Cation distribution in Cu(Cr2–xAlx)O4 and Cu(Fe2–xAlx)O4 according to neutron-diffraction studies and their catalytic properties in the water-gas shift reaction

• Published in: Surface investigation, x-ray, synchrotron and neutron techniques x-ray, synchrotron and neutron techniques, 2016-11, Vol.10 (6), p.1161-1168
• Main Authors: Plyasova, L. M., Minyukova, T. P., Yurieva, T. M., Bobrikov, I. A., Balagurov, A. M.
• Format: Article
• Language: English
• Subjects: Aluminum; Chemistry and Materials Science; Copper; Materials Science; Shift reaction; Spinel; Structural analysis; Substitutes; Surfaces and Interfaces; Thermal decomposition; Thin Films
• ISSN: 1027-4510; 1819-7094
• DOI: 10.1134/S102745101605058X

The neutron structural analysis of Cu(Cr 2 − x Al x )O 4 and Cu(Fe 2 − x Al x )O 4 (0 ≤ x ≤ 2) nanopowders is performed. The samples are prepared by the thermal decomposition of mixed hydroxy compounds at 900°C. Different spinel phases are shown to form in Cu(Cr 2 − x Al x )O 4 : a tetragonally distorted phase when x ≤ 1.0, a cubic phase when x > 1.25, and a mixture of both phases when 1 < x < 1.25. As Al 3+ ions substitute Cr 3+ ions, a number of Cu 2+ ions move from tetrahedral spinel sites to octahedral ones: the degree of inversion δ changes from 0 for CuCr 2 O 4 to ≈0.4 for CuAl 2 O 4 . In the Cu(Fe 2 − x Al x )O 4 system, the cubic spinel forms at all x , except x = 0. The degree of inversion δ varies from 1 for CuFe 2 O 4 to ≈0.4 for CuAl 2 O 4 as Al 3+ ions substitute Fe 3+ ions. The change in the activation energy of the water-gas shift reaction correlates with the inversion of Cu-containing spinels.