Tailoring NiFeS microstructure through electrodeposition for high-performance anion exchange membrane water electrolysis

Sustainable hydrogen production from anion exchange membrane (AEM) water electrolysis is an economically efficient alternative to proton exchange membrane (PEM) technology. However, conventional ionomer-based spray-coated electrodes suffer from poor conductivity and low utilization of active sites. These are primarily due to the agglomeration of ionomers with the catalyst, leading to uneven dispersion and significant catalyst active surface area blockage. A self-supported, ionomer-free NiFeS OER catalyst, synthesized via direct electrodeposition on a nickel fiber porous transport layer, is introduced here to address these limitations. The optimized NiFeS catalyst required only 300 mV as overpotential to accomplish 100 mA cm −2 , exhibiting superior charge transfer kinetics, as evidenced by a low Tafel slope of 84 mV dec −1 . The catalyst also had a significantly larger electrochemically active surface area (ECSA) than its monometallic counterparts. NiFeS-based electrolyzer in a practical AEMWE setup achieved an outstanding current density of 2.6 A cm −2 at 2.0 V, showing minimal voltage degradation over 100 h of operation at 1 A cm −2 and 60 °C, underscoring the applicability and durability of this catalyst for efficient hydrogen production. • Self-supported NiFeS catalyst avoids ionomer-induced active site blockage. • NiFeS achieves 100 mA cm −2 at 300 mV with excellent charge transfer kinetics. • Superior ECSA boosts NiFeS performance over monometallic counterparts. • NiFeS-based AEM electrolyzer sustains 2.6 A cm −2 at 2.0 V for 100+ hours.