Fine-Tuning the Activity Volcano of Single-Atom Iron Catalysts in NH₃–SCR Regulated by Local Coordination Environment

Although advanced single-atom catalysts (SACs) have demonstrated remarkable performance in various catalytic fields, their application in selective catalytic reduction with ammonia (NH3–SCR) remains challenging due to the lack of fundamental theoretical guidance. To address this, we propose a strategy for regulating the local coordination environment by modulating the coordination of nonmetal elements around the metal center, aiming to fine-tune the catalytic activity of SACs for NH3–SCR. In this study, seven theoretical models of single-atom iron catalysts anchored on double-vacancy graphene substrates doped with three nitrogen atoms and one nonmetal atom (Fe–N3X, X = B, C, N, O, S, P, Cl) are constructed. The reaction pathways of these Fe–N3X catalysts in NH3–SCR have been systematically investigated. The activity volcano map of NH3–SCR based on the NO2 adsorption energy is established, and the catalytic activities of 30 different SACs are evaluated. Regulating the local coordination environment of the single-atom iron catalyst can fine-tune the active volcano map of the catalyst in a small range (activity, −0.7 to −1.6), while changing the active center can roughly regulate the volcano map in a wide range (activity, −0.8 to −3.5). Based on this fine-tuning strategy, we successfully improve the catalytic activities of single-atom Zn and Mn catalysts by modulating the types of coordinated nonmetal atoms. Furthermore, a linear relationship between charge transfer and NO2 adsorption energy is established, providing insights into the origin of the activity fine-tuning strategy at the electronic structure level. This work provides a novel approach to catalyst activity regulation and offers valuable guidance for designing advanced NH3–SCR catalysts.