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

• Comparable performance to noble metals was achieved for Ce-Fe-Zr oxides. • Completely NO conversion to N 2 was realized at 223°C without PGMs. • Dual active sites were established in one-step by FSP technology for TWCs. • FSP method is promising in breaking the limitation of dopants in oxide lattice. • FSP assisted Fe dopant dominated in NO activation and active oxygen transfer. Efficient NO x 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 Fe 2+ species were formed and enriched on the surface of oxides, accompanied by the improvement of oxygen storage and release by Fe doping into CeO 2 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 Fe 2+ active site in the form of Fe 2+ -(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 N 2 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.