Architecting periodic nitride multilayers for highly robust proton exchange membrane water electrolysis bipolar plates

Proton exchange membrane water electrolysis requires bipolar plate coatings that combine high electrical conductivity with robust corrosion resistance under strongly acidic and oxidative conditions, yet these properties are often mutually exclusive. Herein, a periodic TiN/NbN multilayer coating is fabricated by pulsed laser deposition to overcome this conductivity-corrosion trade-off through interfacial architecture engineering. The resulting multilayer coating exhibits an ultralow corrosion current density of 0.0096 μA cm−2 and a low interfacial contact resistance of 8.0 mΩ cm2 under a compressive pressure of 1.5 MPa, fully meeting U.S. DOE targets for bipolar plates. Compared with monolithic TiN coatings, the periodic TiN/NbN multilayer delivers more than one order of magnitude improvement in corrosion resistance while maintaining efficient electronic transport. Microstructural analyses reveal that alternating nitride layers suppress columnar defect propagation and act as diffusion barriers against anodic oxidation. First-principles calculations further demonstrate pronounced interfacial charge redistribution at the TiN/NbN heterointerface, enhancing atomic bonding stability and stabilizing conductive pathways under high anodic polarization. This work establishes periodic nitride multilayers as an effective interfacial design strategy for highly stable and conductive PEMWE bipolar plates under simulated anodic conditions.