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

Abstract

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.

Atomically Dispersed p‐Block Aluminum‐Based Catalysts for Oxygen Reduction Reaction

“…Raman spectra of Al‐N‐C‐T (Figure S5) display two distinct carbon structure peaks centered at ~1370 cm −1 and 1590 cm −1 , corresponding to the disorder carbon matrix (D band) and graphitic carbon plane (G band) [16] . The ratio of D and G peak intensity ( I D / I G ) slightly decreases with annealing temperature which agrees well with the previous reports [17] . The BET surface area and pore volume were also tested for the Al‐N‐C‐T catalysts (Figure S6).…”

Atomically Dispersed p‐Block Aluminum‐Based Catalysts for Oxygen Reduction Reaction

“…[16] The ratio of D and G peak intensity (I D /I G ) slightly decreases with annealing temperature which agrees well with the previous reports. [17] The BET surface area and pore volume were also tested for the Al-N-C-T catalysts (Figure S6). Along with the increasement of pyrolysis temperature, the BET surface area and pore volume of Al-N-C-T catalysts become larger.…”

Breaking the Symmetry of Nitrogen‐Coordinated Single‐Atom Catalysts for Advanced Peroxymonosulfate Oxidation

“…The electronegativity of S (χ=2.58) is similar to that of C (χ=2.55), the C,N co‐coordinated iron‐based SACs (Fe−N 2 C 2 ) was synthesized by high‐temperature calcination of ferric chloride, urea, ammonium chloride, ammonium molybdate and pyromellitic dianhydride, which displayed excellent performance for As(III) detection [10] . In PMS−AOPs, the substitution of C atoms caused the d‐band center of Fe shifting negatively away from the Fermi level, which reduced PMS adsorption, and thus the catalysts with C instead of N coordinated to the central Fe atom had inferior Fenton‐like catalytic activity [3c] . Different from C, the sizes of S and N atoms do not match.…”