Hierarchical structured Ti-doped CeO2 stabilized CoMn2O4 for enhancing the low-temperature NH3-SCR performance within highly H2O and SO2 resistance
Developing effective and stable catalysts for low-temperature selective catalytic reduction (SCR) of NO x remains challenging. Herein, we constructed a hierarchical structure by loading CoMn 2 O 4 onto Ti-doped CeO 2 , that CoMn 2 O 4 /CeTiO x catalyst has shown superior deNO x activity (>95% at 100–225 °C), prominent reaction activation energy (28.8 ± 0.9 kJ mol −1 ) and outstanding stability (>75% at 100–200 °C within H 2 O and SO 2 ). The “low-temperature active sites” and “dual anti-poisoning sites” contribute to excellent activity and stability. Firstly, the hierarchical structure boosts generation of active metal-support interface, which is conducive to oxygen migration (including adsorbed oxygen (O ads ), lattice oxygen (O lat ) and oxygen vacancy (O v )) and metal charge transfer (Mn 2+/3+ +Ce 4+ ↔Mn 3+/4+ +Ce 3+ , Ti 4+ +Ce 3+ ↔Ce 4+ +Ti 3+ ). This is the key to breaking through the limits of catalytic activity stability. Secondly, enhanced surface acidity favors NH 3 adsorption and activation, which accelerates -NH 2 /-NH concatenate with NO x through Eley-Rideal mechanism to generate N 2 and H 2 O. Thirdly, the dual strong SO 2 affinity sites by Ti-induced CeO 2 crystal reconstruction retard the active center affected by the sulfate species, which contributes to striking stability. This work highlights the importance of design of isolated active sites to improve SO 2 and H 2 O endurance.
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