Shucheng Sun

Comparative Study of PEM Fuel Cell Storage at − 20 ° C after Gas Purging

The effect of water removal and freeze/thaw cycles on proton exchange membrane (PEM) fuel cells was investigated by comparative study of 20 on/off and freeze/thaw cycles after purging by reactant gas with relative humidity 58.0% at 25°C. Within 20 cycles, the cell performance, electrochemical active surface areas, and electrochemical impedance spectra responses were analyzed by the mean squared deviation method. No performance decay caused by water freezing was observed, and the water amount in the cell was reduced to an extent by which freeze degradation was avoided.

Behaviors of a proton exchange membrane electrolyzer under water starvation

Water starvation could be one of the reasons for proton exchange membrane (PEM) water electrolyzer degradation. In this paper, the water starvation phenomena of a unit cell in a PEM electrolyzer stack are investigated. The voltage, current density and temperature distribution are investigated in situ with a segmented electrolyzer. The results show that the voltage of the middle and outlet regions is higher than the inlet voltage, which illustrates that water starvation could occur simultaneously in different regions of the electrolyzer. The water stoichiometries have an important effect on the voltage distribution, current density distribution and temperature distribution at 0.5 A cm−2 and 60 °C. The electrochemical impedance spectra of different segments show that the cell resistance and charge transfer resistance gradually increase along the water flow direction when the water stoichiometry is 3. According to the flow regime map, the critical water stoichiometry for electrolysis is further discussed.