3D Nanorod-Shaped Binder-Free Ni1−xFexCo2O4 Anodes Demonstrate High Performance and Stable Operation Under Accelerated Stress Tests in Anion Exchange Membrane Water Electrolysis

Abstract

Platinum-group-metal-free catalysts represent a necessary economic choice for industrial-scale anion exchange membrane (AEM) electrolyzers. A three-dimensional binder-free spinel Ni_1−xFe_xCo₂O₄ (x = 0.1–0.4) electrocatalyst is synthesized directly on nickel felt via a urea-mediated sono-hydrothermal method. The nanorod-shaped morphology is chosen to reduce mass-transfer limitations while maintaining catalyst activity. NiFeCo-2 (20% Fe) offers the optimal balance of iron content, lattice modification, homogeneous nanorod coverage, and surface area, showing the best oxygen evolution reaction (OER) activity, giving 282 mV overpotential at 10 mA cm⁻² and 53 mV dec⁻¹ Tafel slope. As the anode in an anion exchange membrane water electrolyzer (AEMWE), NiFeCo-2 reaches 1.748 V at 1 A cm⁻², 1.92 V at 2 A cm⁻², and 2.09 V at 4 A cm⁻² in wet cathode mode, and sustains stable operation through two 72-h accelerated stress test sequences under both wet and dry cathode feeding. Operation starting in dry cathode mode shows better performance retention than in wet mode. Post-test electron microscopy and textural analysis confirm that the nanorod catalyst layer remains largely preserved, indicating that the observed voltage increase is consistent with resistance growth rather than catalyst loss. These results highlight binder-free Ni_1−xFe_xCo₂O₄ as a promising, affordable anode for AEM water electrolysis.