Rational design of 3D hierarchical foam-like Fe2O3@CuOx monolith catalysts for selective catalytic reduction of NO with NH3

Herein, we have rationally designed and originally fabricated a high-performance monolith catalyst based on 3D hierarchical foam-like Fe2O3@CuOx for selective catalytic reduction (SCR) of NO with NH3. The Fe2O3@CuOx foam catalyst was synthesized by calcining the Cu foam in air first to form CuOx foam with CuOx nanowire arrays on the surface and then the Fe2O3 could be in situ formed on the surface of CuOx through the reaction in the interfacial region between the aqueous solution of Fe2+ and CuO via a hydrothermal method. This catalyst was mainly characterized by the techniques of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, H-2 temperature-programmed reduction, NH3/NO + O-2 temperature-programmed desorption and in situ diffuse reflectance infrared Fourier transform spectroscopy. Both the atomic concentration of Cu+ and chemisorbed oxygen species are enhanced by the coating of Fe2O3, which facilitates NO attack on active sites, resulting in the in situ formation of NO2 and promoting the fast SCR reaction. Moreover, there is a strong interaction between CuOx and Fe2O3, which could not only lead to better reduction ability but also raise the acid amount and enhance the acid strength as well as NOx adsorption ability. Based on these favourable properties, the Fe2O3@CuOx catalyst exhibits a higher activity and more extensive operating temperature window than the catalyst without Fe2O3. More importantly, the Fe2O3 not only prevents the generation of ammonium sulfates from blocking the active sites but also inhibits the formation of copper sulfates, resulting in a high SO2-tolerance. In addition, the catalyst also displays favourable stability and H2O resistance. The rational design of 3D hierarchical foam-like Fe2O3@CuOx paves a new way for the development of environmentally-friendly and high-performance monolith deNO(x) catalysts.