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

Acidity is a crucial factor limiting the application of ceria-based catalyst for selective catalytic reduction (SCR) of NO x with NH 3 . Unravelling the participation mechanism of acid sites on ceria-based catalyst is imperative but still lacking. Herein, by tuning the electronic interaction between MoO x and CeO 2 nanosheet with numerous pits (P-CeO 2 ) via controlling the number of surface pits of P-CeO 2 , we demonstrate that electronic interaction strongly determines the acidity properties of catalyst to modulate the catalytic performance. The MoO x /P-CeO 2 exhibits much better catalytic activity , N 2 selectivity and tolerance to SO 2 and H 2 O than MoO x /CeO 2 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-CeO 2 as determined by Raman. Furthermore, XPS and DFT calculations demonstrate that electrons transfer from P-CeO 2 to MoO x 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.