Probing into the Catalytic Activity of Single-Atom Catalysts for NO Oxidation by H2O2 via the Tri-activity Volcano Plot

The recently emerging single-atom catalysts (SACs) are proposed as promising candidates for the catalytic oxidation of NO in the field of NO pollutant reduction from coal-fired power stations. However, due to the lack of theoretical model guidance, achieving efficient catalytic oxidation of NO at room temperature still remains a major concern. Thus, in this study, the reaction pathways for the catalytic oxidation of NO by OOH radicals on eight TM–N₄–C (TM = Sc, Cr, Mn, Fe, Co, Ni, Cu, and Zn) were investigated based on density functional theory calculations. Based on the Bronsted–Evans–Polanyi linear relationship and microkinetic simulations, the activity volcano plot model for the catalytic oxidation of NO by OOH has been successfully established and validated. The Fe–N₄–C and Mn–N₄–C catalysts showed higher reactivities among these catalysts. The energy barriers for the rate-determining steps of these two catalysts were 0.14 and 0.30 eV, respectively, illustrating that catalytic oxidation of NO is feasible at room temperature. Significantly, a tri-activity volcano plot was constructed based on the unified activity descriptor of O adsorption energy for guiding the design of SACs in H₂O₂ catalytic oxidation of NO. The pathway of catalytic oxidation NO by OOH radicals is the dominant route in the system of SACs for the catalytic oxidation of NO by H₂O₂. The analysis of Bader charge and electronegativity revealed a linear correlation between the structural properties of the catalysts and the catalytic activity descriptor, which can be used to quickly predict the reactivity of SACs with different coordination environments. This work provides a new pathway for the current NO oxidation and guides future work on catalyst screening and experimental preparation.