Steering the structure and reactivity of Ag/Al₂O₃ by the addition of multi-functional WO_x for NO_x reduction by ethanol

Ag/Al₂O₃ has shown promising deNO_x activity for (O)HC-SCR but has not yet been commercialized due to its narrow operating temperature range. Here, we developed AgW/Al₂O₃ exhibiting superior reactivity for ethanol-SCR compared to Ag/Al₂O₃ in the entire reaction temperature range. STEM-EDS visibly confirmed the hierarchical structure of AgW/Al₂O₃ where W was highly dispersed over Al₂O₃, and Ag species in contact with W had a narrow size distribution. UV–vis, H₂-TPR, and DRIFT results demonstrated that the abundant metallic Ag in AgW/Al₂O₃ accelerated the activation of ethanol into acetaldehyde, leading to improved NO_x conversion at low to medium temperatures, while ethylene formed over W-induced Brønsted acid sites appeared to contribute to maintaining the high-temperature deNO_x capacity. DFT calculations further supported that AgW/Al₂O₃ is more reactive toward acetaldehyde formation than Ag/Al₂O₃, and the corresponding active phases of AgW/Al₂O₃ were predicted to be predominantly metallic Ag along with Ag ionically bonded with WO₃.