氢燃料电池金属双极板表面TiC/a-C:H涂层的制备和表征

Preparation and characterization of TiC/a-C: H coating on the surface of metal bipolar plates in hydrogen fuel cells

摘要:

目的 研究沉积离子能量对沉积在氢燃料电池金属双极板表面的TiC/a-C:H涂层导电性和耐腐蚀性能影响。方法 通过磁过滤真空阴极弧沉积技术以Ti靶为Ti源,通入乙炔气体在-100~-500 V基体负偏压下于SS 304不锈钢和单晶硅表面沉积了厚度为0.52~1.05 μm的TiC/a-C:H复合涂层,研究分析了涂层的微观结构、涂层成分、相结构、耐腐蚀性能和导电性能的变化规律。结果 在-100~-500 V基体负偏压下沉积的TiC/a-C:H复合涂层均呈现致密的低缺陷特征,涂层为非晶碳包覆的nc-TiC纳米晶所构建的纳米晶/非晶复合结构,随着负偏压增大,涂层中纳米晶尺寸从3.3 nm增至7.9 nm。最优的nc-TiC/a-C:H涂层(负偏压-100 V)在模拟氢燃料电池腐蚀环境(80℃, 0.5 mol/L H₂SO₄+2 ppm HF 水溶液)下实现了0.0525 μA/cm₂^{的超低腐蚀电流密度},在1.4 MPa的压紧力下实现了1.49 mΩ/cm₂^的极低ICR值。结论 采用磁过滤真空阴极弧沉积法制备的nc-TiC/a-C:H涂层可以在宽的负偏压范围内有效提高SS 304不锈钢双极板的耐腐蚀和导电性,满足DOE 2025目标对氢燃料电池双极板的性能需求,该工作为大规模制备高性能金属双极板涂层开辟了一条新途径。

Abstract:

Filtered cathodic vacuum arc deposition has an ultra-high ionization rate (nearly 100%), which can effectively suppress micro defects in the coatings optimize the microstructure of the coatings, and improve the performance of the coatings. In response to the poor corrosion resistance of metal bipolar plates in hydrogen fuel cells and their tendency to dissolve in acidic environments during long-term operation of proton exchange membrane fuel cells , we used a filtered cathodic vacuum arc deposition process to deposite a series of high conductivity and strong corrosion resistant nc-TiC/a-C: H coatings on the surface of metal bipolar plates in proton exchange membrane fuel cells In this paper, the effects of deposited ion energy on the conductivity and corrosion resistance of TiC/a-C: H coatings deposited on the surface of metal bipolar plates in hydrogen fuel cells were investigated. Nc-TiC/a-C: H nanocomposite coatings with a thickness of 0.52-1.05 μm were deposited on the surfaces of SS 304 stainless steel and monocrystalline silicon at negative substrate bias voltages of -100~-500 V with acetylene gas flow rate of 30 sccm by a dual bend filtered cathodic vacuum arc deposition process. The phase structure of the coatings were analyzed using X-ray diffraction (X pert pro MPD); The cross-section and surface microstructures of the coatings were characterized by field emission scanning electron microscopy (S-4800, Hitachi); Observation of high-resolution morphology of coatings using transmission electron microscopy (FEI CM200, Philips); The chemical element composition and chemical bond structure of the coating were analyzed by X-ray photoelectron spectroscopy (ESCALAB 250Xi, Thermofish); Raman spectroscopy (LavRAM Aramis, Horiba Jobin Yvon) characterizes the chemical structure distribution of carbon elements in the coating; The electrochemical workstation (IM6ex, Zahner elektrik) evaluated the corrosion resistance of coatings under simulated hydrogen fuel cell operating conditions. The surface contact resistance tester tested the contact resistance under different pressures; The study analyzed the changes in microstructure, coating composition, phase structure, corrosion resistance, and conductivity of TiC/a-C: H coatings under different negative bias voltages. The results show that the TiC/a-C: H composite coatings deposited under negative bias voltage of -100~-500 V exhibit dense low defect characteristics. The coatings are nanocrystalline/amorphous composite structure constructed by amorphous carbon coated nc-TiC nanocrystals. As the negative bias voltage increases, the size of nanocrystals in the coating increases from 3.3 nm to 7.9 nm. The optimal nc-TiC/a-C: H coating (coating deposited at negative bias -100 V) achieved an ultra-low corrosion current density of 0.0525 μA/cm_² in a simulated hydrogen fuel cell corrosion environment (80 ℃, 0.5 mol/L H₂SO₄+2 ppm HF aqueous solution), and achieved an extremely low ICR value of 1.49 mΩ/cm_² under a compression force of 1.4 MPa. Our results show that the nc-TiC/a-C:H coatings prepared by filtered cathodic vacuum arc deposition process can effectively improve the corrosion resistance and conductivity of SS 304 stainless steel bipolar plates within a wide negative bias range, meeting the performance requirements of DOE 2025 target for hydrogen fuel cell bipolar plates. This work open up a new avenue for the large-scale preparation of high-performance metal bipolar plate coatings.