Revealing the Dynamic Behavior of Active Sites on Acid-Functionalized CeO2 Catalysts for NO x Reduction

Unraveling the dynamics of the active sites upon CeO2-based catalysts in selective catalytic reduction of nitrogenoxidesby ammonia (NH3-SCR) is challenging. In this work, we preparedtungsten-acidified and sulfated CeO2 catalysts and usedoperando spectroscopy to reveal the dynamics of acid sites and redoxsites on catalysts during NH3-SCR reaction. We found thatboth Lewis and Bronsted acid sites are needed to participatein the catalytic reaction. Notably, Bronsted acid sites are themain active sites after a tungsten-acidified or sulfated treatment,and the change of Bronsted acid sites significantly affects theNO( x ) removal. Moreover, acid functionalizationpromotes the cerium species cycle between Ce4+ and Ce3+ for the NO x reduction. Thiswork is critical to deeply understanding the natural properties ofactive sites, and it also provides new insights into the mechanismfor NH3-SCR over CeO2-based catalysts.