Sealing body plays the role of support and seal in fuel cell, and the attenuation of sealing body will lead to the problems of stack leakage, leakage, assembly pressure relaxation, contact resistance change and so on, which will lead to the failure of stack performance reduction, life acceleration attenuation, hydrogen leakage safety, insulation disqualification and so on.

In summary, the main requirements of fuel cell sealant are as follows:

1) Air tightness: Air leakage will affect the performance of the fuel cell;

2) Acid resistance: the pH value of sulfonic acid group in proton exchange membrane in fuel cell is 1-2, and the pH value of water generated by electrochemical reaction is 3-5[8].

3) moisture resistance: the electrochemical reaction will have water generation, is a high humidity environment, sealing materials should have moisture resistance;

4) Temperature resistance: the operating temperature of the fuel cell stack is generally between 60℃ and 90℃, and the cold start temperature is -40℃;

5) Low precipitation amount: the sealing material will gradually age and degrade during the use process, and the precipitates (such as metal ions, fillers, sealant degradation particles, etc.) will not cause problems such as proton exchange membrane aging, catalyst poisoning, gas diffusion layer micropore blockage and so on;

6) Mechanical properties: the sealing material should have the effect of shock absorption and impact resistance, and the compression amount should be able to compensate the thickness tolerance of membrane electrode, bipolar plate and other components in the manufacturing process, and will not lead to overpressure or insufficient pressure of membrane electrode components.

Some literatures suggest that silica gel is not suitable for long life reactor. In the simulated solution (12 μg/g H2SO4 and 1.8μg/ GHF), the chemical corrosion resistance of silicon rubber is obviously lower than that of fluorine silica gel and EPDM rubber, and in the actual situation, the degradation of silicon rubber is obvious. However, it is true that some fuel cell manufacturers use silicone rubber as sealing material, and their stack life has reached tens of thousands of hours. This contradiction is undoubtedly worth paying attention to.