Integration of Thin Laser Structured Micro Porous Layers in PEM Water Electrolyzers
Authors: Trinke Patrick , Wienke Alexander , Benecke Mareike , Stein Lukas , Bensmann Boris , Koch Jürgen , Hanke-Rauschenbach Richard 
Published: December 2024

Reduction of the Iridium loading of Proton Exchange Membrane (PEM) water electrolyzers is an important topic to reduce the capital costs and increase the sustainability. At high Iridium loadings (>1 mgIr cm-²) the interface between porous transport layer (PTL) and catalyst layer (CL) has influences on the electrochemical performance. However, this is significantly more important at low and especially ultra-low loadings: <1 mgIr cm-², < 0.1 mgIr cm-², respectively.
At low catalyst loadings the electrical conductivity of such catalyst layers is significantly reduced, because of local inhomogeneity’s, e.g. not connected catalyst particles/agglomerates. There is a large mismatch between pore/particle sizes of both layers that lead to a bad electrical contact: commercial titanium PTLs have pore sizes of 30 µm [1], on the other hand catalyst particles are in the size of few nm [2]. Furthermore, the titanium tends to oxidize on the anode side, which leads to further increases of the resistances between PTL and CL. Because of these aspects protective, good conducting coatings on the PTL are used (often noble metals, e.g. Platinum, Iridium). Another favorable improvement is the integration of micro porous layers (MPL) to reduce the interface resistances [3]. However, it is not easy to manufacture such MPLs.
In our approach we produce ultra thin MPLs with thicknesses of 10 µm. As base material we use titanium foils (grade 1) that are processed with laser precision machining to produce deterministically structured pores in the size of ≤ 5µm. These laser structured MPLs are integrated between PTL and CL.
The experimental results show a significant improvement when using MPLs (Fig. 1a). The polarization behavior is clearly better because of the reduced resistances (Fig. 1b), which were measured by electrochemical impedance spectroscopy.
This contribution deals with the improvement of the interface between PTL and CL by integrating thin MPLs to enable further reductions of Iridium loadings. By means of laser precision machining we can produce thin MPLs with deterministically structured pores. We will show the effect of different structural properties of the MPLs, such as pore sizes or pore distribution, on the electrochemical performance in combination with low loading CCMs.

References

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[2] H. Yu, N. Danilovic, Y. Wang, W. Willis, A. Poozhikunnath, L. Bonville, C. Capuano, K. Ayers and R. Maric, Applied Catalysis B: Environmental,
239, 133–146 (2018).
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14(7), 2302786 (2024).

Acknowledgments

The authors gratefully acknowledge funding by the German Federal Ministry of Education and Research (BMBF) in the framework of project NEO-PEM (FZK: 03SF0762A)

Figure 1