The storage of renewable energy using hydrogen “fuel” has been viewed as a viable mechanism by electrolysis of water into oxygen and hydrogen fuels, but is hampered by the slow kinetics of the oxygen evolution reaction (OER). Hence there is a broad effort to improve performance of currently used materials and develop new materials. Iridium oxide (IrO₂) is an effective stable electro-catalyst which can lower the over-potential and keep a remarkable current to improve the efficiency of fuel generation technologies. To further improve its activity with novel nanostructures synthesized by facile and reliable methods, here ultrafine iridium oxide nanocrystals (IrO₂ NCs) were successfully synthesized using a facile one-step molten salt synthesis process at 650 ^oC in air. To tune the size and morphology of these IrO₂ NCs, three molar ratios of IrCl₄, NaCl, and KCl were employed, specifically 1:10:10, 1:30:30, and 1:60:60. The structural and morphological characterizations of these IrO₂ NRs were carried out by powder X-ray diffraction, Raman spectroscopy, Infrared spectroscopy, X-ray photoelectron spectroscopy, and electron microscopic techniques. The electrocatalytic performance of these IrO₂ NCs for OER in acidic media was compared with that of commercial IrO₂ nanoparticles (NPs) and the annealed derivative in terms of specific capacitance, total charge, most accessible charge, electrochemically active surface area, and roughness factor. The as-synthesized IrO₂ NCs show enhanced electrocatalytic OER activity in 0.5 M H₂SO₄ media compared to the commercial IrO₂ NPs before and after annealing. Among all five IrO₂ samples, IrO₂ NCs synthesized with the ratios of IrCl₄:NaCl:KCl = 1:60:60 and 1:30:30 demonstrated better OER activity than commercial IrO₂ NPs while the annealed commercial IrO₂ NPs showed the worst performance. Moreover, compared to commercial IrO₂ NPs and previous reports, the IrO₂ nanorods show enhanced electrocatalytic activity to oxygen and hydrogen evolution reactions by passing either N₂ or O₂ gas in a 0.5 M KOH electrolyte before electrochemical measurements, including cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Our results are comparable with, and in most cases, higher than reported data in the literature. Therefore, the current study reports a novel, reliable and scalable synthetic process from iridium tetrachloride salt for IrO₂ nanostructures, but also a type of highly electrocatalytic efficient IrO₂ nanostructures. It is expected that these IrO₂ NCs can serve as a benchmark in the development of active OER and HER (photo)electrocatalysts for various applications.