The catalytic activity and stability of an iron-nickel based oxygen-deficient perovskite for the oxygen evolution reaction (OER) are drastically improved with the ppm additive of Fe ions to the alkaline electrolyte. The enhancement is attributed to a 1–2 nm restructured Ni_0.5Fe_0.5O_x(OH)_2-x (oxy)hydroxide layer, as demonstrated with scanning transmission electron microscopy. La_0.6Ca_0.4Fe_0.7Ni_0.3O_2.9 shows almost a four-fold increase in OER activity after Fe addition relative to the as-prepared pristine electrolyte, which demonstrates the low Tafel slope of 44 ± 2.4 mV dec⁻¹ and the superior intrinsic activity of 706 ± 71 A g⁻¹_oxide at 1.61 V vs. RHE.

Preserving transition metal gradients in Ni-rich layered oxides was achieved without using high-valence oxide additives at relatively low processing temperature (650 °C) using a developed diffusion model for transition metals in spherical particles.