Electrochemically Activated Ni-Fe Oxyhydroxide for Mimic Saline Water Oxidation

Utilizing renewable energy to produce green hydrogen from saline water electrolysis is becoming increasingly important yet is largely challenged by the sluggish oxygen evolution reaction kinetics, the competitive anodic chlorine evolution reaction, and the resultant electrode corrosion. Here, we report an electrochemically activated Ni-Fe oxyhydroxide catalyst that delivers an early onset potential of 1.51 V at 100 mA cm–2 within mimic saline water of 0.5 M NaCl + 1 M NaOH. During the electrochemical activation, ex situ X-ray radiation and in situ Raman characterizations reveal the structural reconstruction of amorphous Ni (oxy)hydroxide generation and electronic structure modulation from Fe intercalation. Headspace gas chromatography and iodine titration results confirm the ∼100% Faradaic efficiency toward O2 evolution on activated NiFeOxHy, whereas the long-term stability is assessed by an anion exchange membrane electrolyzer, demonstrating only 350 mV voltage decay during the 100 h continuous electrolysis at 500 mA cm–2.