Multilayered Zr–C/a-C film on stainless steel 316L as bipolar plates for proton exchange membrane fuel cells

Abstract

A multilayered zirconium-carbon/amorphous carbon (Zr–C/a-C) coating is synthesized by magnetron sputtering in order to improve the corrosion resistance and interfacial conductivity of stainless steel 316L (SS316L) as bipolar plates for proton exchange membrane fuel cells (PEMFCs). Zr–C/a-C film contains an outmost pure amorphous carbon layer and a sub zirconium containing carbon layer. Interfacial contact resistance (ICR) between carbon paper and coated SS316L decreases to 3.63 mΩ cm2 at 1.4 MPa. Potentiodynamic polarization results reveal that the corrosion potential of Zr–C/a-C coated sample is more positive than pure a-C coated sample and the current density is only 0.49 μA cm−2 at the cathode applied potential 0.6 V. Electrochemical impendence spectroscopy also indicates that multilayered Zr–C/a-C film coated SS316L has much higher charge transfer resistance than the bare sample. After potentiostatic polarization, ICR values are 3.92 mΩ cm2 and 3.82 mΩ cm2 in the simulated PEMFCs cathode and anode environment, respectively. Moreover, XPS analysis of the coated samples before and after potential holding tests shows little difference, which disclose the chemical stability of multilayered Zr–C/a-C film. Therefore, the multilayered Zr–C/a-C coating exhibits excellent performance in various aspects and is preferred for the application of stainless steel bipolar plates.