These are the proton and electro-osmotic transports, the water generation resulted by the electrochemical reaction, the water diffusion and convection. Water diffusion arises due to a water concentration difference be tween the cathode side and the anode side. Usually thecathode has a higher water concentration caused by water formation as a result of the chemical reaction between H and O2. The electro-osmosis (often called electro-osmotic flux or water drag) is caused by the conjugated transport of the water molecules with the protons in the electric field: the water molecules mainly move in the protons’ solvation shells. Theconvective flux of water is caused by a pressure gradient