Noble-metal free Ce-Fe-Zr ternary oxides with synergistic dual active sites for accelerating NO reduction

Abstract

Efficient NOx elimination is crucial for the control of air pollution but highly depends on the construction of active sites for both N–O bond activation and oxygen transfer. In this study, dual active sites were established in a highly-efficient Ce-Fe-Zr ternary catalyst in the one-step flame spray pyrolysis (FSP) method. We demonstrated that a large amount of Fe2+ species were formed and enriched on the surface of oxides, accompanied by the improvement of oxygen storage and release by Fe doping into CeO2 lattice at a limit-breaking level. Their synergistic effect greatly enhanced the kinetics of the NO reduction step, which was attributed to the activation of NO on Fe2+ active site in the form of Fe2+-(NO)2 intermediate as well as the acceleration of the oxygen transfer through the adjacent oxygen vacancies. As a result, almost 100 % NO conversion was achieved at 175 °C, and they completely transferred into N2 at low temperature (223 °C) without noble metals. The development of flame technology here will provide an efficient way for the fabrication of multi-active sites in a metastable structure, exhibiting great potential in rational catalyst design.