The frequency of pulsed DC sputtering power introducing the graphitization and the durability improvement of amorphous carbon films for metallic bipolar plates in proton exchange membrane fuel cells

Amorphous carbon (a-C) films have been coated on the metallic bipolar plates (BPPs) in Proton Exchange Membrane Fuel Cells (PEMFCs) to improve the corrosion resistance and the interfacial electrical conductivity of metallic BPPs. However, the durability of a-C in the harsh environments of PEMFCs is still confronted with enormous challenges. In this paper, a-C films are prepared on SS316L BPPs via pulsed DC sputtering power with different frequency and the further understanding of corresponding mechanism on the structure and the performance of a-C is revealed. The results indicate that the compactness of films is enhanced significantly by pulsed DC power. Moreover, the moderate frequency is beneficial to the formation of nanographite clusters, which are embedded into a-C and reduce the interfacial contact resistance (ICR). Furthermore, the analyses of corrosion performance of the films conclude that the embedded nanographite clusters form micro primary cell with a-C and protect a-C from corrosion. The ICR of the film prepared at 200 kHz after corrosion for 200 h at 0.84 V-vs.SHE is 2.44 m Omega.cm(2), which exhibits ultra-low ICR and achieves excellent durability during the operating procedures of PEMFCs. This study is beneficial to enhance the lifetime of a-C and promote the commercialization of PEMFCs.