Abstract: A monopolar fuel cell stack comprising proton exchange membrane fuel cells supplied with a gaseous anodic reactant, preferably hydrogen, and a gaseous cathodic reactant, preferably air. The monopolar fuel cell stack, forming at least one substantially planar array, includes a liquid water retention barrier disposed over an electrode to retain liquid water within the fuel cells. The barrier is preferably used over the cathode side of each fuel cell and allows excess air flow to cool the fuel cell stack without drying the membrane in each fuel cell. The liquid water retention barrier may be either: (i) a thin, gas permeable, liquid water impermeable membrane; (ii) a thin, porous sheet of material; or (iii) a thin, substantially solid sheet of material except for a plurality of small through-holes that penetrate from one side of the sheet to an opposing side of the same sheet.

Abstract: A bipolar, filter press-like electrochemical cell stack comprising a plurality of electrochemical cells, where each electrochemical cell is supplied with a gaseous anodic reactant and either supplied with a gaseous cathodic reactant or produces a gaseous cathodic product, and where each electrochemical cell avoids drying out the ion exchange membrane polymer electrolyte, avoids flooding at the cathode, facilitates recovery of liquid water at the anode, and reduces water losses from at least one of the electrodes. A water retention barrier is variously positioned, such as between a gas diffusion electrode and a fluid flow field. The barrier may be either: (i) a thin, gas permeable, liquid water impermeable membrane; (ii) a thin, porous sheet of material; or (iii) a thin, substantially solid sheet of material except for a plurality of small through-holes that penetrate from one side of the sheet to an opposing side of the same sheet.