Towards cost-effective and durable bipolar plates for proton exchange membrane electrolyzers: A review

As an attractive and flexible energy storage technology for converting surplus renewable electricity into hydrogen energy, proton exchange membrane (PEM) water electrolysis will become a critical route of green hydrogen production in the future decades. Currently, the application of PEM electrolysis is retarded largely because of the high cost of stacks. As one key component, the bipolar plates (BPs), typically made of costly titanium substrate and noble-metal protective coatings against harsh electrochemical corrosion, account for more than one-third of the PEM electrolysis stack cost. The manufacturing cost of BPs can be significantly reduced by using cost-effective substrates and coating materials, as well as optimized coating structure design and high efficiency manufacturing. In this paper, the technical status and progress in materials and coatings for PEMWE BPs are reviewed, with special focus in the cost reduction and durability improvement strategies. Firstly, the metallic substrates of BPs (titanium, stainless steel, aluminum, copper, etc.) and degradation mechanisms under PEM electrolysis operation are summarized. Subsequently, noble metal, transitional metal, nitrides, and oxides coating materials, as well as singe-layer, multi-layer and microdot structural designs of the protective coatings are reviewed. Lastly, the state-of-art manufacturing technologies for achieving cost-effective BPs of high corrosion resistance and interfacial contact conducting properties are summarized and compared.