The pressing issues of global energy scarcity and water shortages can be substantially mitigated through the electrolysis of seawater. In this study, we synthesized a unique lamellar amorphous-crystalline heterostructure electrocatalyst by integrating the amorphous chromium hydroxide (Cr-OH) with the crystalline NiFe layered double hydroxides (NiFe LDH). The resulting Cr-OH/NiFeLDH@NF exhibited an exceptionally low oxygen evolution reaction (OER) overpotential and strong corrosion resistance. The development of the crystalline-amorphous heterointerface significantly influenced electronic coupling and enhanced electron transfer rates. Through the methanol response mechanism, it was demonstrated that the Cr-OH enhanced the catalyst’s corrosion resistance in chloride-rich environments and significantly extended its durability in seawater. Operative Raman spectroscopy confirmed that the high OER activity and corrosion resistance of Cr-OH/NiFeLDH@NF originated from the preferential oxidation of the outer Cr-OH layer, which promoted the electrochemical oxidation of Ni2+ to Ni4+, and the stable Cl− resistant environment formed by the in-situ generated and dissolved CrO42−.