Even Incorporation of Nitrogen into Fe⁰ Nanoparticles as Crystalline Fe₄N for Efficient and Selective Trichloroethylene Degradation

Abstract

Surface modification of microscale Fe powder with nitrogen has emerged recently to improve the reactivity of Fe0 for dechlorination. However, it is unclear how an even incorporation of a crystalline iron nitride phase into Fe0 nanoparticles affects their physicochemical properties and performance, or if Fe0 nanoparticles with a varied nitridation degree will act differently. Here, we synthesized nitridated Fe0 nanoparticles with an even distribution of N via a sol–gel and pyrolysis method. Nitridation expanded the Fe0 lattice and provided the Fe4N species, making the materials more hydrophobic and accelerating the electron transfer, compared to un-nitridated Fe0. These properties well explain their reactivity and selectivity toward trichloroethylene (TCE). The TCE degradation rate by nitridated Fe0 (up to 4.8 × 10–2 L m–2 h–1) was much higher (up to 27-fold) than that by un-nitridated Fe0, depending on the nitridation degree. The materials maintained a high electron efficiency (87–95%) due to the greatly suppressed water reactivity (109–127 times lower than un-nitridated Fe0). Acetylene was accumulated as the major product of TCE dechlorination via β-elimination. These findings suggest that the nitridation of Fe0 nanoparticles can change the materials’ physicochemical properties, providing high reactivity and selectivity toward chlorinated contaminants for in situ groundwater remediation.

Sulfur-doped porous carbon sheets embedded with rich iron sites for 1O2 dominated peroxymonosulfate activation

“…3(d)). 45,46 It is noteworthy that the band center of graphitic/pyrrolic N in Fe-SNC-0.2 was ∼0.2 eV blue-shifted as compared to Fe-NC, meaning that the N atoms in Fe-SNC- Environmental Science: Nano Paper 0.2 are in a more reductive state, which is probably due to the close incorporation of the S atom. Moreover, it was found that Fe-SNC-0.2 had a more abundant graphitic/pyrrolic N content (12.0 at%) (Table S4 †), indicating that the type of iron salt in the precursor was crucial to the N-doped level.…”

Tailoring Fe0 Nanoparticles via Lattice Engineering for Environmental Remediation

“…18 Theoretical calculations show lattice N and P in a Fe (110) plane can provide hydrophobicity as that of lattice S. 59 Even incorporation of N into nFe 0 could improve the materials' hydrophobicity and electron transfer, providing efficient and selective trichloroethylene (TCE) degradation, despite the N being present as crystalline Fe 4 N rather than being incorporated into the Fe crystal. 56 It could be concluded that impregnating a Fe crystal lattice with nonmetal p-block elements is a promising strategy for lattice engineering of nFe 0 to tune their geometric−electronic structures and effects.…”

“…This allows the reconfiguration of the local charge density of Fe atoms (e.g., electrons are delocalized from the Fe atoms) . The altered electronic structure can induce changes in material properties, e.g., improved electrical conductivity, lowered reaction energy barriers, or increased binding energy for side reactions. − These changes can enhance their reactivity and inhibit the occurrence of side reactions.…”

Degradation of Chloroform by Zerovalent Iron: Effects of Mechanochemical Sulfidation and Nitridation on the Kinetics and Mechanism

“…We have shown that these materials can give ∼10−130 times greater rates of TCE reduction, 26,28 and others have reported similar enhance-ments with sulfidated/nitridated ZVI prepared in other ways. [29][30][31]it is not yet known if the benefits of S−N(C)−ZVI apply to other types of halocarbons, such as chlorinated alkanes, including CF. Furthermore, we have shown that the reactivity of S−N(C)−ZVI with TCE is highly dependent on the molar ratios of S/Fe ([S/Fe]) and N/Fe ([N/Fe]) used during its synthesis, 12,26,28 and it is of fundamental, as well as practical, interest to determine how these dependencies change with properties of the contaminant.…”