TECHNOLOGY FOCUS - POLYMERS - Preferred Membrane: The membrane comprises pores which are partially or totally occluded to gases. The membrane having pores which are totally occluded to gases, contains (in weight%) ionomer (more than 30). The membrane having pores which are partially occluded to gases, contains ionomer (less than 20). The membrane comprises amorphous or crystalline (per)fluoropolymers.Preferred Support: The porous support is made of (per)fluoropolymers, preferably polytetrafluoroethylene, more preferably bistretched polytetrafluoroethylene.Preferred Ionomer: The ionomer is (per)fluorinated polymer having SO3H and COOH groups, preferably SO3H. Especially the ionomer comprises a monomer unit (A) having fluorinated monomer(s) with ethylene unsaturation(s), and fluorinated monomeric unit (B) containing functional groups transformable into hydrophilic groups such as SO2 and/or group of formula COR, COF. The functional groups are converted to hydrophilic groups. Especially, the ionomer comprises monomeric units derived from tetrafluoroethylene, monomeric unit of F2C=CF-O-CF2-CF2SO2F, monomeric unit of bisolefin, and iodine atoms at end position. The amorphous ionomer shows residual crystallinity of less than 5%, preferably less than 1%. The (per)fluorinated ionomers are crosslinked. The perfluoropolymers are of crystalline ionomeric type.Preferred Monomers: The fluorinated monomers (A) are selected from vinylidene fluoride, 2-8C perfluoroolefin (preferably tetrafluoroethylene), 2-8C chloro and/or bromo and/or iodofluoro olefins (such as chlorotrifluoroethylene and bromotrifluoroethylene), (per)fluoroalkyl vinyl ethers of formula CF2=CFORf, and perfluoro-oxyalkylvinylether of formula CF2=CFOX.R = 1-20C alkyl or 6-20C aryl;Rf = 1-6C (per)fluoroalkyl such as trifluoromethyl, bromo difluoromethyl and pentafluoropropyl;X = 1-12C perfluorooxyalkyl having ether group(s), such as perfluoro-2-propoxy propyl.The fluorinated monomer (B) is selected from F2C=CF-O-CF2-CF2SO2F, F2C=CF-O-(CF2-CXF-O)n-CF2-CF2-SO2F, F2C=CF-O-CF2-CF2-CF2-SO2F, F2C=CF-Ar-SO2F, F2C=CF-O-CF2-CF2-CF2-COF, and F2C=CF-O-(CF2CXF-O)nCF2-CFX-COF.Ar = aryl ring;X = Cl, F or CF3;n = 1-10.The ionomer contains monomeric unit (0.01-5) derived from bisolefin represented by formula: R1R2C=CH-(CF2)m-CH=CR5R6.R1, R2, R5, R6 = H or 1-5C alkyl;m = 2-10, preferably 4-8.Preferred Process: The impregnated support is washed with water until neutral pH of washing water is obtained. The ionomer is cross-linked by adding cross-linking agent to impregnation solution. The ionomer is cross-linked at 100-300degreesC by adding peroxide to impregnation liquid.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Fuel Cell: The fuel cell containing the membrane, comprises air pressure at cathode side which is higher than that of hydrogen at anode side. The feed hydrogen obtained from reforming contains carbon monoxide. EXAMPLE - (In ml) demineralized water (850), monomer of formula CF2=CF-O-CF2CF2-SO2F (74 g), a compound of formula CF2ClO(CF2CF(CF3)O)n(CF2O)mCF2COONH4 (240) (n/m = 10), solution of transfer agent of formula I-C(F2)6-I (13), and solution of bis-olefin of formula CH2=CH-(CF2)6-CH=CH2 (2), were stir-mixed, and heated. Aqueous solution of ammonium persulfate (APS) (50) was fed, and reacted. The pressure was maintained at 6 absolute atm by feeding tetrafluoroethylene (TFE). Monomer of formula CF2=CF-OCF2CF2-SO2F (19 g) and solution of bis-olefin (2) were added, and reacted. The latex produced was coagulated, and the polymer was separated from the mother liquor and dried. The ionomer formed was amorphous. (In g) obtained ionomer (1.32) was dissolved in methylperfluorobutylether to form ionomer solution.    A porous polytetrafluoroethylene membrane was impregnated in the ionomer solution, and the ionomer solution was deposited on both sides of the membrane. The membrane was heated. Then cross-linking agent was deposited on each side of the membrane, and heated. The cross-linking of the membrane was performed. The membrane was treated in aqueous potassium hydroxide solution, washed and treated in aqueous hydrogen chloride solution, and again washed. Then the membrane was dipped in demineralized water and dried. The membrane comprised ionomer (26 mg). The membrane was transparent at dry state. The membrane had Gurley number of greater than 10000 s and water permeability of 25 l/(h.m2.atm).