Bimetallic AgFe systems on mordenite: Effect of cation deposition order in the NO reduction with C₃H₆/CO

Mono-and bimetallic systems of Ag, Fe, and Ag–Fe exchanged in sodium mordenite zeolite were studied in the reaction of NO reduction. The transition metal cations Ag and Fe were introduced by ion exchange method both at room temperature and 60 °C; modifying the order of component deposition in bimetallic systems. These materials were characterized by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), ultraviolet-visible spectroscopy (UV-Vis), X-Ray photoelectron Spectroscopy (XPS) and High-resolution transmission electron microscopy (HR-TEM). The XPS and UV–Vis spectra of bimetallic samples revealed that under certain preparation conditions Ag⁺ is reduced with the participation of the Fe²⁺/Fe³⁺ ions transition and is present in the form of a Ag reduced state in different proportions of Ag_m clusters and Ag⁰ NPs, influenced by the cation deposition order. The catalytic results in the NO reduction reaction using C₃H₆/CO under an oxidizing atmosphere show also that the order of exchange of Ag and Fe cations in mordenite has a strong effect on catalytic active sites for the reduction of NO.