Direct Evidence for Solid-like Hydrogen in a Nanoporous Carbon Hydrogen Storage Material at Supercritical Temperatures

Abstract

Here we report direct physical evidence that confinement of molecular hydrogen (H2) in an optimized nanoporous carbon results in accumulation of hydrogen with characteristics commensurate with solid H2 at temperatures up to 67 K above the liquid-vapor critical temperature of bulk H2. This extreme densification is attributed to confinement of H2 molecules in the optimally sized micropores, and occurs at pressures as low as 0.02 MPa. The quantities of contained, solid-like H2 increased with pressure and were directly evaluated using in situ inelastic neutron scattering and confirmed by analysis of gas sorption isotherms. The demonstration of the existence of solid-like H2 challenges the existing assumption that supercritical hydrogen confined in nanopores has an upper limit of liquid H2 density. Thus, this insight offers opportunities for the development of more accurate models for the evaluation and design of nanoporous materials for high capacity adsorptive hydrogen storage.

The usable capacity of porous materials for hydrogen storage

“…Usually, the density of the adsorbed phase is identified with the liquid density at ambient pressure (0.07 g/ml); however, some measurements indicate a slightly lower [3] or even higher value [4,5].…”

Diamond-Like Carbon Nanofoam from Low-Temperature Hydrothermal Carbonization of a Sucrose/Naphthalene Precursor Solution

“…Also, catalytic properties of the foam [79], as well as gas- [80] and glucose-sensing properties [81] or photoluminescence [82] are related to a graphitic or graphene-like interior of the foams. In particular, hydrogen storage, long proposed for graphitic carbon materials [83], has recently been considered for nanoporous carbons [84][85][86]. We note that a strong sp 3 contribution, as observed for the nanofoam in this work, will affect the general properties of these foams as well as their possible use in future technologies.…”

Quantum confinement of molecular deuterium clusters in carbon nanotubes: ab initio evidence for hexagonal close packing

“…There exists direct experimental evidence for solid-like packing of hydrogen at supercritical temperatures. 6 Moreover, recent low-temperature (11-22 K) neutron-diffraction-based experimental measurements by Cabrillo et al have provided evidence for the formation of a crystalline hcp structure of molecular deuterium clusters inside carbon nanotubes (CNTs). 7,8 This work has raised the fundamental question of the role of nuclear quantum effects for hydrogen adsorption and confinement at low temperatures.…”