Graphene composite coating for enhanced corrosion resistance of Ni foam flow field in PEMFC

With the development of proton exchange membrane fuel cells (PEMFCs), metal foam with lightweight advantages and highly porous structures has become promising flow field material to replace traditional carbon plates. However, in the operating environment with high temperatures and acid situation, it suffers severe corrosion issues. To solve this problem, Sn and Sn/graphene composite coatings are prepared and the physical characteristics are analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Tafel polarization test, potentiostat test, and electrochemical impedance spectroscopy are used to test the corrosion resistance of coated nickel foam in a PEMFC cathodic environment. Compared to Sn-coated foam, the corrosion resistance is further enhanced with the addition of graphene. The Sn/graphene coating obtained by electrodeposition at current density of 15 mA & sdot;cm-2 has the lowest corrosion current density, which accounts for only 41.20 % and 33.48 % of the uncoated foam value at 50 degrees C and 80 degrees C, respectively. It also exhibits the maximum coating resistance, the lowest potentiostatic current and interfacial contact resistance, which is 66.3 % lower than the US DOE 2025 goal. After an 8 h constant potential test, no noticeable pitting behavior is shown on the surface because of the compact Sn/graphene coating. The addition of graphene promotes the nucleation of Sn metal and results in lower Sn oxidation.