In addition to the molecular diffusion and electro-osmotic drag, water is generated in the cathode catalyst layer due to electrochemical reaction.1) Electro-osmotic drag fluxElectro-osmotic water flux through the membrane can be calculated from the proton flux through the membrane, given by the specified promotion info current density and Faraday lawJH2O=2��ndI(x,y)2F:Electro?osmotic drag flux(7)where nd is Electro-osmotic drag coefficient which depends on water activity as follows.nd=0.0029��2+0.05��?3.4��10?19(8)where �� represents water contend of the membrane described as,��=0.043+17.81aK?39.85aK2+36.0aK3,0