A Stability Directed Dual-Filter Strategy for MOF Electrolytes to Achieve Durable High-Power PEM Water Electrolysis under Dynamic Operation

Abstract

The high current density performance of proton exchange membrane water electrolyzers (PEMWEs) is critically limited by mass transport constraints in the anode catalyst layer, where inefficient proton conduction and sluggish gas bubble removal coexist. Functional metal organic frameworks (MOFs) offer a promising pathway to address these limitations, but a fundamental gap persists: what structural characteristics guarantee both high performance and long-term durability under the harsh, oxidative conditions of the PEMWE anode? To answer this, we strategically introduce -for the first time- two structurally distinct MOFs into the anode catalyst layer in this demanding environment: IM UiO 66 AS (featuring robust Zr6 oxo clusters and hierarchical porosity) and BUT 8(Cr) (possessing a high density of sulfonic acid groups). Both materials enhance the performance and stability of the anode compared to the bare Nafion® baseline. The optimized electrode incorporating IM UiO 66 AS achieves a current density of 10.71 A cm-2 at 2.2 V (a 30% improvement) and shows a voltage decay rate three times lower over 500 hours. Although BUT 8(Cr) also outperforms the baseline, it degrades more rapidly than IM UiO 66 AS, which maintains robust stability even under dynamic, renewable-mimicking cycling. Beyond reporting two effective functional electrolyte materials, this comparative study leverages a full suite of electrochemical and physicochemical diagnostics to establish, for the first time, a clear set of material survival criteria for MOFs in PEMWE anodes. These criteria are formulated as a practical dual filter selection framework: (1) a function filter, requiring hierarchical porosity coupled with proton conducting sites; and (2) an indispensable stability filter, demanding rigid clusters of hard Lewis acidic metals (e.g., Zr4+) to ensure irreversible stability under acidic, oxidative, and hydrating conditions. This work thus moves beyond isolated material demonstrations, offering a generalizable design roadmap for developing durable, high power PEMWEs compatible with intermittent renewable energy.