Integrative Lattice and Surface Engineering of Nanoscale Fe for Superior Dechlorination of Trichloroethene in Groundwater: Coordination in Reactivity, Selectivity, and Stability.

Nanoscale zero-valent iron (nFe) materials hold great promise in environmental remediation, yet achieving high reactivity, selectivity, and stability in reduction remains a long-standing challenge. Here we address this challenge by employing Ni lattice and FeS surface engineering to fabricate novel nFe-based nanomaterials (dubbed as FeNi@FeS), featuring FeNi as the core and FeS as the shell. The FeNi@FeS delivered approximately 242.7- and 81.2-times higher reactivity and selectivity, respectively, over unmodified nFe° for the remediation of trichloroethene (TCE; a notorious environmental pollutant), while maintaining high stability in groundwater remediation. We found that the core composition (i.e., Ni/Fe ratio) of FeNi@FeS primarily determined reactivity, governed by a tradeoff between the galvanic effect and lattice strain, while shell properties mainly controlled selectivity, despite some interactions between them. Density functional theory (DFT) calculations revealed that the FeS surface served as a favorable adsorption site for TCE, and the low energy barriers (TS2, 0.19 eV) of FeNi@FeS facilitated the cleavage of the first chlorine from TCE. Moreover, the core-shell structure promoted electron transfer from the core to the shell and TCE. This integrative lattice and surface engineering strategy provides a new avenue for designing advanced functional materials for environmental remediation and beyond.