Microstructure and hydrogen generation performance via hydrolysis of as-cast Mg-Ca-Ni and Mg-Ca-Sn ternary alloys

Mg is a promising in-situ hydrogen generation material due to the advantages of high hydrogen generation capacity and low cost. Aiming at exploring as-cast Mg alloys with fast hydrolysis kinetics and high conversion rate, Mg-8Ca-xNi (x = 0, 0.6, 1.1, 2.1, wt.%) and Mg-12Ca-ySn (y = 1, 2, 3, wt.%) alloys have been fabricated via solidification in this work. The phase constituent, microstructure and hydrogen generation performance of as-cast Mg-Ca-Ni/Sn alloys have been investigated systematically. Microstructures consisting of primary Mg and eutectic mixtures are observed in both Mg-Ca-Ni and Mg-Ca-Sn ternary alloys. As-cast Mg-Ca-Ni ternary alloys show superior hydrolysis kinetics and almost 100 % hydrolysis conversion rate in simulated seawater. Primary Mg crystals are severely corroded by simulated seawater within initial 10 s with the promotion action of Mg2Ni, arising abundant cracks. Mg-8Ca-2.1Ni alloy generates ∼915.4 mL g−1 H2 within 470 min at 20 °C. Matrix activity, optimized microstructure of alternately distributed Mg, Mg2Ca and Mg2Ni phases, and water solution transport assisted by cracks account for the complete hydrolysis of as-cast Mg-Ca-Ni alloys. In contrast, as-cast Mg-Ca-Sn ternary alloys show inferior hydrolysis performance. As-cast Mg-12Ca-2Sn alloy shows a maximum hydrogen yield of ∼542.1 mL g−1 within 720 min at 60 °C.