MoC İnce Film Kaplamaların Pem Tipi Yakıt Hücreleri İçin Korozyon Direnç Performansların Araştırılması

Abstract

In this thesis study, the performance of molybdenum carbide (MoC) thin film coating developed to enhance the corrosion resistance of bipolar plates (BPs), a crucial component of proton exchange membrane (PEM) fuel cells was examined in detail within the context of hydrogen technologies, which play a critical role in the search for sustainable energy solutions in light of the finite nature and environmental impacts of fossil fuels. PEM fuel cells stand out as environmentally friendly, high efficiency energy conversion systems, with widespread applications in automotive and portable power systems. BPs account for 80 % of the stack’s total mass and 45 % of its cost, underscoring their importance. These plates must exhibit excellent electrical and thermal conductivity, low gas permeability, and high corrosion resistance. Although BPs are typically made from graphite, its brittleness and difficulty of machining have led to the adoption of metallic materials particularly stainless steel (SS). However, metallic BPs are prone to corrosion in the perfluorosulfonic-acid and electrochemical environment of PEM cells, which degrades fuel cell performance. To address this issue, protective and conductive surface coatings are applied to the BPs. In this context, the development of coating materials that are highly conductive, corrosion resistant, and cost-effective is of great importance. MoC is recognized as a good corrosion-resistant material due to its low cost, high melting point, thermal stability, hardness, and high conductivity. Therefore, MoC emerges as a potential candidate for enhancing the corrosion resistance of bipolar plates used in PEM fuel cells. In this work, MoC thin films were deposited onto SS, Si, and soda lime glass (SLG) substrates using two different techniques: a hybrid method combining magnetron sputtering with plasma enhanced chemical vapor deposition (PECVD), and a magnetron co-sputter method. While films produced by the hybrid method exhibited structural defects, those prepared by the magnetron co-sputter technique met the U.S. Department of Energy’s (DOE) standards by improving the corrosion resistance of the BPs. MoC thin film coated SS plates demonstrated a 50% improvement in ICR compared to uncoated SS plates. Furthermore, potentiodynamic polarization measurements revealed a very low corrosion current density of 5.813 × 10⁻⁷ A·cm⁻². This value is approximately one order of magnitude lower than the target set by the U.S. Department of Energy (DOE) (<1 × 10⁻⁶ A·cm⁻²), indicating that the DOE target was successfully achieved. These results demonstrate that MoC thin-film coatings offer innovative solutions to the corrosion challenges encountered in fuel-cell technologies and introduce materials-engineering approaches capable of revolutionizing the energy sector.films produced by the hybrid method, those prepared via the magnetron co-sputter method significantly enhanced the corrosion resistance of the bipolar plates, surpassing DOE standards. It was determined that stainless steel (SS) plates coated with MoC thin films exhibited a 50% improvement in ICR values compared to uncoated SS plates, and potentiodynamic polarization measurements yielded a very low corrosion current density of 5.813 × 10⁻⁷ A·cm⁻². These results demonstrate that MoC thin film coatings offer innovative solutions to the corrosion challenges encountered in fuel cell technologies and reveal materials engineering approaches that could revolutionize the energy sector.