Axial coordination tuning Fe single-atom catalysts for boosting H₂O₂ activation

Precisely regulating the coordination microenvironment of single-atom catalysts (SACs) to achieve enhanced reactivity is significant and desired but still in its infancy. Herein, a coordination-tuned and pyrolysis-free strategy is reported for the fabrication of a Fenton-like SAC containing the axial five-coordinated configuration (Fe–N₅). The N species on the N-doped graphene act as anchoring points for iron phthalocyanine (a typical Fe–N₄ complex) to obtain isolated Fe–N₅ sites, which significantly modulates the electronic state of Fe atoms and lowers the H₂O₂ activation barrier for •OH production. Moreover, the enriched pyridinic N serve as contaminant adsorption sites shortening •OH diffusion distance, establishing a dual-site reaction mechanism with Fe–N₅ sites. As such, the Fe–N₅ catalyst exhibits exceptional Fenton activity towards catalytic oxidation of phenol (k = 0.180 min⁻¹). Our work unravels the dependence of Fenton activity on the single-atom coordination environment and provides a platform for precise engineering of SACs.