Hydrolysis H2 generation of Mg–Ni alloy catalyzed by expandable graphite/stannic oxide

In this work, Mg-10 wt% Ni (M) with higher theoretical hydrogen production is taken as the research object. M − 10C (M = Mg10Ni, C = EG (expandable graphite), SnO2 (stannic oxide), EG-SnO2) composites with various compositions were integrated by high-energy ball milling (HEBM), and their H2 production behavior in simulated seawater were investigated. Not only did X-ray analysis and scanning electron microscopy techniques be used to study the phase composition diffraction pattern and surface morphology of these Mg-based composites in detail, but also the performance and mechanism of hydrogen generation are investigated by initial hydrolysis kinetics. The results demonstrate that the addition of hollow SnO2 nanotubes and lamellar EG to the M alloy make surface loose and porous, and the existing cracks and gaps can increase hydrolysis channels with rapid medium transfer, thereby improving the initial reaction kinetics and the final hydrogen production rates. M − 10C (M = Mg10Ni, C = EG, SnO2, EG-SnO2) composites can produce 98.207, 69.996, 58.235 mL ⋅g−1 H2 within 15 s at 291 K, which are higher than M alloy without any catalyst (38.151 mL⋅g−1 H2). It is worth noting that M-10SnO2 rapidly release 395.4 mL⋅g−1 H2 with 51.35% yield in 2 min at 298 K. The difference between the H2 generation yields is mainly originated from the activity of catalysts on nucleation and growth of Mg(OH)2 in the hydrolysis reaction stage. Moderate initial nucleation rate and the subsequent sufficient growth of Mg(OH)2 nucleus are prerequisites to ensure fast initial hydrogen production rate and high H2 generation yield. Catalysis is an effective means to ameliorate the hydrogen performance of Mg-based alloys, and it is important to choose the appropriate catalyst type. However, the degree of catalysis determined by the content of the catalyst and the manner of addition is also worthy of attention.