However, since the anode gets highl

However, since the anode gets highly humidified by back transport, it is not possible for the anode to have a positive concentration gradient at any point across the membrane and electrode with respect to the cathode as the amount of product water produced at any time is always higher than what is back transported, even at the oxygen inlets. Thus the areas of osmotic drag and back transport cannot be segregated to inlet and outlet regions. Thoughthe rate of back diffusion may vary at the inlet and outlet, the rate will be high at the oxygen outlet. The regions in the membrane where osmotic drag and back diffusion takesplace can be interpreted from ion clustering in Nafion membranes. One series of studies postulates the existence of sizable regions, of dimensions of ca. 50 A, in which the ionsare clustered [16]. Through this large number of tiny islands of ion cluster, osmotic drag takes place wherever there is more proton transport, and in other regions back diffusiontakes place. Since the fluorinated back bone is highly water repellent, no water transport is expected in those regions