NOVELTY - The method comprises: combusting a solid pyrotechnic charge hydrogenated gas generator (7) for producing a hydrogen-containing gas having at least 70 mole% of hydrogen; supplying a portion of hydrogen-containing gas into a thermal machine (2); and relaxing a portion of the hydrogen-containing gas output from the machine at a pressure of less than or equal to 5.105 Pa and then cooling to a temperature of less than 200 degrees C, and supplying a cooled hydrogen-containing gas to a fuel cell (3). The method further comprises filtering produced hydrogenated gas before supplying to the machine to remove solid residues.    USE - The method is useful for supplying a hydrogenated gas to a fuel cell (claimed) such as an on-board or portable fuel cell used in aeronautical industry.    ADVANTAGE - The method is capable of supplying the hydrogenated gas to the fuel cell in an energy-efficient manner thus improving energy density, stability and lifespan of the fuel cell.    DETAILED DESCRIPTION - The method comprises: combusting a solid pyrotechnic charge hydrogenated gas generator (7) for producing a hydrogen-containing gas having at least 70 mole% of hydrogen; supplying a portion of hydrogen-containing gas into a thermal machine (2); and relaxing a portion of the hydrogen-containing gas output from the machine at a pressure of less than or equal to 5.105 Pa and then cooling to a temperature of less than 200 degrees C, and supplying a cooled hydrogen-containing gas to a fuel cell (3). The method further comprises: filtering the produced hydrogenated gas before supplying to the machine to remove the solid residues; filtering the hydrogenated gas discharged by the machine, before supplying to the fuel cell, to partially remove the solid residues; and purifying the hydrogenated gas in the upstream of the fuel cell to remove the poisons gas species. The pyrotechnic charge comprises a solid pyrotechnic product including 25-45 wt.% of inorganic oxidizing component and 55-75 wt.%, preferably more than 70% of reducing component. An INDEPENDENT CLAIM is included for a device for supplying the hydrogenated gas to the fuel cell.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a device for supplying the hydrogenated gas to the fuel cell.    Combustion chamber (1)    Thermal machine (2)    Fuel cell (3)    Particle filter (4)    Solid pyrotechnic charge hydrogenated gas generator. (7)