NOVELTY - Solid alvelolar carbon monolith composite material with a hierarchical porous structure comprises macropores having average dimension dA of 1-100 mu m and micropores having an average particle size d1 of 0 7-1.5 nm; where the macropores and micropores are interconnected; and the material is free of mesoporous network and comprises nanoparticles of a metal M in the zero oxidation state, where the metal M is palladium and gold.    USE - The composite material is useful for producing dihydrogen, preferably for supplying hydrogen gas in a fuel cell operating at dihydrogen (claimed).    ADVANTAGE - The composite material has high surface area and hierarchical structure.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) preparing the composite material, comprising (i) impregnating a porous carbon monolith having a hierarchical porous network comprising macropores and micropores in a solvent, (ii) air drying the monolith, and (iii) subjecting the metal M nanoparticle to zero oxidation state by heat treating the monolith at 50-900 degrees C in the presence of a reducing gas, to cause reduction of the metal ion M until the zero oxidation;    (2) hydrogen storage method of a composite material comprising nanoparticles of metal M, comprising (a) degassing the material under high vacuum and at 150-400 degrees C, (b) at room temperature, impregnating the degassed in a solution containing at least one metallic hydride of formula (X(BH4)n) (I), (c) low vacuum drying the material impregnated with the metal hydride solution, at room temperature, and optionally (d) repeating one or more times, steps (b) and (c), in the solution, the organic solvent is ether;    (3) use of the composite material for producing dihydrogen;    (4) hydrogen production process using a composite material, comprising heating the composite material at 100 degrees C; and    (5) reversible method for producing dihydrogen implementing a composite material comprising a metal hydride (I), comprising: (i) heating the composite material at 100 degrees C to produce hydrogen gas, (ii) carrying out re-hydrogenation of composite material under hydrogen pressure of 50-200 bar at 200-500 degrees C for 1-48 hours, and (iii)repeating the steps (i) and (ii) one or more times.    X = Li, Na, Mg or K; and    n = 1, where if X = Li, Na or K, n = 2.