Effect of deposition temperature on columnar structure of α-C nano-coatings of PEMFC metal bipolar plates

Amorphous carbon (α-C) nano-coatings are the most commonly used coating materials for the metal bipolar plates in fuel cells due to their low cost, excellent electrical conductivity, and good corrosion resistance. However, α-C usually forms a columnar structure during the deposition process, which seriously affects its performance and service life. This study proposes that the columnar structure of α-C nano-coatings can be controlled by modifying the deposition temperature during magnetron sputtering. Further, the effects of deposition temperature on the composition, microstructure, electrochemical corrosion behavior, interfacial conductivity and hydrophilicity of α-C nano-coatings were systematically studied. The results show that the columnar structure of α-C nano-coatings is inhibited by increasing the deposition temperature. When the deposition temperature is above 300 °C, the microstructure of the α-C nano-coatings changes from columnar to denser microcrystalline. At the same time, a higher deposition temperature leads to a higher proportion of sp2 carbon in the α-C nano-coatings; resulting in significant improvement in the corrosion resistance, interfacial conductivity and hydrophobicity of the coatings.