The development of highly stable and active electrocatalysts for the oxygen evolution reaction (OER) has attracted significant research interest. IrO₂ is known to show good stability during the OER however it is not known to be the most active. Thus, significant research has been dedicated to enhance the activity of IrO₂ toward the OER. In this study, IrO₂ catalysts were synthesized using a modified Adams fusion method. The Adams fusion method is simple and is shown to directly produce nano-sized metal oxides. The effect of the Ir precursor salt to the NaNO₃ ratio and the fusion temperature on the OER activity of the synthesized IrO₂ electrocatalysts, was investigated. The OER activity and durability of the IrO₂ electrocatalysts were evaluated ex-situ via cyclic voltammetry (CV), chronopotentiometry (CP), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). Physical properties of the IrO₂ electrocatalysts were evaluated via X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), and energy dispersive spectroscopy (EDS). The results show that the addition of excess NaNO₃ during the modified Adams fusion reaction is not a requirement and that higher synthesis temperatures results in IrO₂ electrocatalysts with larger particle sizes and reduced electrocatalytic activity.