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

Ternary mixed oxides of Fe, Ni and Mo with molecular formulas FexNi1−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.

► Ternary mixed oxides were prepared by partial replacement of Ni by Fe in the NiMoO4. ► Molecular formulas of the oxides were FexNi1−xMoO4(x = 0.25, 0.50, & 0.75). ► Prepared oxides were characterized as electrocatalysts for OER in alkaline solutions. ► The apparent electrocatalytic activity increased with Fe. ► The greatest electrocatalytic effect was observed with Fe = 0.75.