Ultraefficient Catalysis of NiO/Ni(OH)2 for Hydrogen Generation via Mg Hydrolysis

Active metal hydrolysis is favored for safety and environmental friendliness in the field of hydrogen generation. In practice, however, dense oxide/hydroxide films form instantaneously on the metal surface; these passivating layers act as electronic insulators that severely curtail charge transfer and, consequently, suppress hydrogen evolution. Herein, a novel heterostructure of NiO/Ni(OH)2 was designed to enhance the electron transfer rate in the magnesium powder hydrolysis system, achieving rapid hydrogen production. Surprisingly, Mg-2 wt % NiO/Ni(OH)2 achieved a near 100% conversion rate, producing 880.2 mL g–1 of H2 in only 20 s at 30 °C. Its maximum hydrogen generation rate (mHGR) surpassed that of pure magnesium by 35-fold, and such hydrolysis performance is superior to all the reported results of catalyzed-Mg systems so far. Theoretical studies confirmed that the space charge region in NiO/Ni(OH)2 affects the electronic structure; thus, the correspondingly generated built-in electric field accelerated the hydrolysis of magnesium and greatly facilitated the electron transfer of the system. This work provides a strategy for designing nickel-based oxides/hydroxides catalysts for light metal hydrolysis and facilitates the understanding of the catalytic mechanism in multiphase catalytic systems.