Development of Multilayered Coatings on Metal Plates with High Corrosion Resistance and Improved Electrical Conductivity by Plasma-Enhanced Chemical Vapor Deposition

The rapid growth of the proton exchange membrane fuel cell (PEMFC) market necessitates cost-effective and high-performance bipolar plates (BPs), which constitute a significant portion of the stack's weight and cost. While traditional graphite BPs are fragile and difficult to manufacture with precise flow channels, metallic BPs offer a promising alternative due to their superior mechanical properties and electrical conductivity. However, the corrosive operating environment of PEMFCs, characterized by high temperatures and acidic conditions, makes metallic BPs prone to corrosion, leading to performance degradation and reduced lifespan. Corrosion of BPs not only contaminates the catalyst layer but also impedes the electrical conductivity of the membrane electrode assembly. Various coating materials, including inert metals, transition metal nitrides, carbides, and carbon-based coatings, have been investigated to address this issue. However, the cost and performance limitations of these coatings necessitate further exploration of innovative solutions. This study focuses on the preliminary development of a novel approach utilizing plasma-enhanced chemical vapor deposition (PECVD) technology to deposit multilayered corrosion-resistant, electrically conductive, and durable coatings on metallic substrates. We report the successful development of an efficient PECVD reactor system and the optimization of deposition parameters for multilayered coatings comprising titanium (Ti), titanium carbide (TiCx), and amorphous carbon (a-C) on metal substrates. A safer and more environmentally friendly titanium precursor was identified and incorporated into the process, mitigating concerns about hazardous material (metal halides) during scaling. The resulting coatings were characterized using a variety of techniques, including Raman spectroscopy, X-ray diffraction (XRD), cross-sectional and surface scanning electron microscopy (SEM), as well as corrosion testing in acidic environments and thermal cycling tests. The coatings exhibited exceptional uniformity, high electrical conductivity, and promising corrosion resistance, meeting the demanding requirements for PEMFC applications.<br/>This innovative PECVD approach addresses critical performance bottlenecks in the fuel cell industry, enabling faster deposition rates and cost-effective fabrication of BPs that meet or exceed the performance targets of the US Department of Energy. The enhanced corrosion resistance, electrical conductivity, and durability offered by these multilayered coatings have the potential to revolutionize PEMFC technology, particularly in the rapidly expanding medium and heavy-duty vehicle sectors.