As stated in Section 4.3, the chann

As stated in Section 4.3, the channels between clusters become narrower at lower water contents, in accordance with the membrane cluster-network model [23]. The decrease inwater content caused cracking of some channels and disrupted the movement of hydronium ions, thus decreasing the ionic conductivity of the membrane. The decreasing water content in the membrane thus decreased the electro-osmotic drag coefficient and membrane conductivity. Under these conditions, the smaller electroosmotic drag coefficient was advantageous for water management in the PEM fuel cell. However, in contrast, the decreased membrane ionic conductivity reduced the performance of the fuel cell. Therefore, PEM fuel cells should be operated under conditions allowing for better hydration of the membrane [14]. Vengatesan et al. [25] proposed the use of a thin-cast membrane to properly maintain the membrane ionic conductivity by manipulating the water back-diffusion phenomenon. Thus, the PEM fuel cell performance can be improved.