Efficient Anion Exchange Membrane Water Electrolysis on Amorphous Spray-Pyrolyzed NiFe2O4

Abstract

In the present study, the influence of crystallinity and synthesis method of a NiFe₂O₄ catalyst for anion exchange membrane water electrolysis (AEMWE) is systematically investigated. Catalysts are prepared using an aerosol-assisted spray-pyrolysis approach, both with and without post-calcination treatment, and a co-precipitation method. The spray-pyrolysis approach produces amorphous particles, whereas the co-precipitation and post-calcination result in partial crystallization of the particles. Notably, the post-calcinated catalyst demonstrated the highest degree of crystallinity, corresponding to reduced catalytic activity and stability. Employing the amorphous NiFe₂O₄ catalyst provides the highest activity with an iR_HF-free cell voltage of 1.565 V at 1 A cm⁻². By utilizing a Nafion instead of a PiperION ionomer the iR_HF-free cell voltage is further lowered by 37 mV. Moreover, in this configuration the cell performance remained stable, with a degradation rate of only 91 μV h⁻¹, over 200 h at 3 A cm⁻² and 80 °C with a cell voltage of just 1.8 V. These findings highlight the critical role of amorphous anode catalysts in achieving both high performance and enduring stability in AEMWE applications, suggesting pathways for future catalyst optimization.