Electrochemical Study of the Energetics of the Oxygen Evolution Reaction at Nickel Iron (Oxy)Hydroxide Catalysts

Iron-doped nickel (oxy)hydroxide catalysts (FexNi1-xOOH) exhibit high electrocatalytic behavior for the oxygen evolution reaction in base. Recent findings suggest that the incorporation of Fe3+ into a NiOOH lattice leads to nearly optimal adsorption energies for OER intermediates on active Fe sites. Utilizing electrochemical impedance spectroscopy and activation energy measurements, we find that pure NiOOH and FeOOH catalysts exhibit exceedingly high Faradaic resistances and activation energies 40-50 kJ/mol(-1) higher than those of the most active FexNi1-xOOH catalysts. Furthermore, the most active FexNi1-xOOH catalysts in this study exhibit activation energies that approach those previously reported for IrO2 OER catalysts.