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Nanocomposites of sulfur encapsulated in single-walled carbon nanotubes show increased hydrogen density in pores through enhanced electrostatic potential.

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.

Introducing heterostructure to graphitic carbon nitrides (g-C3N4) can improve the activity of visible-light-driven catalysts for efficient treatment of multiple toxic pollutants in water. Here we report for the first time that a complex material can be constructed from an oxygen-doped g-C3N4 and MIL-53(Fe) metal-organic framework using a facile hydrothermal synthesis and recycled polyethylene terephthalate from plastic waste. The novel multi-walled nanotube structure of the O-g-C3N4/MIL-53(Fe) composite which enables unique interfacial charge transfer at the heterojunction showed an obvious enhancement in separation efficiency of the photochemical electron-hole pairs. This resulted in narrow bandgap energy (2.30 eV compared to 2.55 eV in O-g-C3N4), high photocurrent intensity (0.17 mA cm-2 compared to 0.12 mA cm-2 and 0.09 mA cm-2 in MIL-53(Fe) and O-g-C3N4, respectively), and excellent catalytic performance in the photodegradation of anionic azo dyes (95% RR 195 and 99% RY 145 degraded after 4 h, and only a minor change in the efficiency observed after four consecutive tests). These results demonstrate the development of new catalysts made from waste feedstocks that show high stability, ease of fabrication and can operate in natural light for environmental remediation.

The hydrations of the excipients stable α-lactose (Lαs), with two particle sizes, and trehalose have been studied by neutron powder diffraction; analysis of the Avrami plots, derived from the bulk polycrystalline phase compositions, allows elucidation of the kinetics and mechanisms involved in these hydration processes.