a-Fe2O3 reactivity regarding hydrogen.

Automated summary

This paper investigates the relationship between the structural features of hematite samples and their reactivity towards hydrogen in the temperature-programmed reaction (TPR-H-2) after calcination at temperatures ranging from 800 to 1100 °C. The reactivity of the samples decreases as the calcination temperature increases. Various techniques, including X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and Raman Spectroscopy, were used to analyze the textural characteristics of the calcined samples. The results indicate that the calcined hematite samples mainly consist of the α-Fe2O3 phase, with an increase in crystal density and a decrease in the proportion of smaller particles on the surface as the calcination temperature rises.