Strategy of alternating bias voltage on corrosion resistance and interfacial conductivity enhancement of TiCx/a-C coatings on metallic bipolar plates in PEMFCs

Proton exchange membrane fuel cells (PEMFCs) are deemed to be a promising renewable energy for variety of applications. However, metallic bipolar plates, one of key components in PEMFCs, still suffer from severe corrosion and degradation of interfacial conductivity under the humid and acid operating condition. Herein we proposed a novel strategy to enhance interfacial conductivity and corrosion resistance of TiCx/a-C coatings for metallic bipolar plates by alternating substrate bias voltage during the deposition process. The effects of the alternating substrate bias voltage strategy on the composition and morphology of the multilayered TiCx/a-C coatings had been explored. Both the corrosion resistance and the interfacial conductivity of the multilayered TiCx/a-C coatings were improved with more alternating periods of bias voltage. The effects of the enhanced performance had been discussed, and it was found that the alternating bias voltage strategy will restrain the columnar structures in the a-C layers and promote the generation of sp2-rich clusters on the surface. This versatile strategy based on moderately alternating cycles of substrate bias voltage exhibits great potential in many applications.