Advances in materials and surface engineering for fuel cell bipolar plates: Materials, coatings

Energy sustainability and environmental concerns have driven the proton exchange membrane fuel cell (PEMFC) technology to become one of the most promising clean energy systems, because of its high efficiency, zero emissions and flexibility in applications to transportation or stationary power generation fields. Bipolar plates (BPs) are key components of PEM fuel cells, which provide efficient electron conduction, reactant distribution, water and heat management, and mechanical support. Learned from commercialization lessons of Stack, aluminum alloys are materials of interest as BPs due to low density, strong electrical/thermal conductivities and economic considerations; however, they suffer from corrosion and high interfacial contact resistance during FC operation. This article systematically compiles the progress in alloy selections, advanced fabrication processes, ideal flow field patterns, as well as new surface engineering approaches (e.g., TiN, CrN, diamond-like carbon and conductive polymer composites (CPCs)) which can greatly enhance the BPs' corrosion resistance, electrical properties and service life. The paper also presents established international testing procedures and U.S. DOE targets for key performance parameters. This focus crosses the boundaries of scalable, then commercially viable, coating processes as well as challenges with uniform electrochemical testing and long-term BP stability. Future research directions suggested are accelerated ageing tests, computational modelling for design optimization, and finding sustainable, scalable surface treatments. Through combining material breakthroughs, fabrication processes, performance characteristics and prospective strategies, this article offers an essential guideline to realize durable, lightweight and affordable BPs for promoting PEMFC application in the worldwide trend of sustainable hydrogen energy.