The effect of Fe as constituent in Ni-base alloys on the oxygen evolution reaction in alkaline solutions at high current densities.

Abstract Nanocrystalline Nickel-based alloys were investigated as catalysts for the oxygen evolution reaction (OER) at industrial operation conditions for alkaline water electrolysis. Different alloys were prepared by rapid solidification and subsequent high-energy milling. Regarding OER activity, the best efficiency was obtained for a nanocrystalline Ni Fe alloy in 29.9 wt.-% KOH at 298 K. However, at elevated temperature (333 K), comparable activities were determined in short-term experiments for nanocrystalline Ni Fe and Ni alloys as well as for polycrystalline Ni. This initially incomprehensible outcome can be explained by the incorporation of Fe, which is present as impurity in the reagent grade KOH solution, into the NiOOH anode surface layer. However, after a long-term operation, the nanocrystalline Ni Fe alloy shows a significantly better activity, in particular, at altering current density of up to 1 A cm−2. As a result, the nanocrystalline Ni Fe alloy exhibits a very high efficiency and excellent long-term activity (375 mV overpotential at 0.3 A cm−2) after 95 h of operation at different loads. Highlights • Nanocrystalline Ni based alloys were investigated towards OER activity. • Both Fe in the alloy bulk and Fe impurities in the electrolyte affect the OER activity significantly. • Ni Fe alloys are excellent long-term stable catalysts at high current densities up to 1 A cm−2. • Fe-free Ni alloys show low OER activity with a high Tafel slope (b > 350 mV). [ABSTRACT FROM AUTHOR]