Regulation of bulk reconstruction of FeNiMoO 4 via NH 3 treatment for high performance water oxidation

The self-reconstruction of Ni-based electrodes and the in situ generation of oxy-hydroxides are widely investigated as crucial prerequisites for efficient oxygen evolution reaction (OER). However, the transformation is usually time-consuming and surface-limited, resulting in insufficient active sites with unsatisfactory intrinsic activity. Herein, we provide a NH 3 -treated Fe-doped NiMoO 4 hydrate as a highly active OER pre-catalyst, with an overpotential of only 240 mV at 100 mA cm −2 and 270 mV at 300 mA cm −2 . By combination of multiple quasi-situ and in situ techniques, the enhanced performance is ascribed to the lattice distortion in the pre-catalyst induced by the NH 3 treatment. Firstly, the lattice defects with tensile strain and voids accelerate the selective dissolution of MoO 4 2− and ensure the rapid and bulk reconstruction of the pre-catalyst with enriched active sites. Moreover, it could modulate the electronic structure and optimize the synergism between Ni and Fe, facilitating the dynamic evolution of Fe-doped γ-NiOOH (γ-Ni(Fe)OOH). The intimately interacted Ni–Fe dual-sites from γ-Ni(Fe)OOH and the resultant distorted structure facilitate the formation and adsorption of active oxygen species, accounting for the improved intrinsic activity for OER.