Corrosion-resistant and interfacial conductive AlTiVCrMo high-entropy alloy and (AlTiVCrMo)N_x high-entropy ceramics coatings for surface modification of bipolar plates in proton exchange membrane fuel cells

Metal bipolar plates (BPPs) are candidates with great promise to replace conventional carbon-based BPPs. However, the drawbacks caused by the corrosion and passivation of metal bipolar plates need to be addressed urgently. In present study, corrosion-resistant and interfacial conductive high-entropy alloy and ceramic coatings possess great potential in the application of surface modification of bipolar plates in proton exchange membrane fuel cells (PEMFCs). An original co-filtered cathodic vacuum arc deposition (C-FCVAD) is designed to prepare AlTiVCrMo high-entropy alloy (HEA) and (AlTiVCrMo)N_x high-entropy ceramic (HEC) coatings with different nitrogen content, and their feasibility as surface modification methods of bipolar plates is investigated by analyzing the microstructure, corrosion properties, interfacial conductivity and hydrophobicity of the coatings. The obvious body-centered cubic (BCC) structure can be observed in HEA coating, and amorphous structure is gradually formed as the nitrogen content increases to 28.12 at. %. Finally, polycrystal structure is formed when nitrogen content reached the maximum. The electrochemical corrosion and interfacial contact resistance (ICR) results significantly demonstrate that the coatings have enhanced corrosion resistance and conductivity. The bipolar plates with AlTiVCrMo HEA and (AlTiVCrMo)N_x HEC coatings as surface modification methods have good application potential in PEMFCs operating environment.