Heterojunction structures improve the intrinsic activity of electrocatalysts by enhancing the charge transfer between the catalyst and the electrode. In this paper, the NiS/FeS₂ heterostructured electrocatalyst is fabricated by a simple sulfidation method using an interface engineering strategy to adjust the surface electron density of the electrocatalyst. As expected, NiS/FeS₂ electrocatalyst exhibits superior activity and durable oxygen evolution reaction (OER) stability, requiring only a low overpotential of 183 mV to achieve a current density of 10 mA·cm⁻² and can be stable for more than 80 h, superior to NiS, FeS₂ electrocatalyst individually, and precious RuO₂. Notably, NiS/FeS₂ is also a good bifunctional electrocatalyst with good overall water splitting performance, and it only requires a voltage 1.56 V to obtain a current density of 10 mA·cm⁻² for more than 12 h. Remarkably, the NiS/FeS₂ hybridization facilitates the formation of coral-like structures, increasing the electrochemical surface area (ECSA) and enhancing the charge transfer efficiency, thus leading to excellent electrocatalytic performance. This work proposes a constructive strategy for designing efficient electrocatalysts based on interface engineering, and lays a foundation for designing a new class of electrocatalysts.

Water electrolysis is severely impeded by the kinetically sluggish oxygen evolution reaction (OER) due to its inherent multistep four-electron transfer mechanism. However, designing advanced OER electrocatalysts with abundant active sites, robust stability, and low cost remains a huge challenge. Herein, a facile and versatile multiscale manipulating strategy was proposed to construct a novel V-NiFe₂O₄@Ni₂P heterostructure self-supported on Ni foam (V-NiFe₂O₄@Ni₂P/NF). In such unique architecture, the intrinsic OER catalytic activity was greatly boosted by the in-situ generated heterogeneous Ni₂P phase induced by precisely selective phosphorylation of the NiFe-precursor, while the synchronous metal V doping stimulated the activity via modulating the electronic configuration, thus synergistically promoting its OER kinetics. In addition, the binder-free catalyst built from three-dimensional (3D) nanosheet arrays (NSs) can offer a large active surface for efficient charge/mass transfer and a robust scaffold for the integrated structure. The as-prepared flexible electrode exhibited superior OER activity with an ultra-low overpotential of 230 mV at 50 mA·cm⁻² and outstanding long-term stability for 40 h. This discovery is expected to provide an opportunity to explore efficient and stable commercial materials for scalable, efficient, and robust electrochemical hydrogen (H₂) production.