Enhanced Catalytic NO Reduction in NO-CO-C3H6-O2 Reaction Using Pseudo-Spinel (NiCu)Al2O4 Supported on γ-Al2O3

This study aims to clarify the effect of Ni addition on the enhancement of the NO reduction activity of Cu/Al2O3, which possesses high thermal durability, and to elucidate the associated structure-catalysis relationship. Thermal aging of Ni and Cu supported on gamma-Al2O3 at a high temperature (900 degrees C) induced the formation of a pseudo-spinel (NiCu)Al2O4 solid solution on the gamma-Al2O3 surface, which was observed using X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy techniques. Owing to the co-presence of Ni, the preferential occupation of octahedral sites by Ni increased the number of tetrahedrally coordinated Cu2+ ions, which played a key role in the reduction of NO in a stoichiometric NO-CO-C3H6-O-2 reaction. XPS analysis revealed that Cu active sites with electron-rich states were formed in pseudo-spinel (NiCu)Al2O4 owing to electron donation from Ni to Cu, which promoted NO adsorption on Cu+ and accelerated NO reduction. The tetrahedrally coordinated Cu formed on the pseudo-spinel oxide was structurally robust, and its local structure remained unchanged even after the redox cycle occurred at a high temperature; this indicated that the formation of pseudo-spinel (NiCu)Al2O4 was effective for the enhancement of NO reduction activity and thermal durability.

Automated summary

The addition of nickel increased the NO reduction activity of Cu/Al2O3 by forming a NiCuAl2O4 solid solution, promoting NO adsorption on Cu+ and accelerating the NO reduction reaction.