Calcium poisoning mechanism on the selective catalytic reduction of NO by ammonia over the γ-FeO (001) surface.

γ-FeO has an excellent low-temperature selective catalytic reduction (SCR) deNO performance, but its resistance to alkaline earth metal calcium (Ca) is poor. In particular, the detailed mechanism of Ca poisoning on the γ-FeO catalyst at the atomic level is not clear. Hence, the density functional theory method was used in this research to investigate the influence mechanism of Ca poisoning on the NH-SCR over the γ-FeO catalyst surface. The findings reveal that NH, NO, and O molecules can bind to the γ-FeO (001) surface to generate coordinated ammonia, monodentate nitroso, and adsorption oxygen species, respectively. The main active site is Fe-top. For the γ-FeO with Ca poisoning, the Ca atom has a high adsorption energy on the surface of γ-FeO (001), which covers the catalyst surface and reduces the active sites. The presence of Ca atom decreases the adsorption performance of NH, while slightly improving the NO and O adsorption. In particular, the Ca atom restrains the NH activation and NH formation, which is detrimental to the NH-SCR process.