Fig. 3 presents the relative humidi

Fig. 3 presents the relative humidity profile along the channel at the anode and cathode sides. The relative humidity decreased along the channel at the anode side, while it increased at the cathode side at all operating temperatures and pressures studied. The water removal at the gas inlets increased at higher temperatures and pressures; thus, the relative humidity of the inlet gas decreased faster. The decrease in the amount of water in the inlet gas also resulted from the condensation rate, electro-osmotic drag and friction between the gas streams in the rib of the flow field. The increase in relative humidity at the cathode side was due to the presence of water generated by the electrochemical reaction and the movement of water from the anode side by electro-osmotic drag. The consumption of oxygen along the channel also contributed to the increase in the mole fraction of water. The decrease in the oxygen mole fraction along the channel was higher when the relative humidity at the cathode was lower for fully saturated inlet gas at the anode, in accordance with the results of a previous study