Rapid and efficient hydrogen clathrate hydrate formation in confined nanospace

Clathrate hydrates are crystalline solids characterized by their ability to accommodate large quantities of guest molecules. Although CH4 and CO2 are the traditional guests found in natural systems, incorporating smaller molecules (e.g., H2) is challenging due to the need to apply higher pressures to stabilize the hydrogen-bonded network. Another critical limitation of hydrates is the slow nucleation and growth kinetics. Here, we show that specially designed activated carbon materials can surpass these obstacles by acting as nanoreactors promoting the nucleation and growth of H2 hydrates. The confinement effects in the inner cavities promote the massive growth of hydrogen hydrates at moderate temperatures, using pure water, with extremely fast kinetics and much lower pressures than the bulk system.We would like to acknowledge financial support from Ministerio de Ciencia e Innovación (Project PID2019-108453GB-C21), MCIN/AEI/10.13039/501100011033 and EU “NextGeneration/PRTR” (Project PCI2020-111968 /3D-Photocat) – JSA. Neutron scattering experiments were performed at ORNL’s Spallation Neutron Source, IPTS-27062, supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, US DOE, under Contract No. DE-AC0500OR22725 with UT Battelle, LLC—J.S.A., Y.Q.C., L.D., A.J.R.C.. We gratefully acknowledge research support from the Hydrogen Materials—Advanced Research Consortium (HyMARC), established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technology Office, under Contract Number DE-AC05-00OR22725—R.B.-X. This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The publisher acknowledges the US government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan)

Establishing ZIF-8 as a reference material for hydrogen cryoadsorption: An interlaboratory study

Hydrogen storage by cryoadsorption on porous materials has the advantages of low material cost, safety, fast kinetics, and high cyclic stability. The further development of this technology requires reliable data on the H2 uptake of the adsorbents, however, even for activated carbons the values between different laboratories show sometimes large discrepancies. So far no reference material for hydrogen cryoadsorption is available. The metal-organic framework ZIF-8 is an ideal material possessing high thermal, chemical, and mechanical stability that reduces degradation during handling and activation. Here, we distributed ZIF-8 pellets synthesized by extrusion to 9 laboratories equipped with 15 different experimental setups including gravimetric and volumetric analyzers. The gravimetric H2 uptake of the pellets was measured at 77 K and up to 100 bar showing a high reproducibility between the different laboratories, with a small relative standard deviation of 3–4 % between pressures of 10–100 bar. The effect of operating variables like the amount of sample or analysis temperature was evaluated, remarking the calibration of devices and other correction procedures as the most significant deviation sources. Overall, the reproducible hydrogen cryoadsorption measurements indicate the robustness of the ZIF-8 pellets, which we want to propose as a reference material.M. Maiwald, J. A. Villajos, R. Balderas and M. Hirscher acknowledge the EMPIR programme from the European Union's Horizon 2020 research and innovation programme for funding. F. Cuevas and F. Couturas acknowledge support from France 2030 program under project ANR-22-PEHY-0007. D. Cazorla and A. Berenguer-Murcia thank the support by PID2021-123079OB-I00 project funded by MCIN/AEI/10.13039/501100011033, and “ERDF A way of making Europe”. K. N. Heinselman, S. Shulda and P. A. Parilla acknowledge the support from the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technology Office through the HyMARC Energy Materials Network

Selective Hydrogen Isotope Separation via Breathing Transition in MIL-53(Al)

Breathing of MIL-53(Al), a flexible metal-organic framework (MOF), leads to dynamic changes as narrow pore (np) transitions to large pore (lp). During the flexible and reversible transition, the pore apertures are continuously adjusted, thus providing the tremendous opportunity to separate mixtures of similar-sized and similar-shaped molecules that require precise pore tuning. Herein, for the first time, we report a strategy for effectively separating hydrogen isotopes through the dynamic pore change during the breathing of MIL-53(Al), a representative of flexible MOFs. The experiment shows that the selectivity for D2 over H2 is strongly related to the state of the pore structure of MIL-53(Al). The highest selectivity (SD2/H2 = 13.6 at 40 K) was obtained by optimizing the exposure temperature, pressure, and time to systematically tune the pore state of MIL-53(Al)

Efficient synthesis for large-scale production and characterization for hydrogen storage of ligand exchanged MOF-74/174/184-M (M = Mg2+, Ni2+)

