In Situ Self‐Assembled 200 nm‐Depth Highly Active Layer Non‐Precious Metals Catalyst for Industrial Water Electrolysis

Abstract Nickel‐based electrocatalysts are promising for industrial water electrolysis, but the dense hydroxyl oxide layer formed during the oxygen evolution reaction (OER) limits active sites accessibility and presents challenges in balancing structural stability with effective charge transfer. Based on this, an efficient in situ leaching strategy is proposed to construct grain boundary‐rich catalyst structure with high charge transfer ability and a deep catalytic active layer reached >200‐nm. Under OER conditions, stable sub‐nano Ni ₃ Al particles are embedded in Ni(Fe)OOH, originating from leaching out the unstable Ni ₂ Al ₃ phase of the initial Ni ₂ Al ₃ /Ni ₃ Al alloy doped with Fe. The structural evolutions are characterized using in situ Raman spectroscopy, transmission electron microscopy, and X‐ray absorption spectroscopy. The catalyst exhibits exemplary performance, evidenced by a low overpotential of 212 mV at 10 mA cm ⁻² , a minimal Tafel slope of 25.0 mV dec ⁻¹ . The catalyst maintains stable for >500 h at 500 mA cm ⁻² under industrial conditions. Furthermore, its performance in seawater electrolysis is notably superior, exhibiting an overpotential of 223 mV at 10 mA cm ⁻² and a Tafel slope of 37.5 mV dec ⁻¹ . The in situ high activity in the deep porous phase by leaching out unstable phases provides a new method for engineering high‐performance industrial catalysts.