Simple Aqueous Preparation of High Activity and Stability NiFe Hydrous Oxide Catalysts for Water Oxidation

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  • A series of Ni1–xFex hydrous oxide nanoparticles (HO-nps, x = 0–0.5, 1) were prepared by stirring 0.1 M KOH solutions of NiCl2 and FeCl2 under air at room temperature. The resulting HO-nps can be used directly, or washed and isolated without loss of activity. The Ni1–xFex HO-nps are outstandingly active and stable toward the water oxidation reaction (WOR) in base. The Ni0.75Fe0.25 HO-np was the most active mass-normalized WOR catalyst in the series, with onset overpotential = 190 mV, Tafel slope = 24 mV dec–1, overpotential at 10 mA cm–2 = 234 mV, and loadings Ni + Fe = 0.135 mg cm–2. The catalysts were robust under long-term galvanostatic and duty-cycle testing. The Ni0.75Fe0.25 HO-np catalyst has a layered double hydroxide structure, and it appears that Fe enhances the activity of Ni toward the WOR by decreasing its electron density.

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    Attribution-NonCommercial 4.0 International