Determining the Electrochemically Active Area of IrOx Powder Catalysts in an Operating Proton Exchange Membrane Electrolyzer

Iridium oxide is one of the most common anode catalysts in commercial PEM electrolyzers because of its strong mix of high activity and stability under oxygen evolution reaction (OER) conditions. Unfortunately, benchmarking iridium oxide OER catalysts has proven difficult since it does not have the ability to underpotential adsorb protons like platinum and other transition metal eletrocatalysts, making it difficult to estimate the electrochemically active surface area (ECSA), as well as OER specific and mass activity. In this work, we determined an ECSA-CV pseudocapacitive charge correlation for IrO_x (cm²/C) that was used to determine the in-situ electrochemically active surface area of iridium oxide in an operating PEM electrolyzer. The ECSA-charge correlation will be reported along with the in-situ catalyst utilization and both the specific and mass activity of IrO_x for the OER.