A new simultaneous membrane thickness and catalyst loading measurement for fuel cell proton-exchange assemblies by IR transmission

We present a study of mid-infrared (mid-IR) transmission through typical proton-exchange fuel cell and water electrolyzer catalyst-coated membrane materials, and the determination of membrane layer thickness, and catalyst layer loading, from the power of the transmitted beam. Measured membrane thicknesses lay in the range of 25–125 μm, and catalyst areal loadings range from 0.05 to 0.35 mg/cm2. We show that the transmission spectrum correlated to membrane thickness and catalyst loading values separately, and also used a mathematical model to calculate both quantities simultaneously, from a single measurement of transmission. Measurements were carried out using a Fourier-transform infrared (FTIR) spectrometer, in specular transmission mode, in the wavelength range of 3–13 μm (3333–770 cm−1). We discuss the potential application of this method to the development of roll-to-roll manufacturing full-area-scanning quality inspection of catalyst-coated membrane (CCM) materials. •Fuel cell membrane thickness and catalyst loading measured by MIR transmission.•Single MIR measurement measures both thickness and loading simultaneously.•Measurements are done using a widely-used type of FTIR spectrometer.•A simple numerical model relates transmission to thickness and loading.•Error 22% or less for membranes, 12% or less for catalyst-coated membranes.