New ternary mixed oxides of Fe, Ni and Mo for enhanced oxygen evolution

Ternary mixed oxides of Fe, Ni and Mo with molecular formulas Fe_xNi_1−xMoO₄ (x = 0.25, 0.50 and 0.75) have been prepared by a co-precipitation method and investigated for their structural and electrocatalytic properties by XRD, AFM, electrochemical impedance spectroscopy and anodic Tafel polarization. Results indicate that the apparent oxygen evolution activity of the base (NiMoO₄) electrode significantly increases with introduction of Fe from 0.25 to 0.75 mol. The Tafel slope for the oxygen evolution reaction at low overpotentials is found to be only ∼35 mV on Fe-substituted oxides, while it was ∼75 mV on the base oxide. The reaction follows the first order kinetics with respect to OH⁻ concentration, regardless of Fe content in the oxide.