Facilely Tuning the First-Shell Coordination Microenvironment in Iron Single-Atom for Fenton-like Chemistry toward Highly Efficient Wastewater Purification

Precisely identifying the atomic structures in single-atom sites and establishing authentic structure-activity relationships for single-atom catalyst (SAC) coordination are significant challenges. Here, theoretical calculations first predicted the underlying catalytic activity of Fe-N x C4-x sites with diverse first-shell coordination environments. Substituting N with C to coordinate with the central Fe atom induces an inferior Fenton-like catalytic efficiency. Then, Fe-SACs carrying three configurations (Fe-N2C2, Fe-N3C1, and Fe-N4) fabricate facilely and demonstrate that optimized coordination environments of Fe-N x C4-x significantly promote the Fenton-like catalytic activity. Specifically, the reaction rate constant increases from 0.064 to 0.318 min-1 as the coordination number of Fe-N increases from 2 to 4, slightly influencing the nonradical reaction mechanism dominated by 1O2. In-depth theoretical calculations unveil that the modulated coordination environments of Fe-SACs from Fe-N2C2 to Fe-N4 optimize the d-band electronic structures and regulate the binding strength of peroxymonosulfate on Fe-N x C4-x sites, resulting in a reduced energy barrier and enhanced Fenton-like catalytic activity. The catalytic stability and the actual hospital sewage treatment capacity also showed strong coordination dependency. This strategy of local coordination engineering offers a vivid example of modulating SACs with well-regulated coordination environments, ultimately maximizing their catalytic efficiency.

Automated summary

The catalytic activity of Fe-NxC4-x sites with different coordination environments was predicted through theoretical calculations. Substituting N with C to coordinate with Fe atom resulted in inferior Fenton-like catalytic efficiency. Three configurations of Fe-SACs (Fe-N2C2, Fe-N3C1, and Fe-N4) were fabricated and showed that optimized Fe-NxC4-x coordination environments significantly promoted Fenton-like catalytic activity. The coordination dependency of Fe-SACs was also observed in terms of catalytic stability and actual hospital sewage treatment capacity. This strategy of local coordination engineering provides an example of how to modulate SACs with well-regulated coordination environments to maximize their catalytic efficiency.