The back-diffusion process further

The back-diffusion process further helps to distribute water more evenly across the membrane, a mechanism that is well known from the literature, and lower the overall membrane’s resistivity. Since the amount of water to be circulated within the membrane is mainly determined by the incoming water from inlet anode humidification, the membrane’s resistivity,and hence ohmic overpotential, becomes highly susceptible to the variation of inlet relative humidity at anode. Therefore, for each matrix’s element in Fig.4, fully humidified anode always gives rise to the smallest ohmic overpotential and hence the maximum deliverable power density. This is supported by the plots of water content and ohmic overpotential in Fig.6.