NOVELTY - Making a proton-conducting membrane (38) involves: (a) combining a protonated, layered inorganic material with a proton-conducting organic polymer in a liquid medium; (b) exfoliating the layered inorganic material, so that layers of the inorganic material are suspended in the liquid medium and spaced from each other; and the polymer is absorbed onto the surface of the layers, to form a polymer-inorganic composite; and (c) removing substantially all of the liquid, and forming the polymer-inorganic composite into a membrane.    USE - As a proton-conducting membrane, useful in an electrolysis device comprising steam electrolysis device (preferably electrically-powered electrolytic cell) useful for producing hydrogen electrolytically by steam electrolysis; and proton exchange membrane (PEM) fuel cell (claimed). The PEM fuel cells are useful in automobiles.    ADVANTAGE - The proton-conducting membranes exhibit a thermal stability greater than the prior art membranes i.e. are stable at above 180 degrees C, along with a conductivity that permits their use in various electrochemical devices, such as proton exchange membrane (PEM) fuel cells and steam electrolysis systems; as compared to the prior art membranes formed from conventional protonated materials such as perfluorinated sulfonated polymers without an inorganic constituent that typically break down at more than 120 degrees C. As compared to the electrolytic cells with prior art membranes that are not suitable for steam electrolysis system at above 100 degrees C; the production of hydrogen using electrolytic cell comprising electrodes separated from each other by the proton-conducting membrane, allows steam electrolysis to be carried out at 180-300 degrees C. The ability to carry out electrolysis at these temperatures close to optimum range of 140-350 degrees C allows the process to operate more efficiently to generate electricity and economically because steam or waste heat from various power generation sources can rapidly bring the electrolyzer up to proper operating temperatures. Thus, the cost of external heating is minimized or eliminated. As a result, clean steam which is discharged from a nuclear power plant can be used to bring an electrolyzer up to operating temperature, e.g. through the use of heat exchangers. Also, waste heat from the nuclear plant can be used to boil water, to producing more steam for an electrolyzer system. Further, steam originating from a geothermal source at these higher temperature can also be utilized as part of an electrolyzer systems to provide hydrogen as end-product, or store the hydrogen for other purposes e.g. hydrogenation. In addition to ability to produce hydrogen at higher temperatures, the proton-conducting membrane containing electrolyzers avoids need to carry out hydrolysis in a very corrosive environment i.e. alkaline hydrolysis including potassium hydroxide, at pH of 14; which can damage to various fittings and connections in an electrolysis bath, while also decreasing over-potential to form oxygen at one of the electrodes; and exhibits ability to run electrolysis at higher temperatures in relatively pure water which increases efficiency, and also minimizes wear-and-tear on the process hardware.    DETAILED DESCRIPTION - Making a proton-conducting membrane (38) involves: (a) combining a protonated, layered inorganic material with a proton-conducting organic polymer in a liquid medium; (b) exfoliating the layered inorganic material, so that layers of the inorganic material are suspended in the liquid medium and spaced from each other; and the polymer is absorbed onto the surface of the layers, to form a polymer-inorganic composite; and (c) removing substantially all of the liquid, and forming the polymer-inorganic composite into a membrane. The inorganic material is protonated by ion exchange technique that involves contacting inorganic material with acidic, hydrogen-containing material, under heat treatment conditions which cause hydrogen protons to replace substantially all metal cations present in the inorganic material. The exfoliation of the layered inorganic material is carried out by agitation of the liquid medium, so that at least some of the layers of the inorganic material spread apart from each other and become dispersed within the liquid medium, and/or separate into sublayers. The agitation of liquid medium is carried out by sonication. The liquid medium is a colloid; and comprises a water-miscible, functionalized solvent (preferably functionalized with sulfone groups) in which the proton-conducting polymer is soluble. The proton-conducting polymer is thermally stable at greater than or equal to 80 degrees C. The exfoliated inorganic layers have an average thickness of less than 500 nm. The layered inorganic material and the polymer are collapsed after exfoliation in step (b) by centrifuging, and/or pH adjustment, so that the layers are brought into relatively close, substantially parallel contact with each other; and at least a portion of the polymer is sandwiched between individual inorganic layers. Alternatively, the layered inorganic material is exfoliated, prior to combining with the proton-conducting organic polymer. At least one dimension of the exfoliated inorganic layers is on a nanoscale, and the membrane comprises a nanocomposite material. INDEPENDENT CLAIMS are included for the following:    (1) a proton-conducting membrane comprising: cured polymer matrix in which inorganic material comprising hydrous silicate material is dispersed, where the inorganic material is in the form of exfoliated layers; and polymer chains of the polymer matrix are disposed between the exfoliated layers;    (2) electrolysis device or a proton exchange membrane (PEM) fuel cell comprising: two electrodes electrically connected to each other through power supply, in which each electrode is separated from the other electrode by the proton-conducting membrane; and    (3) method for producing hydrogen electrolytically from steam by steam electrolysis involving: directing steam from a steam source comprising steam discharges from a nuclear power plant or steam emissions from a geothermal source, to at least the anode (32) of an electrically-powered electrolytic cell (30) comprising two electrodes electrically connected to each other through a power supply; and separated from each other by the proton-conducting membrane, such that electrical activation of the cell causes the electrolytic dissociation of water in the steam, so that hydrogen is generated within the cell.    DESCRIPTION OF DRAWING(S) - The figure shows electrolysis system comprising the proton-conducting membrane.    Steam electrolysis system (30)    Anode (32)    Cathode (34)    Steam (35)    Plate structure (37)    Proton-conducting membrane. (38)