(Invited) Innovative Low Cost Bipolar Plates and Current Collectors for Proton Exchange Membrane Electrolyzers
Authors: Gago Aldo Saul , Lettenmeier Philipp , Friedrich K. Andreas 
Published: February 2020

Hydrogen produced by proton exchange membrane (PEM) electrolysis technology is a promising solution for energy storage, integration of renewables, and power grid stabilization for a cross-sectorial green energy chain. The most expensive components of the PEM electrolyzer stack are the bipolar plates (BPP) and current collectors (CC), also called gas diffusion layers (GDL). These components account together for 50 to 70 % of the stack cost depending on the design [1,2]. Their high cost is due to the fact that the employed materials need to withstand corrosion at high anodic potentials in acidic environment. Currently, only Ti is the material of choice for the anode side. However, a semi-conductive oxide layer grows on its surface over time. In this context, a lucrative solution is to replace the Ti BPPs by coated stainless steel. Vacuum plasma spraying (VPS) technology can be used to produce highly dense Ti coatings to protect stainless steel BPPs from the oxidative conditions in the anode side. Surface modifications with Au [3] or Pt [4,5] improve the conductivity of the Ti coating, but we have also developed promising non-noble conductivity enhancement elements improving the long-term stability of the electrolyzer [6]. Furthermore, a macro-porous layer (MPL) on Ti CCs can be realized by VPS as well, improving largely the performance of the electrolyzer at high current densities [7]. Lastly, an entire pore-graded CC with optimized tortuosity and capillary pressure is developed by VPS (Figure 1). Tests in PEM electrolyzer demonstrate high performance and a significant decrease in mass transport limitations. This contribution will discuss the state-of-art of BPPs and CCs developments as well as their potential for future improvements.
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Figure 1