Conformal Corrosion-Resistant Coatings for Fuel Cell Bipolar Plates by Atomic Layer Deposition (ALD)

Polymer electrolyte membrane fuel cells (PEMFCs) are promising for heavy duty vehicles, however increasing the operating cell voltage to improve energy conversion and fuel efficiency can lead to electrochemical corrosion of metallic bipolar plates (BPP). Several corrosion mechanisms can occur simultaneously releasing metal ions that poison the membrane impacting the overall performance of the PEMFC. Preventing the degradation of metallic bipolar plates will enable cheaper, durable BPPs with significant volumetric and gravimetric power density advantages over alternative (graphite) BPP materials necessary for adoption in heavy duty vehicles. RMD Inc. will address this challenge with the Atomic Layer Deposition (ALD) to grow a conductive, protective coating on metallic BPPS, preventing corrosion and thus enhancing the lifetime of BPPs. ALD is the ideal choice for applying protective coatings on BPPs, as ALD is an inherently scalable surface-reaction-based thin film growth technique that can provide conformal, pinhole-free coatings with excellent step coverage on the complex flow fields of BPPs. Furthermore, ALD coatings can be re-applied on refurbished BPPs after appropriate surface cleaning. RMD Inc. will deposit candidate transition metal nitrides that are conducting with promising corrosion resistance on stainless steel coupons (provided by Cummins Inc.) and evaluate the coatings conductivity and corrosion resistance der galvanostatic operation in a 3-electrode cell that simulates fuel cell conditions. Based on these tests, a “hero” ALD candidate will be downselected and deposited on BPPs that are provided by Cummins Inc. The ALD-coated BPPs will be installed in a test fuel cell and benchmarked by Cummins Inc. against an equivalent cell with uncoated BPPs. The resulting data will demonstrate feasibility of the proposed approach. The proposed development of the conductive, protective coating will improve the long-term stability of metallic BPPs, enabling the utilization of PEMFCs in heavy duty vehicle applications increasing the hydrogen economy linked to the use of clean, renewable energy. Such coatings could also find application for SOEC stack technologies and other fuel cell stack technologies.