NOVELTY - A direct oxidation fuel cell system comprises fuel source, direct oxidation fuel cell, fuel evaporative mechanism (142), fuel delivery assembly, and load. The direct oxidation fuel cell includes membrane electrode assembly, anodic diffusion or backing layer, and cathodic diffusion or backing layer. The membrane electrode assembly includes membrane electrolyte (118) and catalyst layer. The membrane electrolyte is conductive to hydroxide anions, is electronically non-conductive, and has opposing anode (120) and cathode (116) faces.    USE - A direct oxidation fuel cell system used in portable electronics.    ADVANTAGE - The system incorporates a cathode backing layer which minimizes water loss in vapor form at the cell cathode while facilitating oxygen transport to cell cathode; incorporates an air-breathing cathode which achieves a completely passive operation of the vapor feed direct hydrocarbon alkaline fuel cell (VFDHAFC) without any auxiliary equipment for fuel supply to the cell anode, for air supply to the cell cathode, for water balance, and for thermal balance; incorporates an air-breathing cathode that when reinforced with air fan or air pump to enhance air supply to the cell cathode, better performance and high power density of VFDHAFC are expected; allows performance of VFDHAFC to be insensitive to its orientation along with gravity; allows VFDHAFC power systems to be operated and stored at a sub-zero environmental temperature (as low as - 93.9 degrees C with neat methanol) without suffering freezing damage; allows adjustments to the fuel concentration i.e. fuel is added only as it is consumed, thus problems associated with methanol crossover and water carryover are reduced due to limiting of feeding into the system; has a simplified CO2 removal by providing direct ventilation after its generation at the fuel cell anode; has a low production cost by using non-noble metal based catalyst while achieving the needed fuel cell performance and conversion efficiency; has low potentially hazardous exposure of the corrosive electrolyte to end user.    DETAILED DESCRIPTION - A direct oxidation fuel cell system comprises fuel source, direct oxidation fuel cell, fuel evaporative mechanism (142), fuel delivery assembly, and load. The direct oxidation fuel cell includes membrane electrode assembly, anodic diffusion or backing layer, and cathodic diffusion or backing layer. The membrane electrode assembly includes membrane electrolyte (118) and catalyst layer. The membrane electrolyte is conductive to hydroxide anions, is electronically non-conductive, and has opposing anode (120) and cathode (116) faces. The catalyst layer is disposed in intimate contact on each of anode and cathode faces such that anodic electrooxidation of fuel and hydroxide anions into carbon dioxide (CO2, 179), water, and electrons occurs, and such that cathodic electrooxidation of an oxygen source into electrons, water, and oxygen also occurs. The anodic diffusion or backing layer is disposed in intimate contact with anode catalyst layer, and has opening and paths for associated fuel to pass through. The cathodic diffusion or backing layer is disposed in intimate contact with cathode catalyst layer, and has opening and paths for oxygen to pass through. The fuel evaporative mechanism is disposed between fuel source and anodic diffusion layer such that fuel in the form of vapor passing through from anodic diffusion layer to anode catalyst layer is vented from the fuel cell, and such that evolution of CO2 during fuel consumption at the anode catalyst layer is also vented from the fuel cell. The fuel delivery assembly is coupled between fuel source and fuel evaporative mechanism. The load is coupled across fuel cell and providing a path for electrons which generates electricity as electrolysis proceeds. The system further comprises a mechanism for driving off moisture produced at cathode backing layer. INDEPENDENT CLAIMS are included for:    (1) a fuel cell (having the specified membrane electrode assembly) operable by feeding the cell anode with a hydrocarbon fuel vapor from a neat hydrocarbon fuel or a solution of highly concentrated hydrocarbon fuel and water at greater than or equal to 1:1 mole ratio, and by feeding the cell cathode with air or oxygen in either passive or forced flow;    (2) a liquid form of neat hydrocarbon fuel or a aqueous solution of highly concentrated hydrocarbon fuel being stored in an enclosed space and being separated from methanol vapor by an evaporating membrane or other porous medium, where anode compartment containing both liquid hydrocarbon fuel and fuel vapor can be completely sealed from atmospheric air during operation;    (3) removal of CO2 gas generated at the cell anode catalyst layer during cell operation by allowing permeation of CO2 gas through membrane electrode assembly to reach cell cathode and then released to atmospheric air, where one specific route is through the porous nature of anionic hydroxide conducting material;    (4) placement of pinholes between the cell anode and the evaporating membrane to allow release of CO2;    (5) a positive pressure build-up at the anode compartment for facilitation of water movement from the cell anode where it is generated to the cell cathode where it is consumed; and    (6) utilization of varied hydrophobocity including highly hydrophobic anode backing layer and highly hydrophilic cathode catalyst layer for facilitation of water movement from the cell anode where it is generated to the cell cathode where it is consumed.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of fuel feed and carbon dioxide transportation through the membrane and ventilation at the cell cathode.    Cathode (116)    Membrane electrolyte (118)    Anode (120)    Fuel evaporative mechanism (142)    Carbon dioxide (179)