Unified anodes with different nickel–iron-based phases for durable AEM electrolyzers achieving high performance of 8000 mA cm−2 at 2.05 V

Abstract

Investigating the different nickel–iron (NiFe) phases in anion-exchange membrane water electrolyzer (AEMWE) anodes is important for enhancing the performance and durability of AEMWEs. In this study, a NiFe-based unified electrode is prepared to investigate the optimal phases for a highly efficient and durable AEMWE anode. Three different unified electrodes are prepared: electrodes with heat treatment (HT) in air and argon (Ar) atmospheres, and electrodes without HT. NiFe oxyhydroxide (NiFeOOH) exhibits the highest oxygen evolution reaction (OER) activity and stability. In the single-cell test, the optimized NiFeOOH electrode achieved an outstanding performance of 4880 mA cm⁻² at 1.9 V and 8000 mA cm⁻² at 2.05 V. This performance is superior to values reported in the literature. The NiFeOOH unified anode remains durable under AEMWE operation, maintaining stable performance at 1000 mA cm⁻² without significant loss for 350 h. A 5-layer AEMWE stack employing the same electrode exhibited excellent durability for 200 h with a faradaic efficiency of 83.8%. Thus, a unified anode with NiFeOOH is considered a promising anode design for AEMWEs.