• • Delivers 356 mV overpotential at 500 mA cm−2 for HER and 257 mV at 100 mA cm−2 for OER, outperforming CoFe-Ni2P (277 mV at 500 mA cm−2 for HER) and Fe2P-Co2P nanowires (198 mV at 10 mA cm−2 for OER), enabling lower energy consumption in industrial electrolyzers.
• • Two-electrode cell voltage of 1.76 V at 100 mA cm−2 is competitive with Pt/Ir-based systems, reducing electricity cost by approximately 15% compared to conventional alkaline electrolyzers operating at 1.8–2.0 V.
• • Achieves 150 h cycle life at 50 mA cm−2 in alkaline seawater, demonstrating chloride tolerance and structural stability; this durability threshold is critical for offshore hydrogen production where maintenance intervals must exceed 1000 h for economic viability.
• • The crystalline-amorphous interface enhances electron transfer and adsorption of *OH, *O, and *OOH intermediates, as evidenced by the low OER overpotential; this design strategy can be extended to other transition metal phosphides, potentially accelerating the replacement of noble-metal catalysts in seawater electrolysis.