The present invention relates to an electrochemical cell having the separator assembly that comprises a fluid distribution means comprising wicking material on the cathode side of a membrane electrode assembly (MEA). The wicking material transports liquids internally within the fuel cell; promotes humidification of the membrane; and provides a self-regulating cooling system for the fuel cell. The wicking material further forms gas flow channels for introducing gases to and from the MEA. Other preferred aspects of the present invention include methods of cooling the fuel cell by evaporation and/or vaporization at the cathode side.