Argon ion gun-assisted magnetron sputtering of multilayer graded TiN for proton exchange membrane fuel cell bipolar plates: Enhanced conductivity and corrosion resistance

The optimization of metallic bipolar plate coatings is crucial for proton exchange membrane fuel cells (PEMFCs). In this study, a nitrogen graded TiN coatings were deposited on stainless steel substrates via magnetron sputtering, where the integration of an argon ion gun intensified the ion bombardment on the growing film and significantly enhanced their conductivity and corrosion resistance. Scanning electron microscope (SEM) and atomic force microscope (AFM) analyses revealed that the introduction of the argon ion gun resulted in smoother and denser coating surfaces, attributed to the ion bombardment during deposition that effectively mitigated shadowing effects. Electrochemical tests further demonstrated superior performance, with the coatings exhibiting a corrosion current density of (Formula presented) and an interfacial contact resistance (ICR) of about (Formula presented). After corrosion, the ICR remained below (Formula presented), meeting the United States Department of Energy (DOE) 2025 targets. Additionally, the TiN coatings displayed improved hydrophobicity, evidenced by a markedly increased water contact angle, which facilitates effective water management during fuel cell operation. By enabling cost-effective manufacturing and enhanced durability of TiN-coated stainless steel bipolar plates, this work underscores the transformative potential of argon ion gun-assisted magnetron sputtering in accelerating the commercialization of PEMFC technology for automotive and grid-scale energy applications.