Effects of metal buffer layer for amorphous carbon film of 304 stainless steel bipolar plate

Amorphous carbon (a-C) films comprising different buffer layers were prepared by direct current magnetron sputtering on a 304 stainless steel (SS) substrate surface. Microstructures and performances of a-C films with buffer layers comprising Ti, Cr and W were investigated and evaluated as bipolar plate for proton exchange membrane fuel cell (PEMFC). All prepared a-C films are graphite-like carbon, and predeposition of the buffer layer promote the graphitization of the a-C film. The a-C film comprising a Cr buffer layer has highest percentage of sp2 hybridization contents, which directly improved the current conductivity with a resistivity of 2.73 × 10− 6 Ω m and an interfacial contact resistance of 16.65 mΩ cm2. Furthermore, dynamic polarization under a simulated PEMFC working environment shows that the corrosion resistance greatly improved. The corrosion current density of an a-C film with a Cr buffer layer stabilizes at a negative value after potentiostatic tests for 4 h. The hydrophobic property is improved as well, which is beneficial to water management in PEMFC and for anticorrosion of the bipolar plate itself. Thus, the metal buffer layers make the a-C film more suitable for surface modification of a 304 SS bipolar plate, especially the a-C film with a Cr buffer layer.