Revealing the Dynamic Behavior of Active Sites on Acid-Functionalized CeO 2 Catalysts for NO x Reduction

Unraveling the dynamics of the active sites upon CeO -based catalysts in selective catalytic reduction of nitrogen oxides by ammonia (NH -SCR) is challenging. In this work, we prepared tungsten-acidified and sulfated CeO catalysts and used operando spectroscopy to reveal the dynamics of acid sites and redox sites on catalysts during NH -SCR reaction. We found that both Lewis and Brønsted acid sites are needed to participate in the catalytic reaction. Notably, Brønsted acid sites are the main active sites after a tungsten-acidified or sulfated treatment, and the change of Brønsted acid sites significantly affects the NO removal. Moreover, acid functionalization promotes the cerium species cycle between Ce and Ce for the NO reduction. This work is critical to deeply understanding the natural properties of active sites, and it also provides new insights into the mechanism for NH -SCR over CeO -based catalysts.