Understanding the roles of copper dopant and oxygen vacancy in promoting nitrogen oxides removal over iron-based...

In this work, we proposed a novel strategy of copper (Cu) doping to enhance the nitrogen oxides (NO_x) removal efficiency of iron (Fe)-based catalysts at low temperature through a simple citric acid mixing method, which is critical for its practical application. The doping of Cu significantly improves the deNO_x performance of Fe-based catalysts below 200 °C, and the optimal catalyst is (Cu_0.22Fe_1.78)_1-δO₃, which deNO_x efficiency can reach 100% at 160-240 °C. From the macro aspects, the main reasons for the excellent catalytic activity of the (Cu_0.22Fe_1.78)_1-δO₃ catalyst are the large number of oxygen vacancies (O_vac), appropriate Fe³⁺ and Cu²⁺ contents, stronger surface acidity and redox ability. From the micro aspects, the O_vac plays a key role in enhancing molecular adsorption, oxidation, and the deNO_x reaction over the Fe-based catalyst surface, which promoting order is CuO_vac > O_vac > Cu. This work provides a new insight for the mechanism study of oxygen vacancy engineering and also accelerates the development of CuFe bimetal composite catalysts at low temperature.