A Comprehensive Review of Stainless-Steel Bipolar Plate Coatings and Their Role in Mitigating Corrosion in Aggressive Proton-Exchange Membrane Fuel Cells Environments

Proton exchange membrane fuel cells (PEMFCs) are garnering growing interest as both portable and stationary power sources in the pursuit of a carbon–neutral society. Bipolar plates (BPs) plays a crucial role in facilitating the supply of reactant gases to each electrode, preventing the intermingling of fuel and air, and dissipating the heat generated during electrochemical reactions in PEMFCs. Recently, the utilization of metal BPs in PEMFCs has become prevalent. However, the operation of PEMFCs in acidic and humid conditions may result in metal corrosion and degradation of the BPs. Over time, metal ions are released from the BPs due to prolonged corrosion. The elution of ions has the potential to pollute both the catalyst and the membrane electrode assembly, thereby diminishing the performance and longevity of the PEMFCs. The mitigation of these issues can be achieved through the application of protective coatings to safeguard the surface. Materials such as metals such as precious metals and alloys, ceramics such as nitrides and oxides, polymers, and composites are applied to metal BPs to improve corrosion resistance. This review focuses on enhancing the corrosion resistance and electrical conductivity of BPs in PEMFCs through a detailed analysis of different coating materials and techniques, as well as proposing future research directions.