Enhanced hydrogen generation performance of CaMg2-based materials by ball milling

Abstract

Non-catalytic hydrolysis of CaMg₂-based materials (abbreviated as CaMg₂, CaMg₂–0.1Ni, H-CaMg₂, and H-CaMg₂–0.1Ni hereinafter) fabricated by ball milling for hydrogen supply has been investigated in the present work. With respect to the as-melted counterparts, it is found that both milled CaMg₂ and H-CaMg₂-based samples can significantly enhance the hydrolysis performance via adjusting the milling durations. In particular, 0.5 h-milled CaMg₂ and 3 h-milled H-CaMg₂ exert optimal kinetics at ambient temperature, delivering a hydrogen yield of 539 mL g⁻¹ within 2 h and 1439 mL g⁻¹ of H₂ within only 3 min, respectively. In addition, the further results indicate that the hydrogen uptake of CaMg₂ can be accelerated by doping with the Ni element, giving rise to considerably enhanced hydrolytic dynamics, as opposed to a limited promotion of the hydrolysis of the CaMg₂ alloy. For example, the hydrogen yield of H-CaMg₂–0.1Ni increases from 853 to 1147 mL g⁻¹ H₂ in 5 min with hydrogenation durations ranging from 0.5 to 1.5 h, much higher than the values (598–954 mL g⁻¹ H₂) of H-CaMg₂ under the same conditions. More specifically, the 3 h-milled H-CaMg₂ sample also demonstrates excellent cryogenic hydrolysis kinetics, achieving a hydrogen yield of 1332 mL g⁻¹ H₂ within 15 min at 0 °C. In comparison with the conventional hydrogenation of pristine CaMg₂ conducted at elevated temperature, a more feasible strategy is applied to realize its hydrogen uptake by ball milling with Ni under mild conditions. Expectedly, the hydrogen supply capacities of the hydrogenated samples are markedly enhanced, making them promising to achieve their wide applications in hydrogen energy areas in the future.