Properties of NbC/а-C:H films on titanium bipolar plates for proton exchange membrane fuel cells

Surface modification of metallic bipolar plates is a crucial subject for the performance elevation of proton exchange membrane fuel cells (PEMFCs). In this work, a series of NbC/а-C:H films with different Nb/C ratios are prepared by arc ion plating. Film microstructure, composition, mechanical properties, hydrophobility, interfacial contact resistance (ICR), and corrosion resistance in the simulated cathode environment of PEMFCs are systematically studied. The results show that within the experiment conditions, higher NbC content helps to promote the film hardness and adhesion strength as well as the interfacial conductivity. While higher а-C:H content attributes to a more compact microstructure thus improving the anti-corrosion performance. The best corrosion resistance and conductivity come with the lowest corrosion current density of 0.09 µA/cm² and ICR of 0.77 mΩ cm², respectively. Based on the result of this research, to further improve the comprehensive performance of NbC/а-C:H film, strategies for increasing the metal carbide content and preventing surface metal oxidation while keeping a dense and fine microstructure need to be considered.