A semitechnical route (optimized by BASF SE) to synthesize MOF-74/174-M (M = Mg2+, Ni2+) efficiently in ton-scale production is presented with the goal of mobile and stationary gas storage applications especially for hydrogen as future energy carrier. In addition, a new member of these series of materials, MOF-184-M (M = Mg2+, Ni2+) is introduced using ligand exchange strategy in order to produce a more porous analogue (possessing large aperture) without loss of crystallinity. This family comprising MOF-74/174/184 are characterized systematically for hydrogen adsorption properties by volumetric measurements with a Sieverts' apparatus. Replacing the linker by a longer one results in an increase of the BET area from 984 to 3154 m(2)/g and an enhancement of the excess cryogenic (77 K) hydrogen storage capacity from 1.8 to 4.7 wt%. The heat of adsorption of linker exchanged MOF-174/184 (as a function of uptake) shows similar values to the parent MOF-74, indicating successful construction of expanded MOFs in large scale production. Finally, a usable capacity of these MOFs is investigated for mobile application, revealing that the increasing surface area without strong binding metal sites through longer linker exchange is one of important parameters for improving usable capacity. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

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

Cryoadsorption on the inner surface of porous materials is a promising solution for safe, fast, and reversible hydrogen storage. Within the class of highly porous metal–organic frameworks, zeolitic imidazolate frameworks (ZIFs) show high thermal, chemical, and mechanical stability. In this study, we selected ZIF-8 synthesized mechanochemically by twin-screw extrusion as powder and pellets. The hydrogen storage capacity at 77 K and up to 100 bar has been analyzed in two laboratories applying three different measurement setups showing a high reproducibility. Pelletizing ZIF-8 increases the packing density close to the corresponding value for a single crystal without loss of porosity, resulting in an improved volumetric hydrogen storage capacity close to the upper limit for a single crystal. The high volumetric uptake combined with a low and constant heat of adsorption provides ca. 31 g of usable hydrogen per liter of pellet assuming a temperature–pressure swing adsorption process between 77 K – 100 bar and 117 K – 5 bar. Cycling experiments do not indicate any degradation in storage capacity. The excellent stability during preparation, handling, and operation of ZIF-8 pellets demonstrates its potential as a robust adsorbent material for technical application in pilot- and full-scale adsorption vessel prototypes

20 K H<sub>2</sub> Physisorption on Metal???Organic Frameworks with Enhanced Dormancy Compared to Liquid Hydrogen Storage

Liquid hydrogen (LH2) is the best way of transporting hydrogen, as its high volumetric energy density translates into a significant reduction in hydrogen transportation and refueling operations expenses. However, the phase transformation from liquid to gaseous hydrogen, due to heat leakage of the LH2 vessel, causes a considerable volume change, results in boil-off losses, and makes long-term storage/transportation problematic. These boil-off losses are a severe drawback for continental transportation through truck tube trailers having evaporative losses of about 3???15% per day (depending on the volume). Herein, hydrogen storage by cryo-adsorption using metal???organic frameworks (MOFs) is proposed as an alternative to reduce boil-off losses and enhance dormancy during continental transportation. The stronger van der Waals interaction operating between adsorbate and adsorbent leads to superdense H2 adsorption, which compensates for the space occupied by the adsorbent skeleton and results in a volumetric storage capacity comparable to that of LH2 tanks (???96%). Depending on the textural properties of MOFs, H2 desorption can start from 45 K, resulting in an extended dormancy time of the tank system. In addition, the observation of hindered rotational transition (J: 0 ??? 1) signal in neutron scattering analysis indicates that H2 are firmly attached and highly immobile on the adsorption sites. The hindered rotation by adsorption at 20 K on MOFs also suggests that the intermolecular separation is less than the bulk liquid (even solid) phase

An international laboratory comparison study of volumetric and gravimetric hydrogen adsorption measurements

In order to determine a material's hydrogen storage potential, capacity measurements must be robust, reproducible, and accurate. Commonly, research reports focus on the gravimetric capacity, and often times the volumetric capacity is not reported. Determining volumetric capacities is not as straight‐forward, especially for amorphous materials. This is the first study to compare measurement reproducibility across laboratories for excess and total volumetric hydrogen sorption capacities based on the packing volume. The use of consistent measurement protocols, common analysis, and figure of merits for reporting data in this study, enable the comparison of the results for two different materials. Importantly, the results show good agreement for excess gravimetric capacities amongst the laboratories. Irreproducibility for excess and total volumetric capacities is attributed to real differences in the measured packing volume of the material.JRC.C.1-Energy Storag