Even Incorporation of Nitrogen into Fe 0 Nanoparticles as Crystalline Fe 4 N for Efficient and Selective Trichloroethylene Degradation.

Surface modification of microscale Fe powder with nitrogen has emerged recently to improve the reactivity of Fe 0 for dechlorination. However, it is unclear how an even incorporation of a crystalline iron nitride phase into Fe 0 nanoparticles affects their physicochemical properties and performance, or if Fe 0 nanoparticles with a varied nitridation degree will act differently. Here, we synthesized nitridated Fe 0 nanoparticles with an even distribution of N via a sol-gel and pyrolysis method. Nitridation expanded the Fe 0 lattice and provided the Fe 4 N species, making the materials more hydrophobic and accelerating the electron transfer, compared to un-nitridated Fe 0 . These properties well explain their reactivity and selectivity toward trichloroethylene (TCE). The TCE degradation rate by nitridated Fe 0 (up to 4.8 × 10 -2 L m -2 h -1 ) was much higher (up to 27-fold) than that by un-nitridated Fe 0 , 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 Fe 0 ). Acetylene was accumulated as the major product of TCE dechlorination via β-elimination. These findings suggest that the nitridation of Fe 0 nanoparticles can change the materials' physicochemical properties, providing high reactivity and selectivity toward chlorinated contaminants for in situ groundwater remediation.