Manipulation of the crystalline phase diagram of hydrogen through nanoscale confinement effects in porous carbons

Lui R Terry*, Stephane Rols, Mi Tian, Ivan Da Silva, Simon J Bending, V. P. Ting*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

4 Citations (Scopus)
39 Downloads (Pure)

Abstract

Condensed phases of molecular hydrogen (H2) are highly desired for clean energy applications ranging from hydrogen storage to nuclear fusion and superconductive energy storage. However, in bulk hydrogen, such dense phases typically only form at exceedingly low temperatures or extremely high (typically hundreds of GPa) pressures. Here, confinement of H2 within nanoporous materials is shown to significantly manipulate the hydrogen phase diagram leading to preferential stabilization of unusual crystalline H2 phases. Using pressure and temperature-dependent neutron scattering at pressures between 200–2000 bar (0.02–0.2 GPa) and temperatures between 10–77 K to map out the phase diagram of H2 when confined inside both meso- and microporous carbons, we conclusively demonstrate the preferential stabilisation of face-centred cubic (FCC) solid ortho-H2 in microporous carbons, at temperatures five times higher than would be possible in bulk H2. Through examination of nanoconfined H2 rotational dynamics, preferential adsorption and spin trapping of ortho-H2, as well as the loss of rotational energy and severe restriction of rotational degrees of freedom caused by the unique micropore environments, are shown to result in changes to phase behaviour. This work provides a general strategy for further manipulation of the H2 phase diagram via nanoconfinement effects, and for tuning of anisotropic potential through control of confining material composition and pore size. This approach could potentially provide lower energy routes to the formation and study of more exotic non-equilibrium condensed phases of hydrogen that could be useful for a wide range of energy applications.
Original languageEnglish
Pages (from-to)7250-7261
Number of pages12
JournalNanoscale
Volume14
Issue number19
Early online date6 May 2022
DOIs
Publication statusPublished - 6 May 2022

Bibliographical note

Funding Information:
The authors thank the US Army Research Office for funding this project (W911NF-19-1-0321-P00001) and the UK Engineering and Physical Sciences Research Council (EPSRC) for an EPSRC Research Fellowship for VPT (EP/R01650X/1). The authors thank the Science and Technology Facilities Council (STFC) for funding and allocation of ISIS beamtime (Proposal number RB1910448) and the Institut Laue Langevin for beamtime (Proposal number IN4C 7-05-468). Thanks also goes to Prof Steve Tennison and Tom Avery (MAST Carbon International) for providing the TE7 carbon beads and Volker Presser (INM, University of Saarbruken, Germany) for providing the OLC carbons, and to Rafael Balderas Xicohtencatl and Anibal J. Ramirez-Cuesta (Oak Ridge National Laboratories) for useful discussions. VPT designed and managed the project and obtained the funding. LT and MT performed the materials characterization and testing. LT, VPT, and MT carried out the neutron experiments with the support of IdS, SR and SB. LT led the data analysis, with all authors contributing to data interpretation and the drafting of the manuscript.

Publisher Copyright:
© 2022 The Royal Society of Chemistry

Keywords

  • hydrogen
  • H2
  • Phase behavior
  • Neutron diffraction
  • neutron scattering
  • Condensed Matter & Materials Physics
  • nanoconfinement
  • porous carbon
  • Porous materials

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