Oxygen-evolution reaction by nickel/nickel oxide interface in the presence of ferrate(VI)

In this study, we investigate the effect of K₂FeO₄, as a new and soluble Fe salt at alkaline conditions, on oxygen-evolution reaction (OER) of Ni oxide. Both oxidation and reduction peaks for Ni in the presence and absence of Fe are linearly changed by (scan rate)^1/2. Immediately after the interaction of [FeO₄]^2- with the surface of the electrode, a significant increase in OER is observed. This could be indicative of the fact that either the [FeO₄]^2- on the surface of Ni oxide is directly involved in OER, or, it is important to activate Ni oxide toward OER. Due to the change in the Ni(II)/(III) peak, it is hypothesized that Fe impurity in KOH or electrochemical cell has different effects at the potential range. At low potential, [FeO₄]^2- is reduced on the surface of the electrode, and thus, is significantly adsorbed on the electrode. Finally, oxygen-evolution measurements of K₂FeO₄ and Ni₂O₃ are investigated under chemical conditions. K₂FeO₄ is not stable in the presence of Ni(II) oxide, and OER is observed in a KOH solution (pH ≈ 13).