Microscopic Mechanism of Fe 2 O 3 -Catalyzed NO Reduction during Sludge Combustion: A Density Functional Theory Study.

Systematic studies on the mechanism underlying Fe₂O₃-catalyzed NO reduction in a reducing atmosphere during sludge combustion remain limited. In this study, density functional theory was employed to investigate the adsorption properties of NH₃, CO, and NO on the α-Fe₂O₃(001) surface, and the mechanisms underlying the NH₃ and CO reduction of NO during the adsorption process. The results demonstrated that NH₃, CO, and NO chemically adsorbed on the surface Fe top site, thereby generating distinctly high adsorption energies. NO exhibited the highest adsorption energy. With regard to the catalytic mechanisms of NH₃ and CO during NO reduction, the α-Fe₂O₃(001) surface exhibited different characteristics. NH₃ reduction of NO tended to follow the Eley–Rideal (E-R) mechanism. The dissociation of -NH₂NO is the rate-determining step for the NH₃ reduction of NO. The presence of α-Fe₂O₃(001) reduced the dissociation energy barriers of NH₃ and NH₂NO, thereby catalyzing the reduction reaction. In contrast, NO dissociation was more challenging during the CO reduction of NO. The α-Fe₂O₃(001) surface reduced the dissociation barrier of the NO-NO dimer from 2.04 to 1.53 eV. Two adsorbed NO molecules first formed NO-NO dimers; these then dissociated into N₂O and atomic oxygen, thereby catalyzing the reduction reaction. [ABSTRACT FROM AUTHOR]