Co-doping WO3-MoO3 enhances the low-temperature NH3-SCR activity of V2O5/TiO2 catalysts

To improve the low-temperature performance of V₂O₅/TiO₂ catalysts in the selective catalytic reduction of ammonia (NH₃-SCR), tungsten (W) and molybdenum (Mo) were incorporated into the V₂O₅/TiO₂ catalyst. A series of V-W-Mo/TiO₂ catalysts were synthesized using the incipient wetness impregnation method. Advanced characterization techniques, including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and NH₃ temperature-programmed desorption (NH₃-TPD), were utilized to examine the effects of WO₃ and MoO₃ co-doping on the performance of V/Ti catalysts. The findings reveal that the VW₁₀Mo_5.5/TiO₂ catalyst demonstrated exceptional performance, maintaining a NO conversion rate above 80 % across a broad temperature range of 190 °C to 400 °C. In comparison, the V₂O₅/TiO₂ catalyst required a temperature of 230 °C to achieve the same NO conversion rate, indicating that the co-doping of WO₃ and MoO₃ lowered the temperature for efficient NO conversion by 40 °C. Raman spectroscopy and XPS analyses revealed that the co-doping of WO₃ and MoO₃ increased the proportion of V⁴⁺ species and chemically adsorbed oxygen on the vanadium-titanium-based catalyst, which enhances low-temperature NH₃-SCR activity. Furthermore, the co-doping of WO₃ and MoO₃ significantly affected the migration and aggregation of vanadium species, converting surface monomeric vanadium oxide species into surface polymeric vanadium oxide species. Polymeric vanadium oxide species are crucial for enhancing the NH₃-SCR activity of the catalyst, with a high proportion of these species significantly boosting the NH₃-SCR activity under low-temperature conditions.