Crystalline-amorphous interface of mesoporous Ni2P @ FePOxHy 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 Ni 2 P @ FePO x H 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 – IrO 2 catalyst. • Noble-metal free catalysts for oxygen evolution reactions are investigated. • Crystalline (Ni 2 P) and amorphous (FePO x H y ) phases in Ni 2 P @ FePO x H y catalyst provide more electrocatalytic active sites. • The Ni 2 P @ FePO x H y catalyst shows excellent AAEMWE cell performance with a low overpotential and good stability. • The Ni 2 P @ FePO x H y catalyst exhibits a low overpotential of 360 mV for OER to deliver a high current density of 1 A cm −2 .