Insights into the Synergistic Promotion Effect of Cu and W Modification on the Catalytic Performance of α-Fe₂O₃ for NH₃-SCR of NO<i>_<i>x</i></i>

A dual-element modification strategy was proposed to promote the catalytic performance of the α-Fe₂O₃ catalyst for the selective catalytic reduction of NO<i>_<i>x</i></i> by NH₃ (NH₃-SCR of NO<i>_<i>x</i></i>) at both low and high temperatures. By optimizing the loading amount of CuO (4 wt %) and WO₃ (5 wt %), a wide operating temperature window (150-350 °C) was achieved on the modified α-Fe₂O₃ catalyst (W₅/Cu₄/Fe). Further characterizations revealed that the enhanced low-temperature activity could be attributed to the improved redox performance of α-Fe₂O₃ through CuO modification, while the superior high-temperature activity was primarily ascribed to the enhanced surface acidity induced by WO₃ modification. The synergistic effect of CuO and WO₃ modifications facilitated the NH₃-SCR reaction on the modified α-Fe₂O₃ catalysts to efficiently proceed through the Eley-Rideal (E-R) mechanism pathway. This provided compelling evidence that the catalytic performance of NH₃-SCR catalysts at different temperatures was dominantly governed by distinct factors (e.g., redox property and surface acidity), offering valuable insights for the rational design of robust catalysts for NO<i>_<i>x</i></i> abatement.