Flow-Field Designs for PEM Water Electrolysis Cells: Performance and Contact Behavior

Introduction This study examines the influences of flow field designs on Proton Exchange Membrane (PEM) water electrolysis cells. The flow field structure has an impact on fluid and heat distribution which in turn influences the performance locally [1]. In addition, different designs affect the mechanical compression through the layers. This can lead to unfavourable contacting between the layers, which also affect the cell performance. Methods Ten different flow field designs are tested in a 4 cm 2 single cell setup. The designs include a variation of parallel channel and rib widths and distances (Fig 1.a), a serpentine channel arrangement (Fig 1.b), planar geometries without connecting channels (Fig 1.c) and block geometries (Fig 1.d). Polarisation curves and high frequency resistance (HFR) are measured and Tafel analysis are done to evaluate the performance. Residual overpotentials including mass transport are extracted. Additionally, pressure measuring films are used to qualitatively measure the mechanical pressure distribution in the membrane-electrode assembly (MEA). Results The HFR of the different designs differs by up to 32 %. This is the main driver in the polarisation curve differences shown in Fig. 2. However, it appears that the flow field structure (channel width, channel position) and contact area between end-plate and PTL is strongly affecting the interface of the porous transport layer (PTL) and the MEA in a multiple manner. A poorly designed flow field leads to electrochemically inactive MEA areas, whereas optimal designs benefit from a homogenous mechanical pressure distribution for optimal contact between PTL and MEA. This also influences the residual overpotential in different ways. References [1] A. C. Olesen, S. H. Frensch and S. K. Kær, Electrochimica Acta, 293, 476–495 (2019). The authors gratefully acknowledge funding by BMWK (German Federal Ministry of Economic Affairs and Climate Action) in the framework of the project TICOB (FKZ 03EI3048B). Figure 1