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Promotion of 2.73% Fe 2 O 3 in an in-house-made V 2 O 5 -WO 3 /TiO 2 (VWT) and a commercial V 2 O 5 -WO 3 /TiO 2 (c-VWT) has been investigated as a cost effective approach to the suppression of N 2 O formation in the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The promoted VWT and c-VWT catalysts all gave a significantly decreased N 2 O production at temperatures >400 • C compared to the unpromoted samples. However, such a promotion led to the loss in high temperature NO conversion, mainly due to the oxidation of NH 3 to N-containing gases, particularly NO. Characterization of the unpromoted and promoted catalysts using X-ray diffraction (XRD), NH 3 adsorption-desorption, and Raman spectroscopy techniques could explain the reason why the promotion showed much lower N 2 O formation levels at high temperatures. The addition of Fe 2 O 3 to c-VWT resulted in redispersion of the V 2 O 5 species, although this was not visible for 2.73% Fe 2 O 3 /VWT. The iron oxides exist as a highly-dispersed noncrystalline α-Fe 2 O 3 in the promoted catalysts. These Raman spectra had a new Raman signal that could be tentatively assigned to Fe 2 O 3 -induced tetrahedrally coordinated polymeric vanadates and/or surface V-O-Fe species with significant electronic interactions between the both metal oxides. Calculations of the monolayer coverage of each metal oxide and the surface total coverage are reasonably consistent with Raman measurements. The proposed vanadia-based surface polymeric entities may play a key role for the substantial reduction of N 2 O formed at high temperatures by NH 3 species adsorbed strongly on the promoted catalysts. This reaction is a main pathway to greatly suppress the extent of N 2 O formation in NH 3 -SCR reaction over the promoted catalysts.