Research on in situ temperature measurement and thermal stress simulation of proton exchange membrane fuel cell (PEMFC) based on thin-film thermocouples.

Proton exchange membrane fuel cells (PEMFCs) have attracted significant attention due to their advantages, including high energy density, rapid start-up, and environmental friendliness. However, as temperature fluctuations directly impact wettability, the rate of electrochemical reactions, and internal hydrothermal management, their performance is highly sensitive to operating temperature. This paper examines the preparation process and static calibration of thin-film thermocouples, as well as their application in the precise measurement of temperature and thermal stress simulation inside PEMFCs. First, based on the principle of the thermoelectric effect, this study adopted high-vacuum multifunctional magnetron sputtering technology to deposit NiCr and NiSi thin-film thermocouples with a thickness of ∼800 nm on the battery bipolar plate, sequentially on top of the SiO2 insulating film. Furthermore, a SiO2 protective layer was deposited to improve the device's environmental adaptability and mechanical stability. The static calibration results obtained using the Fluke calibration furnace system demonstrate that the sensitivity of the NiCr/NiSi thin-film thermocouple is 40.87 μV/°C. During the PEMFC temperature measurement experiment, real-time dynamic monitoring of the non-uniform temperature field during PEMFC start-up and operation was successfully achieved, with a peak temperature of 108.3 °C being measured during this period. In addition, to investigate the potential effects of complex thermal environments on the physical structure of the battery, this paper used simulation software to set up non-uniform temperature field conditions and constructed finite element simulation models of the bipolar plate and gas diffusion layer. The simulation results reveal that, due to significant differences in physical properties and thermal expansion coefficients between the bipolar plate and diffusion layer, the temperature gradient can lead to severe thermal stress concentration and regional displacement deformation within the battery's physical structure. This non-uniform thermomechanical deformation alters the pressure distribution at the contact interface and may induce risks such as physical tearing of the material, increased contact resistance, and leakage of reactive gases. Overall, this study provides a valuable scientific basis for optimizing the design of fuel cell structures, matching materials thermodynamically, and assessing the long-term stability of fuel cells.