The magnesium hydrolyzing reaction was catalyzed in situ using a layered Mg2Ni compound, rapidly producing hydrogen in NaCl solution. The post-H-2 generation residue (mixture of Mg(OH)(2) and Mg2Ni 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/Mg2Ni/Mg/Mg2Ni... layered structure, in which each layer was similar to 0.8 gm thick; Mg was an anodic phase and Mg2Ni was a cathodic phase (the catalyst). Bulk Mg/Mg2Ni 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 similar to 36.35 kJ mol(-1). Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.