Lattice modulation of bimetallic zero-valent iron to boost selective hydrodechlorination of organic pollutants

Atomic hydrogen (*H) in bimetallic nanoscale zero-valent iron (M-nFe⁰)-water system plays a dominant role for realizing in-situ deep dechlorination reactions, yet its selective generation and sustainable utilization remain challenging. Herein, a structural modulation strategy was proposed to design lattice engineered M-nFe⁰ (M-nFe⁰_lattice), which generated controllable lattice strain and strong M-Fe chemical bonds, thus steering *H generation/accumulation and achieving deep dechlorination of various organic pollutants. Compared with traditional surface nickel-modified nFe⁰ (Ni-Fe⁰_surface), the dechlorination rate of Ni-Fe⁰_lattice for TCE and 4-CP was improved by 3.6 ∼ 6.1 times, and the corresponding electron selectivity was increased from 18.2 % ∼ 23.2-48.6 % ∼ 60.3 %. Ni-Fe⁰_lattice could still trigger complete dechlorination after 10-batch experiment. Interestingly, lattice Ni not only produced numerous defect sites and induced strain effect for accelerating electron transportation in Fe⁰ core, but also provided more accessible Ni sites for proton adsorption/water disassociation. The strong Fe-Ni electronic interaction increased *H desorption energy barrier, suppressing *H recombination and promoting *H selective generation. Besides, the strong Ni-Fe chemical bonds optimized the structural compatibility, thereby enhancing the anti-oxidation and anti-corrosion properties of Ni-Fe⁰. This study presented an attractive strategy for *H selective generation, offering theoretical guidance for in-situ deep dechlorination reactions in surface water/groundwater remediation.