Low-crystallinity Ni(OH)2/FeOOH heterojunction with in-situ surface reconstruction for accelerated oxygen evolution

Exploiting low-crystallinity as a structural feature offers a powerful route to unlock new catalytic functionalities by maximizing defect density, tuning electronic structures, and facilitating rapid charge transfer. Moreover, the disordered catalysts are prone to electrochemical reconstruction, generating highly active oxyhydroxide species, thus promoting the catalytic activity. Here, we first prepare a low-crystallinity Ni(OH) 2 /FeOOH heterojunction pre-catalyst directly grown on nickel foam via electrodeposition, followed by electrochemical reconstruction to synthesize the final electrocatalyst with surface-enriched Ni-Fe oxyhydroxide species (ER-Ni(OH) 2 /FeOOH). The defect-rich structure synergistically couples Ni and Fe species, enabling an exceptionally low overpotential of 241 mV at 100 mA cm −2 for the alkaline oxygen evolution reaction (OER), while maintaining stable operation for over 40 h. The density functional theory (DFT) calculations confirm that the low-crystallinity heterointerface tunes the electronic structure and lowers the energy barrier for the rate-determining (RDS) *OH→*O step, thus providing a theoretical basis for the observed enhancement in OER activity. This work underscores the potential of low-crystallinity interface engineering as a powerful approach for constructing next-generation OER catalysts.