Development and characterization of multilayered Cr–C/a-C:Cr film on 316L stainless steel as bipolar plates for proton exchange membrane fuel cells

Multilayered chromium–carbon/amorphous carbon:chromium (Cr–C/a-C:Cr) is deposited on 316L stainless steel (SS316L) sheet as bipolar plates for proton exchange membrane fuel cells (PEMFCs) using closed field unbalanced magnetron sputter ion plating (CFUBMSIP). Raman spectra and X-ray diffractometry (XRD) indicate that the Cr–C/a-C:Cr film is composed of amorphous carbon, metallic Cr phase, chromium carbide phases. The stactic water contact angle of the film reaches 89.1°. Interfacial contact resistance (ICR) between the coated SS316L sheets and carbon paper is only 2.89 mΩ cm2 at 1.5 MPa. Potentiodynamic tests in the simulated corrosive circumstance of PEMFCs reveals that the corrosion potential of coated samples is 0.236V vs SCE and the passivation current density is 0.276 μA cm−2 at 0.6 V in simulated cathodic environment. A single cell with Cr–C/a-C:Cr coated SS316L bipolar plates is assembled and tested to evaluate the in-situ performance of the film. The peak power density of the single cell is 1278.2 mW cm−2 at a current density of 2674.1 mA cm−2. Compared to a-C coating developed in our previous work, the performance of Cr–C/a-C:Cr coating is improved in various aspects and Cr–C/a-C:Cr coated SS316L bipolar plates are more practically applied for commercialization of PEMFCs technology.

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► Cr–C/a-C:Cr film is deposited on SS316L sheet as bipolar plates using CFUBMSIP.
► Contact resistance is 2.89 mΩ cm−2 at 1.5 MPa and contact angle reaches 89.1°.
► The passivation current density is 0.276 μA cm−2 at 0.6 V in cathodic environment.
► Single cell with coated bipolar plate achieves peak power density of 1278.2 mW cm−2.