Fine-Tuningthe Activity Volcano of Single-Atom IronCatalysts in NH₃–SCR Regulated by Local CoordinationEnvironment

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.