Structure and Chemistry of Cu–Fe–Al Nanocomposite Catalysts for CO Oxidation

High-active Fe–Al and Cu–Fe–Al nanocomposite catalysts were synthesized by fusion of aluminium, iron, and copper salts and then tested in the oxidation of CO. It was found that the activity of Fe–Al catalysts depends on the Fe concentration and the maximum is achieved when the Fe₂O₃ content is approximately 82 wt%. The addition of Cu leads to a significant increase in activity. Using adsorption techniques, X-ray diffraction, X-ray absorption spectroscopy, and Fourier-transform infrared spectroscopy, morphology, structure, and chemistry of the catalysts were studied. It was shown that the Fe–Al catalysts consist of Fe₂O₃ and Al₂O₃ phases mainly. Alumina is in an amorphous state whereas iron oxide forms nanoparticles with the protohematite structure. The Al³⁺ cations partially dissolute in the Fe₂O₃ lattice. X-ray absorption spectroscopy indicated that the Cu–Fe–Al catalysts in addition contain CuO and CuFe₂O₄ oxides in an amorphous state.