Bipolar plates gold coated

Bipolar plates are currently made from milled graphite or gold-coated stainless steel. Ongoing research is aiming to replace these materials with polymers or low-cost steel alloys, which will allow the use of low-cost production techniques. Even today, bipolar plates can be produced at 200 /kW, if the production volume... 

Corrosion of the plates not only detracts from their mechanical properties but also gives rise to undesirable corrosion products, namely, heavy-metal ions, which, when depositing on the catalysts, strongly depress their activity. The corrosion processes also give rise to superficial oxide films on the metal parts, and these cause contact resistance of the surfaces. For a lower contact resistance, metallic bipolar plates sometimes have a surface layer of a more stable metal. Thus, in the first polymer electrolyte membrane fuel cell, developed by General Electric for the Gemini spacecraft, the bipolar plates consisted of niobium and tantalum coated with a thin layer of gold. A bipolar plate could also be coated with a layer of carbide or nitride. 

Fig. 14.16 Selection of bipolar plates having identical flow fleld design investigated within the DECODE project, (a) Uncoated metallic bipolar plate (0.1 mm SS 316 L), (b) gold coated metallic bipolar plate (200 nm Au on 0.1 mm SS 316 L), (c) milled graphite composite bipolar plate. Pictures courtesy of Reinz Dichtungs GmbH, DANA Corporation...

Wang, Y. and Northwood, D. O. 2008. An investigation into the effects of a nano-thick gold interlayer on polypyrrole coatings on 316L stainless steel for the bipolar plates of PEM fuel cells. Journal of Power Sources 175 40—48. 

Yun, Y.-H. 2010. Deposition of gold-titanium and gold-nickel coatings on electropolished 316L stainless steel bipolar plates for proton exchange membrane fuel cells. International Journal of Hydrogen Energy 35 1713-1718. 

Fig. 4 Long-term operation of identical metallic bipolar plates uncoated 316L, low-cost coating and gold plated. DANA standard conditions were as follows constant current operation at 250m cm , 80°C, fuUy humidified, anode stoichiometry 2, cathode stoichiometry 5...

Fig. 7 Contact/through-plate resistance of identical metallic bipolar plates with different coatings between two gas-diffusion layers. The uncoated, gold-coated, and graphite composite plates are included as references...

Figures 7 and 8 illustrate the results of a coating benchmark, which shows clear differences in performance and durability, which depend on the coating technique and composition. With different coatings the conductivity and durability of the metallic bipolar plate exceed the properties of a composite plate with comparable flow field. Diverse low-cost coatings (RNZ 05-06, RNZ 05-12, RNZ 05-13, and RNZ 05-16), which differ mainly in their canposition, highlight the necessity to control the chemistry and electrochemistry of the complete system of plate and coating. It was shown that with optimized coating composition (RNZ 05-16) it is possible to approximate the performance and durability of the gold-coated reference plate.

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