Continuous De-NO_<i>x</i> underRich/Lean Cycles by Multifunctional Catalysis of Platinum-Loaded Mordenites

Limited catalytic methods have been reported for urea-free lean NO_<i>x</i> emission control. This study reports a continuous and cyclic de-NO_<i>x</i> system utilizing mordenite-supported low-loading (0.3 wt %) platinum, Pt(0.3)/MOR, as a multifunctional catalytic and NH₃ storage material. Under alternating feeds of rich (0.1% NO + 0.5% CO + 1% H₂O) and lean (0.1% NO + 2% O₂ + 1% H₂O) gas mixtures, Pt(0.3)/MOR demonstrated higher de-NO_<i>x</i> efficiency under relatively lean conditions compared to the steady-state reaction in a temperature range of 300–500 °C. The de-NO_<i>x</i> mechanism under periodic rich/lean conditions on Pt(0.3)/MOR was investigated using operando infrared experiments. During the rich period, the Pt-catalyzed water–gas shift reaction gives H₂ which reduces NO into in situ formed NH₃. The generated NH₃ is subsequently captured by the Brønsted acid sites of the zeolite support. In the subsequent lean period, NO is reduced by adsorbed NH₃ on Pt sites. This study presents a new multifunctional material for a urea-free de-NO_<i>x</i> system, offering a potential alternative for automotive de-NO_<i>x</i> applications.