Carbon corrosion in the catalyst is an important factor limiting the lifetime of proton exchange membrane fuel cells (PEMFCs). The water distribution inside the PEMFC directly determines the carbon support's corrosion rate in the catalyst. This study first investigates the water mole fraction distribution in the catalyst under different operating conditions, such as relative humidity (RH), temperature, pressure. It then divides the catalyst into different flooded areas according to the relationship between the water vapor partial pressure and saturated vapor pressure. Finally, it investigates the carbon corrosion characteristic of each region. The carbon corrosion of the catalyst is mainly divided into the corrosion in the non-flooded area and the corrosion in the flooded area. The results show that the decay rate of carbon support is around 4% after 5000 hours of operation in the non-flooding area. However, the degradation of the carbon support in the flooded area after 100 hours is as high as around 97.76%. Therefore, how to avoid flooding is the important issue that needs to be considered in the PEMFC. Moreover, increasing the pressure and RH promote the carbon corrosion in both cases, while increasing the temperature increases the carbon corrosion reaction rate, but it is beneficial to alleviate water flooding.

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