Interfacial engineering of Mo-doped Ni3S2/FeNi2S4 heterostructures for durable industrial level-current-density AEM water electrolysis

Abstract

Developing efficient non-noble-metal-based electrocatalysts is vital for cost-effective energy conversion technologies. Anion exchange membrane water electrolyzers (AEMWEs) are emerging as a promising platform for green hydrogen production due to their ability to operate in alkaline media with low-cost catalyst materials. In this study, we designed and synthesized a Mo-doped Ni₃S₂/FeNi₂S₄ hybrid nanocomposite as a high-performance oxygen evolution reaction (OER) anode for AEMWE. Experimental and theoretical analyses reveal that Mo incorporation into the Ni₃S₂/FeNi₂S₄ hybrid triggers interfacial charge redistribution, optimizing hydroxide adsorption, modulating active sites, and enhancing catalytic kinetics. The Mo-doped Ni₃S₂/FeNi₂S₄ electrode delivers an overpotential of 220 mV at 50 mA cm⁻² in 1.0 M KOH (without iR compensation). It exhibits a low Tafel slope of 41.7 mV dec⁻¹ with excellent long-term stability over 50 h in half-cell OER testing. When implemented as the anode in a single-cell AEMWE with a Pt/CC cathode, it achieves cell voltages of 1.66, 1.85, 1.98, and 2.18 V at 1, 2, 3, and 5 A cm⁻², respectively, at 60 °C, corresponding to theoretical energy consumptions of 45.2–58.0 kWh kg⁻¹ H₂ and voltage efficiencies of 86.5–67.4% (assuming 100% H₂ selectivity). Over 200 hours of continuous operation at 0.5 A, the cell voltage increased gradually from ≈1.65 V to ≈1.80 V, with the electrode retaining ∼91.7% of its initial performance, underscoring its robust structural and interfacial stability under prolonged alkaline conditions. These results highlight the potential of Mo-doped Ni₃S₂/FeNi₂S₄ as a low-cost, high-performance anode for practical AEM water electrolysis, with further device-level optimization and direct hydrogen quantification planned for future studies.