Generation of atomic hydrogen by Ni-Fe hydroxides: Mechanism and activity for hydrodechlorination of trichloroethylene.

• Ni-Fe hydroxides derived from the coprecipitation of Ni2+ and Fe2+ at neutral pH lead to the generation of H•. • H• effectively dechlorinate TCE producing nontoxic ethylene and ethane. • Ni-Fe hydroxides with the 3.0 Ni/Fe ratio shows the highest electron selectivity for TCE hydrodechlorination. • Density functional theory analysis revealed the hydrodechlorination mechanism. Atomic hydrogen (H•) is highly reactive for the hydrodechlorination of trichloroethylene (TCE). In this work, we found that the coprecipitation of Ni2+ and Fe2+ at neutral pH led to an unprecedented catalytic generation of H•. The generated H• effectively dechlorinate TCE to nontoxic ethylene and ethane, and Fe2+ is the only electron donor. The abundant adsorbed H• produced with a Ni/Fe ratio of 0.4 enhances hydrogen evolution reaction causing a low efficiency for hydrodechlorination. In contrast, the active absorbed H• is generated in the crystal lattice of Ni-Fe hydroxides with a Ni/Fe ratio of 3.0 causing highly efficient hydrodechlorination of TCE. This work not only reveals the mechanism of catalytic hydrodechlorination by Ni-Fe hydroxides at neutral pH, but also provides a novel approach to detoxify TCE in contaminated water using facile precipitated Ni-Fe hydroxides. [Display omitted] [ABSTRACT FROM AUTHOR]