Calibration for the quantification of anode and cathode catalyst loadings for polymer electrolyte membrane electrolyzers via X-ray fluorescence spectroscopy

Precious metals, most commonly Ir and Pt, used as catalysts in polymer electrolyte membrane electrolysis are a significant cost factor, making the determination of their loading an important question. X-ray fluorescence is an established analysis method to determine metal loadings at both laboratory and industrial scale. The application towards catalyst coatings in polymer electrolyte membrane electrolyzers is limited by variability in layer composition, absorption within layers, and high peak overlap, which lower accuracy. In addition, reference loadings are often determined by weighing, which is prone to errors. In this work, calibration strategies are discussed which can alleviate some of these limitations. Namely, the strategy in calibration sample creation can enable different reference methods and higher variability of measurements. In addition, non-linear calibration curves and tuning of calibration ranges can further improve calibration success. Overall, the average quantification error for Ir and Pt can be lowered from 31% to 7-8%.