A dual-balance strategy via phosphate modification on MnO2-CeO2 for NOx and chlorobenzene synergistic catalytic control

Abstract

Traditional MnO2-CeO2 (MnCe) exhibits efficient synergistic-control performance for selective catalytic reduction of NOx and chlorobenzene (CB) oxidation. However, the issues of N2O formation and chlorine-deposition remain challenges. Herein, a phosphate-modified MnCe exhibits both higher NOx and CB conversions than MnCe: N2O formation decreases by 23%, while HCl selectively increases by 10% at 300 ℃. Phosphate widens the band gap of Mn 3d of MnCe and recovers the bond length of Ce-O back to that of ceria, restricting the electrons transfer from surface cations to chlorine ions by the orbital polarization effect. Meanwhile, phosphate also provides more Brønsted and weakly Lewis acid sites, favoring CB nucleophilic substitutions rather than polychlorinated species accumulation. Both the chlorine adsorption energy and HCl formation barrier decrease after phosphate modification. This work provides a novel modulation strategy of dual-balance (reducibility vs. total acidity; Lewis vs. Brønsted) on the design of multi-pollutant control catalysts.