Abstract
Water management in polymer electrolyte fuel cells (PEFC), particularly the accumulation of liquid product water in the gas diffusion layer (GDL) on the cathode side, which mitigates the oxygen transport towards the catalytic surface, must be optimized for ideal performance [1]. The potential of 3D-printing has recently gained interest in the field of electrochemical flow cells to investigate and improve mass transport in porous transport layers of various applications, including PEFC [2,3,4].In this study we explore different 3D-printed structures that are used as cathode GDLs for PEFC. The objective is to guide the liquid product water through determined pathways by adjusting the throat size to form preferential percolation routes according to Young-Laplace law [5]. The GDLs are obtained from a 3D-printed polymer precursor that is subsequently carbonized in a tube furnace (Tc = 1200°C in N2 atmosphere, result shown in Figure 1a) and treated with a hydrophobic surface coating. The structures are assembled in a cell designed for X-ray diagnostics together with a commercial Freudenberg H2315C2 anode GDL and a Gore Primea CCM (A510.1/M815.15/C510.4) to form the membrane electrode assembly (MEA). The cross-section of one of these cells obtained from X-ray tomography is exemplarily shown for a “through-plane” cathode GDL in Figure 1b. To track the liquid water distribution and saturation in the GDL we perform current jumps from dry state to various current densities and employ operando X-ray radiography with a Lab CT, with a frame rate of 2 Hz. Additionally, the 3D water distribution after reaching steady state is captured by X-ray tomography at the end of each current jump experiment. Furthermore, we measure the electrochemical performance (see Figure 1c) and compare our results to a reference case (Toray, carbon paper GDL). Figure 1 . a) SEM images of the carbonized structure b) Cross section obtained from X-ray tomography of the cell assembly with the through-plane GDL c) Polarization curves and HFR of the through-plane cell as well as a reference cell with a commercial Toray material (two TGP-090 w. 10% PTFE sandwiched together). The cell was operated with H2/Air at T=50°C, p=1bar and 100% relative humidity on both sides References[1] J. Ihonen et. al., Journal of the Electrochemical Society, 2004, 151, pp. A1152-A1161[2] D. Niblett et. al., International Journal of Hydrogen Energy, 2022, 47, pp. 23393-23410[3] M. v. d. Heijden et. al., Advanced Materials Technologies, 2023, 8, 2300611[4] B. Huang et. al., Angewandte Chemie International Edition, 2023, e202304230[5] D. Niblett et. al., Journal of Power Sources, 2020, 471, 228427 Figure 1
Published Version
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