Abstract
Hexagonal WO3 crystals with [1 1 0] and [0 0 1] orientations (denoted as H-110 & H-001) were synthesized and impregnated with 5 wt% V2O5 for NH3-SCR catalysis. H-110 with dominant (0 0 1) exposed facet possesses 72% NOx conversion at 400 °C while H-001 with dominant (1 0 0) exposed facet only achieves 17%. The maximal NOx conversion over V/H-110 and V/H-001 catalysts was enhanced to 96% and 47%, respectively. The catalysts were characterized by H2 temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) of NH3, X-ray photoelectron spectroscopy (XPS), Raman, ultraviolet-visible (UV-vis) and diffuse reflection infrared Fourier transform (DRIFT) spectroscopy. The more coordinative unsaturated W6+ atoms on (0 0 1) facet generated more acid sites and NH3 was more strongly adsorbed on H-110 surface. The better match relationship between vanadia and WO3 (0 0 1) exposed facets led to the formation of more polymeric vanadates on V/H-110 catalyst. The higher proportioned V4+ and chemisorbed oxygen on V/H-110 catalyst also facilitated NH3-SCR reaction.
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