Phosphate Modification Promotes Low-Temperature NH3-SCO over Cu/CeO2 Through Coupled Regulation of Surface Acidity and Oxygen Species

Selective catalytic oxidation of ammonia (NH3-SCO) is a promising technology for ammonia abatement. Cu/CeO2catalysts have attracted extensive attention because of their strong metal–support interaction and favorable redox properties. However, their practical application is still limited by insufficient low-temperature catalytic activity and unsatisfactory control of by-product formation. Herein, phosphate-functionalized Cu/CeO2catalysts were fabricated to regulate surface acidity and oxygen species behavior, thereby promoting low-temperature NH3-SCO activity. The optimal Acid-Cu/CeO2catalyst achieved 90% NH3conversion at 260 °C, corresponding to a 192 °C decrease in T90compared with pristine Cu/CeO2(452 °C). Kinetic analysis showed that the apparent activation energy decreased from 125.78 to 84.70 kJ mol−1after phosphoric acid modification. In addition, Acid-Cu/CeO2maintained relatively high N2selectivity and lower NOxselectivity over the tested temperature range, indicating that phosphate modification suppresses the deep oxidation of NH3to NOxby-products. Structural and surface characterization results demonstrated that Cu species remained highly dispersed on CeO2after modification, while surface phosphate species modified the local electronic environment and redistributed oxygen species. O 1s XPS and O2-TPD results revealed that phosphate modification decreased the static surface adsorbed/defect-related oxygen fraction but improved the accessibility and mobility of labile surface/subsurface or weakly bound lattice oxygen species. Py-IR and DRIFTS results further showed that phosphate modification increased Brønsted/Lewis acidity, enhanced NH3adsorption and N-H activation, and facilitated the formation and subsequent consumption of NHx/-NHO-related intermediates under reaction conditions. This work provides insights into phosphate-mediated regulation of surface acidity and oxygen mobility and offers a strategy for designing efficient low-temperature Cu/CeO2-based NH3-SCO catalysts.