TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Component: The controller is configured such that the relative humidity exceeds 150, preferably 300% without humidity regulation elements within the device downstream of the diffusion media and prior to the humidified reactant output. It regulates a relative humidity of the first or second reactant inputs such that the relative humidity of the humidified reactant output exceeds 150%. It regulates temperature, pressure, humidity, and flow rates of the first and second reactant inputs such that the relative humidity of the humidified reactant output exceeds 150%. The device also includes a structure defining a vehicle powered by the fuel cell.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The hydrophilic carbonaceous component comprises a low surface area carbon having a surface area of 60-80 m2/g. The hydrophilic carbonaceous component comprises a major portion of the low surface area carbon and a minor portion of carbon graphite in addition to the low surface area carbon. It comprises a low surface area carbon having a mean particle size of 42 nm. It comprises carbon black, graphite, carbon fibers, carbon fullerenes, and/or carbon nanotubes, preferably acetylene black having a surface area of 60-80 m2/g.Preferred Composition: The mesoporous layer comprises 90-95 wt.% carbonaceous component.Preferred Property: The mesoporous layer defines a thickness of less than 15, most preferably 10-12 microns. It partially infiltrates the diffusion media substrate, preferably to a depth of less than 5 microns. It has porosity greater than a porosity of the fibrous matrix of the diffusion media substrate.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The hydrophilic carbonaceous component comprises a low surface area carbon having a surface area of 60-80 m2/g. The hydrophilic carbonaceous component comprises a major portion of the low surface area carbon and a minor portion of carbon graphite in addition to the low surface area carbon. It comprises a low surface area carbon having a mean particle size of 42 nm. It comprises carbon black, graphite, carbon fibers, carbon fullerenes, and/or carbon nanotubes, preferably acetylene black having a surface area of 60-80 m2/g.Preferred Composition: The mesoporous layer comprises 90-95 wt.% carbonaceous component.Preferred Property: The mesoporous layer defines a thickness of less than 15, most preferably 10-12 microns. It partially infiltrates the diffusion media substrate, preferably to a depth of less than 5 microns. It has porosity greater than a porosity of the fibrous matrix of the diffusion media substrate.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The hydrophobic component comprises a fluorinated polymer consisting of polytetrafluoroethylene, polyvinylidene fluoride, and/or polyvinyl fluoride.    TECHNOLOGY FOCUS - TEXTILES AND PAPER - Preferred Material: The substrate comprises carbon fiber paper having a porosity above 80%, a thickness of 100-300 microns, and a mean pore size above 25 preferably 25-35 microns.