Cr/A-C Films for Stainless Steel Bipolar Plates in Pemfcs: Insights into Nano Interlock Microstructure, Deposition Parameters, and Performance Optimization

Stainless steel SS bipolar plates, crucial components in proton exchange membrane fuel cells (PEMFCs), face limitations such as increased interfacial contact resistance (ICR) and corrosion in acidic, humid conditions. The research underscores the influence of deposition parameters, specifically biased potential and processing temperatures, on film characteristics. Higher biased potential enhances microstructures beneficial for bipolar plate surfaces, improving electrical conductivity, corrosion resistance, and hydrophobic properties. However, elevated deposition temperatures, while enhancing surface performance, lead to a hard carbide phase, compromising bonding strength and overall film quality. The study highlights the importance of nanocrystalline grain sizes in the Cr interlayers, with reduced sizes achieved through increased biased potential or processing temperatures resulting in decreased ICR and corrosion current density. Nano-interlocked structures within Cr/a-C gradient regions contribute to enhanced corrosion resistance. Moreover, obtuse-angled structures at the Cr-a-C interface further improve film performance by impeding micro-defect initiation and growth during deposition. In summary, this research provides crucial insights into tailoring Cr/a-C films for SS bipolar plates, addressing challenges in PEMFCs, and optimizing film characteristics for improved performance.