The proton exchange membrane fuel cell (PEMFC) is a promising device for the transportation sector of a fossil free society, using green hydrogen from water electrolysis as a clean and sustainable option. However, sluggish kinetics as well as durability issues limit the implementation until this day. Therefore, modifications to the platinum catalysts [1] and the carbon supports [2] are made to improve the overall performance and durability of the cathode catalyst system. Herein, we present the investigation of the carbon corrosion behavior of different carbon support materials in PEMFCs using online nondispersive infrared (NDIR).The different carbon supports used for this study are commercial materials such as Vulcan, Ketjenblack EC-300J and Ketjenblack EC-600JD as well as self-synthesized mesoporous carbon nanodendrites (MCND). [3] The MCND support material is a highly porous high surface area carbon, which makes it a suitable candidate for fuel cell applications. Onto the support materials, Pt nanoparticles were deposited using a customized fluidized bed reduction reactor [4], resulting in similar Pt particle size and distribution onto the support material, thus making a comparison between different supports possible. Beginning of life (BOL) measurements in a single cell setup, as shown in Figure 1, show promising performance of the platinum catalyst supported on MCND (Pt/C_MCND) compared to the platinum catalysts on commercial supports. Furthermore, we will present the investigated carbon corrosion behavior of the different support materials conducted by accelerated stress tests (AST) based on the DOE support degradation protocol. The online quantification of the evolved CO and CO₂ from the cathode catalyst layer is measured using our online NDIR giving insight in the carbon corrosion resistivity of the different support materials. Together with the performance measurements, we develop a better understanding of the impact of the carbon support material on the performance and durability of the cathode catalyst layer. Literature: [1] Strasser, P; Kühl, S. Nano Energy 2016, 29, 166. [2] Ott, S. et. al., Nat. Mater. 2020, 19 (1), 77-85. [3] Numao, S. et al., Carbon 2009, 47, 306-312. [4] Hornberger, E. et. Al. J. Electrochem. Soc. 2020, 167, 114509. Figure 1: Air polarization curves of the four different catalysts under the following conditions: 80° C, 100% RH, 150 kPa_abs backpressure, stoich.: 1.5 (H₂) and 2 (air), min. flow: 50 ml/min (H₂) and 800 ml/min (air). Figure 1