Boosting NH₃–SCR Activity and Hydrothermal Stability of Fe–Cu/β Catalysts via Barium Promotion

Fe–Cu/β catalysts face severe industrial adoption barriers in NH3–SCR systems primarily due to an insufficiently broad operational temperature range and structural instability under hydrothermal conditions. In this study, barium modification was employed to concurrently broaden the active temperature range and enhance structural robustness. By integration of Ba into Fe–Cu/β via ion exchange, the catalyst exerted negligible effects on textural properties (N2 physisorption/XRD/TEM). Synergistic Ba–Fe/Cu interactions enhance dispersion (EDS/UV–vis DRS) and redox properties (H2-TPR/XPS), which promote the formation of more highly dispersed Fe/Cu species. Despite reduced Brønsted/Lewis acidity at medium-to-high temperatures (NH3-TPD/in situ DRIFTS), sufficient acid sites across the whole temperature range and redox capacity ensured superior activity, expanding the T90 window to 195 to above 525 °C (vs 210–500 °C for Fe–Cu/β). After high-temperature hydrothermal treatment at 650 °C for 100 h, barium mitigated structural degradation (11.8% higher surface area, 12.9% larger pore volume, and lower loss of crystallinity) by stabilizing Si–O–Al bonds and anchoring Fe/Cu species (TEM/EDS/UV–vis DRS), which preserved redox functionality and acidity. Consequently, aged Ba-modified Fe–Cu/β maintained a lower T80 threshold (≥245 °C vs ≥450 °C for Fe–Cu/β) and reduced N2O emissions via the suppression of Cu aggregation. In situ DRIFTS measurements revealed that the SCR reaction over Fe–Cu/β and Ba-doped Fe–Cu/β catalysts conformed to both the E-R and L-H mechanisms simultaneously. This study demonstrates that barium modification effectively addresses the limitations of a narrow temperature window and poor hydrothermal stability in Fe–Cu/β catalysts, offering a viable strategy for advanced SCR systems.