Corrosion Behavior of Stainless Steel Coated Graphene Layers for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates

Metallic materials such as stainless steel are considering as a bipolar plate for polymer electrolyte membrane fuel cells (PEMFCs) due to their low bulk electrical resistivity, high heat conductivity, high mechanical strength, gas impermeability, low cost, and ability to produce thin sheets or foil (0.1 - 1 mm thick) form to achieve high power densities [1]. However, its corrosion resistance in working conditions of PEMFCs is still far from satisfaction. In addition, metal ions produced during the corrosion process decrease the ionic conductivity of Nafion^®membrane and reduce the overall efficiency of a cell due to contamination of the catalysts [2]. Various coating materials such as ceramic-like nitride, carbides, conducting polymers, and surface modification of a substrate using thermal nitridation have been investigated to satisfy the requirements for bipolar plates [3]. Especially, carbon coating materials have received significant attention, because such materials supply excellent corrosion resistance, electrical conductivity and chemical stability in working conditions of PEMFCs [4]. In this study, carbon layers were coated on the surface of stainless steel plates to be used as bipolar plates in PEMFCs by spin coating system. Graphene oxide composite suspensions were used as coating materials. The graphene oxide layers were thermally reduced to increase the electrical conductivity. Microstructural analysis of the reduced graphene oxide layers were investigated by means of Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). For in-depth analysis of the corrosion properties, the electrochemical performance of the graphene coating layers was evaluated by the poteniodynamic method under simulated working conditions of PEMFCs, and the mechanism on corrosion resistance is discussed in detail.

References

[1] S.H. Lee, T.H. Tang, S.H. Hyun, Y.S. Yoon, Corros. Sci., 58 (2012) 79-85.

[2] S.H. Lee, V.E. Pukhac, V.E. Vinogradovc, N. Kakatia, S.H. Jee, S.B. Cho, Y.S. Yoon, Int. J. Hydrogen Energy, 38 (2013) 14284-14294.

[3] R. Taherian, J. Power Sources 265 (2014) 370-390.

[4] K. Feng, Z. Li, F. Lu, J. Huang, X. Cai, Y, Wu, J. Power Sources 249 (2014) 299-305.