Comparison study on C–Cr and a-C coatings on titanium plates for PEMFCs applications via midfrequency magnetron sputtering

Aiming to develop the property of bipolar plates for proton exchange membrane fuel cells (PEMFCs), we investigate the properties of amorphous carbon (a-C) coatings and chromium-doped amorphous carbon (C–Cr) coatings onto titanium by midfrequency dual-cathode magnetron sputtering. In the simulated cathode environment of PEMFCs, the corrosion potential (Ecorr) for C−Cr coating is improved compared with uncoated protected Ti. Moreover, the corrosion current density (Icorr) decreases from 18.4 to 0.298 μA/cm2, meeting the United States Department of Energy 2025 index requirements. The interfacial contact resistance obviously decreases after chromium doping of a-C coating (2.98–3.44 mΩ cm2) in comparison with the original (5.58–74.92 mΩ⋅cm2), suggesting that chromium doping dramatically improves the coating properties and can be used in PEMFCs. The study also finds that the water contact angle increases from θmin = 62.65° on the uncoated surface to θmax = 87.91° on the C−Cr surface, indicating better water management of the stack.