Trimetallic FeNiCu Atomic Clusters Supported on Carbon Matrix: Highly Active Catalysts for CH-SCR of NO.

CH-SCR denitrification technology faces catalyst deactivation problems and low catalytic performance at medium-low temperatures. This study utilized the intermetallic synergies to prepare atomic cluster catalysts (FeNiCu/NC) by anchoring Fe-Ni-Cu on a carbon matrix to enhance the CH-SCR performance at medium-low temperatures. The synergistic effect of the Fe-Ni-Cu is reflected in the differences in the physicochemical properties of the catalysts, which is proved by several characterization techniques. Results showed that the FeNiCu/NC catalyst had a larger surface area (541.4 m/g) and there were no metal oxides on the surface of the catalyst but abundant defective sites that anchored Fe/Ni/Cu atoms through N atoms to form M-N active sites and atomic clusters. The hollow carbon morphology provides sufficient active sites for CH-SCR. The coordination environments of active sites were M-N-C, Fe/FeCu/FeNi, Ni/NiFe/NiCu, and Cu/CuFe/CuNi, where the synergistic action of trimetal leads to the presence of Fe-Ni-Cu-N-C. The synergistic action of the Fe-Ni-Cu significantly improved the CH-SCR performance at medium-low temperatures. The FeNiCu/NC exhibited an 81% NO conversion at 150 °C under 2% O, 15% and 20% higher than FeNi/NC and FeCu/NC catalysts, respectively. Even at 4% O, the FeNiCu/NC catalyst was active to remove 78% NO and achieve a 93% N selectivity at 150 °C and maintained a 100% NO conversion at 300-425 °C. The DRIFTS results demonstrated that NO and CH could combine with active O at metal cluster, M-N, or defective oxygen sites to produce various intermediate species, wherein acetates and nitrates were the main active intermediates. Based on the DRIFTS results, a reaction pathway for CH-SCR over the FeNiCu/NC catalyst was proposed.