ZIF-8 Pellets as a Robust Material for Hydrogen Cryo-Adsorption Tanks

Area of Science:

• Materials Science
• Chemical Engineering
• Energy Storage

Background:

• Cryoadsorption in porous materials is a key strategy for hydrogen storage.
• Zeolitic imidazolate frameworks (ZIFs) are stable, porous materials suitable for this application.

Purpose of the Study:

• To evaluate the hydrogen storage capacity of ZIF-8 synthesized via mechanochemical twin-screw extrusion.
• To assess the impact of pelletization on ZIF-8's volumetric hydrogen storage.

Main Methods:

• Mechanochemical synthesis of ZIF-8 powder and pellets using twin-screw extrusion.
• Hydrogen storage capacity measurements at 77 K and up to 100 bar across multiple labs and setups.
• Cycling experiments to evaluate material stability.

Main Results:

• Pelletizing ZIF-8 enhanced packing density without porosity loss, improving volumetric storage.
• High reproducibility in hydrogen uptake measurements was confirmed.
• A temperature-pressure swing adsorption process yielded approximately 31 g of usable hydrogen per liter of pellet.
• No degradation in storage capacity was observed after cycling experiments.

Conclusions:

• ZIF-8 pellets exhibit excellent stability and high volumetric hydrogen storage capacity.
• Mechanochemically synthesized and pelletized ZIF-8 is a promising material for technical hydrogen storage applications.
• The material's robustness supports its use in pilot- and full-scale adsorption vessels.