Abstract
Cryogenic adsorption using microporous materials is one of the emerging technologies for hydrogen storage in fuel cell vehicles. Metal–organic frameworks have been identified as suitable adsorbents exhibiting large hydrogen sorption at 77 K. With respect to technical realization, in this work, the deliverable capacity at the optimal storage temperature was determined for a series of MOFs in comparison to zeolite Ca-A. The deliverable capacity is defined as the amount of hydrogen released between a maximum tank pressure and a minimum back pressure and shows a maximum which defines the optimum operating temperature. This optimum operating temperature depends on the pore size of the adsorbent and the chemical properties of the surface. A number of materials are identified that exhibit optimal operating temperatures well above 100 K. A higher optimal storage temperature, however, typically results in a lower deliverable capacity.
Highlights
Hydrogen is regarded as a promising alternative energy vector for fossil fuels
Many technologies to store hydrogen are currently investigated [1]. These technologies vary from pressurized vessels over liquid storage to chemical storage in hydrides [2,3,4] or liquid organic hydrogen carriers (LOHC) [5,6,7]. Another large field of interest is the adsorptive storage of hydrogen in porous materials such as activated carbons [8,9,10], zeolites [11, 12], porous polymers [13], and metal–organic frameworks (MOFs) [14, 15]
Tedds et al calculated the deliverable capacity in the pressure range between 2 and 15 bar for different MOFs, zeolites, and carbons [22]
Summary
Hydrogen is regarded as a promising alternative energy vector for fossil fuels. many technologies to store hydrogen are currently investigated [1]. Tedds et al calculated the deliverable capacity in the pressure range between 2 and 15 bar for different MOFs, zeolites, and carbons [22] They showed that the highest sorption capacity is not always found at 77 K and that the temperature dependency is different depending on the material investigated. Schlichtenmayer and Hirscher investigated the temperature-dependent sorption swing of several members of the DUT family in comparison with activated carbons and several other MOFs [24] and showed that the optimum operating temperature is influenced by the enthalpy of adsorption In this contribution, we present hydrogen sorption isotherms of several porous materials and calculated their different deliverable H2 capacity behavior. We show that it is feasible to calculate the deliverable capacity from measurement at three different temperatures (77, 195, and 273 K) in good agreement to experiments where many temperatures were used
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