Green hydrogen production can only be realized via water electrolysis using renewable energy sources. Proton exchange membrane water electrolyzers have been demonstrated as the technology of choice for mass production of green hydrogen due to their scalability and potential high efficiency. However, the technology is still relatively expensive due to the catalyst materials cost and operational limitations due to mass transfer and activation polarizations. During the oxygen evolution reaction, oxygen bubbles stick to the electrode surface and this causes a low reaction rate and high mass transfer losses. In this study, the commonly used electrocatalyst for oxygen evolution reactions; IrO2, is modified by intro-ducing magnetic Fe3O4 to achieve greater bubble separation at the anode during operation. The prepared composite catalysts were characterized using Scanning Electron Microscope, Energy Dispersive X-Ray Analysis, X-Ray Powder Diffraction, X-ray photoelectron spec-troscopy and Brunauer-Emmett-Teller characterization methods. The modified composite electrocatalyst samples are magnetized to investigate the magnetic field effect on oxygen evolution reaction performance in proton exchange membrane water electrolyzers. 90% IrO2-10% Fe3O4 and 80% IrO2-20% Fe3O4 samples are tested via linear sweep voltammetry both ex-situ and in-situ in a proton exchange membrane water electrolyzer single cell. According to the linear sweep voltammetry tests, the magnetization of the 80% IrO2-20% Fe3O4 sample resulted in 15% increase in the maximum current density. Moreover, the single cell electrolyzer test showed a four-fold increase in current density by employing the magnetized 80% IrO2-20% Fe3O4 catalyst. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.