Promotion effect of Ni doping on the oxygen resistance property of Fe/CeO2 catalyst for CO-SCR reaction: Activity test and mechanism investigation

Catalytic reduction of NO using CO, which is usually present in the flue gas of the iron and steel industry, is considered as an economical and eco-friendly de-NOx method (CO-SCR). However, the oxygen present in the flue gas will significantly inhibit the CO-SCR activity of the catalyst, thereby limiting its industrial application. Herein, catalysts based on iron and cerium oxides were prepared and modified with different metals to investigate their performance for the CO-SCR reaction in the presence of oxygen. The results show that the Fe/CeO2 catalyst can reach 99% NO conversion at 200 °C, but its activity decreased dramatically to 42.7% when the oxygen is present (0.5 vol%). By contrast, the NO conversion of Ni-doped Fe/CeO2 catalyst demonstrated significant enhanced oxygen resistance and could achieve 92% even at 150 °C in the presence of 0.5 vol% oxygen. Characterization techniques such as N2 adsorption, XRD, SEM/TEM, XPS, H2-TPR, and in situ DRIFT were employed to investigate the mechanism of the improved oxygen resistance property of Ni-doped catalyst. The results show that the doped Ni can interact with Fe species, increases the BET surface area of the catalyst and generates more surface oxygen vacancies (SOV) and surface synergetic oxygen vacancy (SSOV) in CO-SCR reaction, thereby improving the redox performance of the catalyst. In situ DRIFT results show that the better redox performance of NiFe/CeO2 catalyst is conducive to the conversion of adsorbed NOx species to the reactive intermediate NO2- species during the reaction. Meanwhile, the enhanced SOV/SSOV in the NiFe/CeO2 catalyst can remain active in the presence of oxygen. Therefore, the NiFe/CeO2 catalyst exhibits a promising catalytic activity in CO-SCR reaction when oxygen is present.