The design of photocatalysts for the removal of NOx at normal temperatures—Copper (I) and silver (I) ion catalysts anchored within zeolite cavities

Abstract

The Cu+/ZSM-5 and Ag+/ZSM-5 catalysts were prepared by a combination of ion-exchange and thermovacuum treatments. In situ photoluminescence, ESR, XAFS, UV-VIS and FT-IR measurements of the catalysts revealed that within the cavity of the ZSM-5 zeolite, the Cu+ ion or Ag+ ion exists in an isolated state. UV irradiation of the catalysts in the presence of NO at normal temperature led to the formation of N2 and O2 for Cu+/ZSM-5 and N2, N2O and NO2 for Ag+/ZSM-5, indicating that the isolated Cu+ ion or Ag+ ion acts as a photocatalyst for the direct decomposition of NO. However, the Cu+/ZSM-5 catalyst loses its photocatalytic reactivity under the coexistence of O2, while the Ag+/ZSM-5 catalyst maintains its reactivity under the coexistence of O2 and H2O.