A combined DFT and experimental study of NO by NH3-selective catalytic reduction over an Fe-doped CoAl2O4 catalyst

Abstract

The selective catalytic reduction of NO_x by NH₃ (NH₃-SCR) has garnered significant attention. However, the industrial application of the catalysts is limited due to their poor low-temperature activity and narrow operation window. In this study, we have elucidated that Fe doping significantly improves the low-temperature NH₃-SCR activity of CoAl₂O₄ catalysts at the atomic level by means of density functional theory calculations and experimental measurements. The structures of the low-refractive index (100) surface of both intrinsic CoAl₂O₄ and Fe-doped CoAl₂O₄ catalysts, as well as the adsorption models for molecules such as NH_3, were computationally determined. In addition, the reaction process of NO_x removal by NH₃ was investigated thoroughly. The results showed that the adsorption energy of NH₃ increased after Fe doping. It is noteworthy that the doped Fe site is also a strong active site for the catalytic reaction. Moreover, the first dehydrogenation step of NH₃ is a rate-determining step (0.82 eV), and Fe doping also significantly reduces the NH₃-SCR reaction path energy barrier (0.67 eV). Intrinsic CoAl₂O₄ and Fe-doped Fe-CoAl₂O₄ catalysts were prepared by hydrothermal and impregnation methods. The results showed that the Fe doped CoAl₂O₄ catalyst could significantly enhance its denitrification catalytic activity, thereby indicating the excellent selectivity of the Fe-CoAl₂O₄ catalyst, which is consistent with the calculated results. The present study presents a novel approach to enhance the catalytic efficiency of CoAl₂O₄ denitrification, thereby facilitating the development of CoAl₂O₄ spinel-based catalysts with superior performance.