Production of an Mg/Mg2Ni lamellar composite for generating H2 and the recycling of the post-H2 generation residue to nickel powder

The magnesium hydrolyzing reaction was catalyzed in situ using a layered Mg 2 Ni compound, rapidly producing hydrogen in NaCl solution. The post-H 2 generation residue (mixture of Mg(OH) 2 and Mg 2 Ni catalyst) was recycled to recover pure Ni powder from the waste mixture. Pure Mg (153 g) and pure Ni (47 g) in a eutectic composition were easily melted to form a molten alloy by a super-high-frequency (35,000 Hz) induction furnace. The lamellar material had an Mg/Mg 2 Ni/Mg/Mg 2 Ni… layered structure, in which each layer was ∼0.8 μm thick; Mg was an anodic phase and Mg 2 Ni was a cathodic phase (the catalyst). Bulk Mg/Mg 2 Ni composite alloy contains many microgalvanic cells. Owing to the lamellar microstructure, no dense hydrated oxide film that might have caused surface passivation was found, allowing continuous H 2 generation until no magnesium remained to participate in the hydrolysis. The activation energy of the hydrolysis reaction in simulated sea water was ∼36.35 kJ mol −1 .