Fig. 5b shows that the polarization

Fig. 5b shows that the polarization curves of the PEMFC shift upwards as temperature increases from 20 ◦C to 60 ◦C under control of the cooling water. This phenomenon indicates the improvement of electrical efficiency as temperature increases. It can be explained in that the rise of the temperature increases proton mobility in the membrane and improves catalyst activity and gas diffusion [42]. A much higher temperature is beneficial for the PEMFC to reduce inner resistance and improve electrical performance. However, according to the experimental data, it can also be concluded that the influence of temperature is limited, the voltage having only a marginal improvement above the temperature of 60 ◦C. This is because of drying of the membrane and increase in internal resistance. In regard to the durability and life of the PEMFC, thermal management is required to maintain its temperature below 70℃.