Corrosion-resistant nanostructured carbon-based coatings for applications in fuel cells based on bipolar plates

Abstract

The paper reports on carbon coatings deposited by accelerated C60 ion beam irradiation onto the VT1-0 titanium alloy surface at different substrate temperatures, considering potential applications in fuel-cell bipolar plates. We identified the temperature range for forming a conductive carbon nanocomposite coating (CNC) at different accelerating voltages (Ua). The obtained CNC consists of graphite nanocrystals embedded in an amorphous diamond-like matrix. The nanocomposite containing ∼40% of sp3 bonds is formed at Ts = 300–400 °C under Ua = 6 kV. The increase in accelerating voltage to 8 kV reduces the temperature of the nanocomposite formation to Ts = 200 °C. Interface contact resistance (ICR) of a CNC coated titanium plate decreases to 2.6 ± 0.7 mOhm⋅cm2 at a sealing pressure of 1.5 MPa, which is close to carbon paper – graphite contact resistance. This low ICR value persists after prolonged corrosion tests. Tribological studies established high wear resistance and high adhesion of CNC to titanium substrate, showing potential for stable operation of coated bipolar plates in mobile applications. CNC allows to overcome the limitation of corrosion-caused ICR increase, which makes CNC-coated titanium a promising candidate to substitute gold-coated stainless steel as a raw material for bipolar plates of proton-exchange membrane fuel cells.