Al-mediated surface-oxygen and textural regulation in Fe-Cu-Al oxides for broad-temperature NH₃-SCR and gas-phase Hg⁰...

Deep flue-gas purification requires catalysts capable of simultaneously removing NO_x and Hg⁰ under humid, sulfur-containing conditions. Fe-Cu-Al ternary oxides (Fe_0.1Cu_0.06Al_x) were prepared by a citrate-assisted sol-gel route and evaluated for NH₃-SCR and gas-phase Hg⁰ removal. Fe_0.1Cu_0.06Al_0.02 achieved 99.7-99.9% NO conversion and 95.5-98.9% Hg⁰ removal over 200-400 °C, while maintaining approximately 91-99% N₂ selectivity over 100-400 °C. At 250 °C, high activity was retained in 8 vol% H₂O and 200 ppm SO₂, with substantial recovery after removing the co-feeds. EPR and XPS showed the strongest g = 2.003 vacancy-related signal and the highest fresh-sample O_α fraction of 60.38%. Fresh/used XPS indicated moderate surface-state evolution while the principal fitted components remained detectable. Representative DFT models predicted that the initial NH₃ dehydrogenation energy decreased from 3.39 to 1.77 eV, while SO₂ adsorption weakened from -2.90 to -2.29 eV and Bader charge redistribution decreased from + 0.213 to + 0.159 |e| after Al substitution. DRIFTS and DFT were consistent with an L-H-type contribution but did not establish a unique pathway or atomistic vacancy structure. XRD, EDS, and BET suggest a partial textural-promoter role for nano-Al₂O₃, although its local environment remains unresolved.