Michael Hirscher1,2
Max Planck Institute for Intelligent Systems1,Advanced Institute for Materials Research, Tohoku University2
Michael Hirscher1,2
Max Planck Institute for Intelligent Systems1,Advanced Institute for Materials Research, Tohoku University2
Hydrogen storage in nanoporous materials has been attracting a great deal of attention in recent years, as high gravimetric H<sub>2</sub> capacities can be achieved at 77 K using materials with particularly high surface areas. Cryogenic storage by physisorption of hydrogen molecules will safely operate at low pressures, is fully reversible and has fast kinetics.<br/>Experimental data of the gravimetric and volumetric hydrogen uptake have been analysed for many MOFs showing a linear correlation of the gravimetric absolute uptake with the specific surface area (Chahine’s rule) [1]. Using the packing density of the powder as well as the single-crystal density, a linear relation is found between the volumetric absolute hydrogen uptake and the volumetric surface area [2]. The specific total volume occupied by a porous material, i.e. the inverse of its packing or single crystal-density, as a function of its specific surface area yields a linear relationship. Based on these results, a phenomenological model is developed for the volumetric absolute uptake as a function of the gravimetric absolute uptake [2]. The key for improving the volumetric storage capacity is closing the gap between the low-density powder towards the theoretical upper limit of the single crystal by either compaction, pelletizing or monoliths. Furthermore, interpenetrated frameworks show generally higher volumetric hydrogen uptakes [3]. Finally, for technical applications the key parameter is the usable or working capacity, which is the amount of hydrogen that can be delivered between the maximum tank pressure and the back pressure required by the end-user [4].<br/>The presentation will give an overview of the current status and discuss future concepts [5,6].<br/> <br/><b>References</b><br/>[1] M. Schlichtenmayer, M. Hirscher, <i>J. Mater. Chem</i>. 22, 10134 (2012)<br/>[2] R. Balderas-Xicohténcatl et al., <i>Energy Te</i><i>chnol</i>. 6, 578 (2018)<br/>[3] R. Balderas-Xicohténcatl et al., <i>Energy Technol</i>. 6, 510 (2018)<br/>[4] M. Schlichtenmayer, M. Hirscher, <i>Appl Phys A</i> 122, 379 (2016)<br/>[5] D.P. Broom et al., <i>Int. J. Hydrogen Energy</i> 44, 7768 (2019)<br/>[6] L. Zhang et al., <i>Progress in Energy</i> in press (2022)