Nanoporous adsorbents for hydrogen storage

Abstract

Hydrogen storage in absorbents as activated carbons has been rarely investigated; however, about 25 years ago, the development of new nanomaterials, initiated by Iijima’s discovery of carbon microtubules, started new hopes. Unfortunately, initial results on high hydrogen uptake in carbon nanotubes at ambient conditions could not be independently reproduced; however, at cryogenic conditions, these novel nanomaterials just behaved as activated carbons with an uptake proportional to the surface area. Shortly after, the development of coordination polymers with permanent porosity opened a new route to nanoporous materials with ultra-high internal surfaces. Mainly metal–organic frameworks (MOFs) have been attracting a great deal of attention in recent years, as very high gravimetric hydrogen capacities can be achieved at 77 K. Cryogenic storage by physisorption of hydrogen molecules will safely operate at low pressures, is fully reversible, and possesses fast kinetics. This mini-review shows the rapid development in this field over the past 25 years. Exemplarily, the main focus is on results obtained in the hydrogen storage laboratory in Stuttgart and their connection to Applied Physics A.