Performance Evaluation and Durability Analysis of NiFeCoOx Catalysts for Alkaline Water Electrolysis in Anion Exchange Membrane Electrolyzers

Abstract

This study examines the catalytic activity of NiFeCoOx catalysts for anion exchange membrane (AEM) water electrolysis. The catalysts were synthesized with a Ni to Co ratio of 2:1 and Fe content ranges from 2.5 to 12.5 wt%. The catalysts were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The catalytic activity of the NiFeCoOx catalysts was evaluated through linear sweep voltammetry (LSV) and chronoamperometry (CA) experiments for the oxygen evolution reaction (OER). The catalyst with 5% Fe content exhibited the highest catalytic activity, achieving an overpotential of 228 mV at a current density of 10 mA cm−2. Long-term catalyst testing for the OER at 50 mA cm−2 showed stable electrolysis operation for 100 h. The catalyst was further analyzed in an AEM water electrolyzer in a single-cell test, and the NiFeCoOx catalyst with 5% Fe at the anode demonstrated the highest current densities of 1516 mA cm−2 and 1620 mA cm−2 at 55 °C and 70 °C at 2.1 V. The maximum current density of 1880 mA cm−2 was achieved at 2.2 V and 70 °C. The Nyquist plot analysis of electrolysis at 55 °C showed that the NiFeCoOx catalyst with 5% Fe had lower activation resistance compared with the other Fe loadings, indicating enhanced performance. The durability test was performed for 8 h, showing stable AEM water electrolysis with minimum degradation. An overall cell efficiency of 70.5% was achieved for the operation carried out at a higher current density of 0.8 A cm−2.