Synergistic effects and individual roles of Ce–O–W sites in the NH3–SCR redox cycle-acid cycle

The selective catalytic reduction of NO with NH 3 (NH 3 −SCR) reaction is governed by the interplay of surface acidity and redox activity, yet the mechanism of their cooperation remains elusive. Herein, Ce–O–W linkages were constructed on Ce/ZrO 2 to couple Ce 4+ /Ce 3+ redox cycle with tungsten-derived acidity. Operando DRIFTS and transient experiments revealed that gaseous NO reacts directly with NH 3 adsorbed on Lewis Ce 4+ sites, following an Eley–Rideal pathway. Brønsted acid sites from Ce–O–W acted as NH 4 + reservoirs, dynamically replenishing Lewis-bound NH 3 and sustaining continuous reactivity. Operando UV–vis spectroscopy confirmed that NO + NH 3 exposure reduced Ce 4+ to Ce 3+ , while O 2 re-oxidized Ce 3+ to Ce 4+ , establishing the redox cycle. Density functional theory calculations supported that NH 3 dehydrogenation on Ce sites and subsequent coupling with gaseous NO were energetically favorable, while O 2 -assisted Ce 3+ re-oxidation required the highest energy barrier. These results highlight the cooperative function of Ce–O–W acid–redox site in promoting SCR activity through dynamic L–NH 3 /B–NH 4 + interplay and sustained Ce redox cycling.