Enhanced oxygen evolution reaction over glassy carbon electrode modified with NiOx and Fe3O4

Magnetite iron oxide (Fe3O4)/nickel oxide (NiOx) modified glassy carbon (GC) electrode shows enhancement of oxygen evolution reaction (OER) compared to GC electrode modified with single NiOx or Fe3O4 nanoparticles. Many techniques such as linear and cyclic sweep voltammetry, electrochemical impedance spectroscopy (EIS) have been employed. Field-emission scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are both used for characterization of the electrocatalysts. Effect of loading amount of both NiOx and Fe3O4 and the order of deposition on the OER was studied. A significant improvement of the electrocatalytic properties of the Fe3O4/NiOx binary catalyst modified GC is obtained when NiOx is electrodeposited on GC/Fe3O4 (i.e. GC/Fe3O4/NiOx) compared to GC/NiOx/Fe3O4 (where NiOx is deposited first on the GC then Fe3O4). The use of GC/Fe3O4/NiOx (where Fe3O4 is deposited first on the GC then NiOx) for OER in alkaline solution support higher currents and consequently negative shifts of the onset potential of OER compared to that of GC/NiOx or GC/Fe3O4. The obtained electrochemical impedance parameters confirmed the above conclusions. Tafel parameters confirm the superior activity of GC/Fe3O4/NiOx and give insight into the mechanism of the OER on the above electrodes.