Review on bipolar plates for low‐temperature polymer electrolyte membrane water electrolyzer

Electrolysis coupled with renewable energy resources is the most promising method for green hydrogen production. Polymer electrolyte membrane water electrolyzer (PEMWE) has attracted attention due to its ability to produce high-purity, compressed hydrogen at relatively mild operating temperatures (70°C-90°C). The highest cost contributor of the PEMWE stack are the bipolar plates (BPPs). Owing to the severe operating conditions (acidity from the membrane and high localized oxygen concentration) of the PEMWE stack, appropriate material and fabrication are crucial to ensure high performance and durability. The role of BPPs in mass transport and electrical charge transfer must be further understood and correlated to its specific application in PEMWE. At the most basic level, BPPs must have low interfacial contact resistance and high corrosion resistance to withstand the conditions within the stack. The most common base materials for BPP construction include austenitic stainless steel (SS316 and SS403) and Ti due to their flexural strength and ease of mass production. A coating layer is also necessary to protect the substrate from corrosion, and the most popular materials include TiN and other noble metals with nonpassivated oxides and reliable electrical conductivity. The compromise between material robustness and cost is currently a delicate balance toachieve.