Self-supported crystalline-amorphous composites of metal phosphate and NiS for high-performance water electrolysis under industrial conditions

Abstract

Developing affordable and efficient electrocatalysts toward water electrolysis under industrial conditions is crucial for large-scale production of green hydrogen. In this regard, we propose a facile and mild method to construct crystalline-amorphous composites of metal phosphate (MPi) and NiS on nickel foam (NF) for practical water electrolysis. The as-prepared electrodes exhibit excellent performance, achieving a remarkable current density of 1000 mA cm–2 at the ultralow overpotential of 345 and 223 mV for FePi-NiS/NF (oxygen evolution reaction, OER) and NiCoPi-NiS/NF (hydrogen evolution reaction, HER), respectively. The composites can undergo an in-situ transformation into highly active and targeted species under high current density, which possess a unique pore structure interconnected by nanosheets that provides an abundance of catalytic sites and open channels for efficient bubble diffusion. When operated under industrial conditions (6 M KOH, 70 °C), the assembled electrode requires only 1.712 V to attain a current density of 1000 mA cm−2. The electrodes also demonstrate exceptional performance in alkaline electrolysis with an anion exchange membrane (AEMWE) when scaled up to a larger size (area: ≈ 25 cm2). Specifically, they achieve a substantial current of 12.5 A at 1.87 V with a high energy efficiency of 79.2 % and remarkable durability over 30 h under industrial electrolysis conditions (1 M KOH, 50 °C), outperforming benchmark Pt/C/NF || IrO2/NF electrodes with energy saving of 0.215 kWh Nm–3. This work provides a cost-effective and efficient strategy for designing and constructing stable and active catalysts for water electrolysis under harsh industrial conditions.