Enhancing Reproducibility and Uniformity of RDEs: Spray-Coating vs Drop-Casting for IrO_<b>2</b> OER Catalyst

The thin-film rotating disk electrode (TF-RDE) technique is widely used for catalyst screening in oxygen evolution reaction (OER) studies due to its ability to separate mass transport from redox kinetics and its low catalyst requirement. However, the manual drop-casting method frequently yields unsatisfactory reproducibility, primarily due to the “coffee-ring” effect, caused by nonuniform catalyst distribution, leading to inconsistent measurements. This study proposes an automated spray-coating method for depositing commercial iridium oxide (IrO2) nanoparticles on RDEs as a reliable alternative. Spray-coating ensures uniform catalyst layers, significantly improving the reproducibility in electrochemical measurements. A comparison of the morphology and the electrochemical properties of the catalyst layers prepared by both methods identifies the sources of the performance variations. Requiring minimal catalyst loading (0.10 mg cm–2), spray-coating establishes a standardized approach for OER catalyst evaluation, offering improved consistency and accuracy in electrochemical characterization.