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

Abstract

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 2.73×10−6Ωm and an interfacial contact resistance of 16.65mΩcm2. 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 4h. 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.