Nonisothermal and Isothermal Hydrogen Storage Behaviors of MgH2‐Based Composites Catalyzed by Carbon Isomeric Catalysts: Lightweight and Efficient Catalysis to Achieve High Capacity of Hydrogen Storage

Abstract

MgH2‐based composites are prepared by high‐energy ball milling surface catalysis with carbon isomeric catalysts to explore isothermal and nonisothermal H2 storage behavior. The reduction particle size and catalysts are conducive to absorption/desorption. The release peak temperatures of MgH2 catalyzed by activated carbon (AC), carbon nanotubes (CNTs), reduced graphene oxide (rGO), and expanded graphite (EG) are 445, 424, 458, and 446 °C, lower than that of MgH2 (≈463 °C). The hydrogenation capacities for the 3rd cycle of MgH2, MgH2–AC, MgH2–CNTs, and MgH2–EG are 3.35, 6.52, 6.66, and 6.92 wt%, corresponding to 47%, 90%, 92%, and 96% conversion rates. The dehydrogenation capacities increase to 5.86, 4.94, 3.18, and 5.74 wt% of MgH2–AC, MgH2–CNTs, MgH2–rGO, and MgH2–EG within 0.5 h, higher than MgH2 (2.29 wt%). The final dehydrogenation capacities of MgH2, MgH2–AC, MgH2–CNTs, MgH2–rGO, and MgH2–EG are 2.84, 6.69, 5.14, 3.65, and 6.61 wt%. The absorption capacities of MgH2, MgH2–AC, MgH2–CNTs, MgH2–rGO, and MgH2–EG within 0.5 h are 2.42, 6.47, 6.21, 3.03, and 4.20 wt%, and the final hydrogenation capacities reach 2.58, 6.65, 6.33, 3.10, and 4.34 wt%. The initial kinetics and the final degrees of absorption/desorption of MgH2 are elevated by carbon isomeric catalysts.