Mechanistic insight into the dynamic transformation of acid sites on ceria supported molybdenum oxide catalyst for NOx reduction

Abstract

Acidity is a crucial factor limiting the application of ceria-based catalyst for selective catalytic reduction (SCR) of NOx with NH3. Unravelling the participation mechanism of acid sites on ceria-based catalyst is imperative but still lacking. Herein, by tuning the electronic interaction between MoOx and CeO2 nanosheet with numerous pits (P-CeO2) via controlling the number of surface pits of P-CeO2, we demonstrate that electronic interaction strongly determines the acidity properties of catalyst to modulate the catalytic performance. The MoOx/P-CeO2 exhibits much better catalytic activity, N2 selectivity and tolerance to SO2 and H2O than MoOx/CeO2 with few pits in a temperature range of 250–400 °C with a gas hourly space velocity (GHSV) of 60,000 h−1, which is due to the highly dispersion of Mo-O-Mo structure over P-CeO2 as determined by Raman. Furthermore, XPS and DFT calculations demonstrate that electrons transfer from P-CeO2 to MoOx result in a unique dynamic transformation from Brønsted acid site to Lewis acid site, enhancing the catalytic activity. This work increases the acidity sites on the catalyst by regulating the electron oxide-support interaction, which provides a new strategy for designing highly efficient ceria-based SCR catalysts.