Iron Integration in Nickel Hydroxide Matrix vs Surface for Oxygen-Evolution Reaction: Where the Nernst Equation Does Not Work.

This study focuses on the oxygen-evolution reaction (OER) activity comparison between two forms of NiFe (hydr)oxides: compound 1 , where Fe ions are applied on the surface of nickel (hydr)oxide, and compound 2 , with Fe ions incorporated into the structural matrix of nickel (hydr)oxide. The observed exponential link between Coulombic energy and the total charge of the system points to a direct proportionality between the potential and the concentration of oxidized nickel ions (e.g., V ∝ [oxidized Ni]), diverging from the logarithmic relationship outlined in the Nernst equation or its modifications, which is not evident in this case. Initial visible spectroscopy indicates a notable trend toward oxidation. As, during the oxidation, more Ni is oxidized, a repulsion effect develops, diminishing the likelihood of further oxidation, and a distinct linear correlation emerges between the quantity of oxidized Ni(II) and the applied potentials.