Phosphate-Modified and Fe-Doped Highly Crystalline β-Ni(OH) ₂ for Durable Oxygen Evolution at Industrial Current Densities

Durable oxygen evolution reaction (OER) catalysts that operate at industrial current densities are vital for practical alkaline and seawater electrolysis but remain rare due to the intrinsic trade-off between phase stability and conductivity in Ni-based systems. Here, we introduce a synergistic phase–electron–interface design. This strategy integrates Fe3+ doping and phosphate (PO43–) interface modification within highly crystalline β-Ni(OH)2 nanosheet arrays grown in situ on Ni foam. The resulting three-dimensional (3D) phosphate-modified electrode, denoted Pi-FeNi(OH)2/NF, delivers an overpotential of 447 mV at 1000 mA cm–2 in 1 M KOH and operates stably for ≥170 h with negligible decay in simulated seawater. Density functional theory reveals preferred PO43– binding at Fe sites (0.92 eV, 0.07 eV lower than Ni), with Fe3+–PO43– coupling shifting the Ni d-band center to −1.72 eV, enriching Fe 3d states, optimizing oxygen intermediate energetics, and lowering the rate-determining step barrier to 2.11 eV. In situ Raman, XPS, XANES/EXAFS, and EIS validate that high crystallinity, electronic modulation, and tailored interfacial chemistry collectively underpin the exceptional stability and activity. This work establishes a scalable β-Ni(OH)2 platform that unites structural robustness with high-efficiency OER, offering a blueprint for next-generation industrial electrolyzers.