Fe-induced transformation of OMS-2 to MnO with tailored oxygen vacancies for enhanced CO-SCR performance

Abstract

To further enhance the purification efficiency of NO_x, it is crucial to develop advanced CO-SCR catalysts with superior performance. In this study, MnO supports were synthesized by hydrogen reduction of K₂Mn₄O₈ and OMS-2 materials. A bimetallic Pd–Fe supported catalyst, PdFe/K-OMS-2, was prepared via the impregnation method, and its catalytic activity in the CO-SCR reaction was systematically evaluated. The results indicate that when the Pd loading is 1 wt% and the Fe loading is 3 wt%, the PdFe/K-OMS-2 catalyst demonstrates outstanding CO-SCR performance, maintaining high efficiency (≥90%) and stability at 200 °C, as well as excellent water resistance at 300 °C. Comprehensive characterization techniques reveal that, after heat treatment, Fe facilitates the transformation of OMS-2 into MnO at low temperatures, thereby enhancing the concentration of Mn²⁺, increasing the content of Pd²⁺ and oxygen vacancies, and promoting the interaction between Pd and Fe, which significantly improves the low-temperature activity of the PdFe/K-OMS-2 catalyst. Furthermore, in situ DRIFTS studies elucidated that the catalyst predominantly follows the Mars–van Krevelen (MvK) mechanism, where NO and CO are simultaneously adsorbed on the catalyst surface and subsequently react. The present doping-based approach to optimizing carrier structure fabrication provides a conceptual framework for the systematic design and synthesis of high-performance bimetallic catalysts.