From Nanorods to Nanotubes: Morphological Reconstruction Enables Industrial−Ampere Water Oxidation

ABSTRACT NiFe−based catalysts for the oxygen evolution reaction (OER) are fundamentally constrained by an insufficient number of active sites and their limited exposure. To overcome this issue, we propose a route for transforming nanorods to nanotubes via electrochemical reconstruction, yielding well−exposed Fe−NiOOH nanoarrays featuring abundant active sites to boost ampere−level water oxidation. This unique architecture is derived from the Ostwald ripening of an Fe−rich Fe−Ni−MOF precursor, which subsequently generates highly active Fe−doped γ−NiOOH with an optimized electronic structure. The as−prepared Fe−NiOOH exhibits an extremely low overpotential of 309 mV at 1 A cm −2 with a Tafel slope of 51.4 mV dec −1 in alkaline media, alongside outstanding long−term stability for over 100 h. Furthermore, the Fe−NiOOH nanotubes are highly conducive to activating the lattice oxygen mechanism (LOM) and stabilizing the local oxygen coordination through structural irregularities, thus significantly enhancing the intrinsic catalytic activity. When assembled in an anion exchange membrane water electrolyzer, the catalyst enables the electrolyzer to achieve an industrial−level current density of 5 A cm −2 at a cell voltage of only 2.3 V. This work establishes a critical design principle for NiFe−based electrocatalysts and accelerates the commercialization of ampere−level water splitting technology.