Graphene-Nanoplatelets Supported NiFe-MOF: High-Efficient and Ultra-Stable Oxygen Electrodes for Sustained Alkaline Anion Exchange membrane water Electrolysis

Practical hydrogen production using high-efficient, low-cost, and stable oxygen electrodes are crucial for a sustainable clean energy future. Herein we report graphene-nanoplatelets supported (Ni,Fe)metal-organic framework (MOF) as a superior and ultra-durable (>1,000 h) anode for alkaline water electrolysis. The MOF on carbon-fiber paper electrodes requires an overpotential η=220 mV to achieve a current-density j=10 mA cm−2 (η=180 mV on nickel foam for j=20 mA cm−2) with a Tafel slope (51 mV/decade), high turnover frequency (TOF: 1.22 s−1), high Faradaic efficiency (99.1%), and long-term durability of > 1000 h on continuous electrolysis. In alkaline anion exchange membrane water electrolyzer (AAEMWE), it exhibits a record current density of 540 mA cm-2 at 1.85 V at 70 ℃, outperforming the state-of-the-art Pt/C//IrO2. A break-through strategy introduced in membrane electrode assembly(MEA) fabrication by extending the electrical contact with an aqueous electrolyte offers an additional OH‒ transport pathway to regenerate the original conductivity of the AAEMWE on continuous electrolysis, without any significant change on the pH of the electrolyte. These findings open up durable, high-performance AAEMWE and direct solar-to-fuels conversion, especially to replace high-cost proton exchange membrane (PEM) water electrolysis that already works with ultra-pure water.