Crystalline-amorphous interface of mesoporous Ni₂P @ FePO_xH_y for oxygen evolution at high current density in alkaline-anion-exchange-membrane water-electrolyzer

For industrial high-purity hydrogen production, it is essential to develop low-cost, earth-abundant, highly-efficient, and stable electrocatalysts which deliver high current density (j) at low overpotential (η) for oxygen evolution reaction (OER). Herein, we report an active mesoporous Ni₂P @ FePO_xH_y pre-electrocatalyst, which delivers high j = 1 A cm⁻² at η = 360 mV in 1 M KOH with long-term durability (12 days), fulfilling all the desirable commercial criteria for OER. The electrocatalyst shows abundant interfaces between crystalline metal phosphide and amorphous phosphorus-doped metal-oxide, improving charge transfer capability and providing access to rich electroactive sites. Combined with an excellent non-noble metal-based HER catalyst, we achieve commercially required j = 500/1000 mA cm⁻² at 1.65/1.715 V for full water-splitting with excellent stability in highly corrosive alkaline environment (30% KOH). The alkaline-anion-exchange-membrane water-electrolyzer (AAEMWE) fabricated for commercial viability exhibits high j of 1 A cm⁻² at 1.84 V with long-term durability as an economical hydrogen production method, outperforming the state-of-the-art Pt/C–IrO₂ catalyst.