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This work presents a study on the influence of the addition of cobalt into state‐of‐the‐art nickel–iron (NiFe) mixed oxides/hydroxides/(oxy)hydroxides on their structural and morphological properties, and oxygen evolution reaction (OER) catalytic activity. A one‐step electrodeposition process is performed without any additives to fabricate NiFe and x cobalt‐doped nickel/iron (xCoNiFe) layer‐double‐hydroxide catalysts directly on nickel foam. The addition of cobalt nitrate in the synthesis solution significantly affects the final form of the catalyst: the addition of 2 mm cobalt nitrate into the aqueous solution of 4 mm nickel and iron nitrate stabilizes the electrochemical synthesis of the catalyst, which leads to the formation of a homogenously spread 3D interconnected structure with a high electroactive surface area (0.07 cm2, 1.1 m2 cm−2: including nickel foam substrate); it induces the formation of Ni3+ desirable for the formation of the catalytically active (oxy)hydroxides, which is not observed for the state‐of‐the‐art NiFe. The significant role of the addition of cobalt translates into improved preliminary OER catalytic stability and activity of the catalyst with an onset potential of 1.40 V, overpotential of 224 mV determined at 10 mA cm−2, and only 0.7% loss in stability after 22 h working in alkaline conditions compared with the initial parameters.

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