The effect of phosphorus modification and sequential acidification on the NH3-SCR performance of composite metal oxide catalysts

This study investigated the effects of sequential acid treatment and phosphorus incorporation on the performance of Fe–Mn-Ce composite metal oxide catalysts. The FeMnCeO_x catalyst was prepared using the sol–gel method and modified through two methods: treatment with phosphoric acid alone and a sequential treatment with phosphoric acid followed by sulfuric acid. The results show that the sequentially acid-treated catalyst exhibited over 90% NO_x conversion and N₂ selectivity in the temperature range of 200–350 °C, outperforming other catalysts. Characterization analyses such as XRD and NH₃-TPD revealed that acid modification enhanced the surface acidity and redox properties of catalysts. XPS analysis showed that sequential acid treatment increased the surface chemisorbed oxygen content of the catalyst and optimized its surface structure. In-situ DRIFTS spectroscopy further elucidated that the catalytic reaction follows both Langmuir–Hinshelwood and Eley–Rideal mechanisms concurrently.