Optimizing Selective Catalytic Reduction of NO with NH3 on Fe2O3/WO3 via Redox-Acid Synergy

An iron-tungsten oxide catalyst was developed for selective catalytic reduction of NO with NH3 (NH3-SCR) by supporting Fe2O3 nanoparticles onto hexagonal WO3 nanorods. The Fe2O3/WO3 catalyst showed much higher catalytic activity than Fe2O3 and WO3, as explained by the synergistic effects caused by acid sites (provided by WO3) and redox sites (provided by Fe2O3). X-ray diffraction and transmission electron microscopy techniques revealed that the crystal structures and morphologies of Fe2O3 and WO3 kept unchanged during the preparation of Fe2O3/WO3. NH3 adsorption curves, NH3 temperature programmed desorption, and temperature programmed surface reaction of NO demonstrated that WO3 possessed strong acidity but poor redox ability, whereas Fe2O3 had high redox ability but inadequate acidic property. Therefore, the enhancement in catalytic activity (when using Fe2O3/WO3 as a catalyst) should originate from the redox-acid synergy, as further evidenced by the low SCR activity of pure Fe2O3 and Fe2O3/TiO2 with low capacity for adsorbing NH3. In addition, Fe2O3/WO3 showed high activity and stability in the presence of K+, SO2, and H2O, demonstrating its potential in practical applications.