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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.

Current state-of-the-art methods consist of containing high-pressure compressed hydrogen in composite cylinders, with solid-state hydrogen storage materials an alternative that could improve on storage performance by enhancing volumetric densities. A new strategy that uses cryogenic temperatures to load hydrogen (cryocharging) is proposed and analysed in this work, comparing densities and final storage pressures for empty cylinders and containers with the high-surface area materials MIL-101 (Cr) and AX-21. Results show cryocharging as a viable option, as it can substantially lower the charging (at 77 K) and final pressures (at 298 K) for the majority of the cases considered. Kinetics are an equally important requirement for hydrogen storage systems, so the effective diffusivities at these conditions for both materials were calculated, and showed values comparable to the ones estimated in metal–organic frameworks and zeolites from quasielastic neutron scattering and molecular simulations. High-surface area materials tailored for hydrogen storage are a promising route for storage in mobile applications and results show that cryocharging is a promising strategy for hydrogen storage systems, since it increases volumetric densities and avoids energy penalties of operating at high pressures and/or low temperatures. Keywords: Hydrogen storage, Nanoporous materials, Hydrogen storage systems, Adsorption

Experimental results for methane adsorption on two high-surface area carbons (TE7-20 and AX-21) and one metal-organic framework (MIL-101(Cr)) are presented, with isotherms obtained at temperatures ranging from 250 to 350 K and at pressures up to 15 MPa. The isotherms were analysed to determine if these materials could be viable alternatives for on-board solid-state storage of methane. The results show a very high adsorbate density in the pores of all materials, which for some can even exceed liquid methane density. At moderate pressures below 5 MPa, the calculated total energy densities are close to the energy density of methanol, and are almost 40% of the energy density of gasoline (petrol). Compared with standard compression at the same conditions, the results show that adsorption can be a competitive storage alternative, as it can offer equal volumetric capacities at much lower pressures, hence reducing the energy penalty associated with compression. It is shown that the optimal conditions for adsorptive methane storage in these materials are at moderate pressure ranges, where the gains in amounts stored when using an adsorbent are more pronounced when compared to cylinders of compressed methane gas at the same operating conditions. Finally, a study on deliverable capacities for adsorbed methane was carried out, simulating two charging pressure scenarios of 3.5 and 6.5 MPa and discharge at 0.5 MPa. The results show that some of the tested materials have high working volumetric capacities, with some materials displaying more than 140 kg m(-3) volumetric working capacity for charging at 6.5 MPa and delivery at 0.5 MPa. (C) 2015 Elsevier B.V. All rights reserved.

Microbial lipids offer a promising feedstock for renewable biofuels. However, one of the major concerns with their conversion from lipids into suitable fuels is the high sterol content of the lipid. This is especially problematic for lipids obtained from oleaginous yeasts, as there are some indications that the sterol content could inhibit catalyst performance during hydrotreating. In this investigation a sterol-rich model feedstock (a 50:50 mixture of cholesterol and rapeseed oil, “RC50”) and an unrefined microbial lipid derived from the oleaginous yeast Metschkownia pulcherrima were converted to a diesel-like fuel in a single step via catalytic cracking. Far from reducing catalyst performance the cracking of the sterol groups liberated hydrogen, resulting in a reduction in the olefin content as well as an increase in the aromatic content of the fuel. The cracking of RC50 over Pd/C resulted in a fuel with a comparable product distribution to ultra-low sulphur diesel (ULSD), with high levels of linear alkanes and approximately 10 wt% aromatics. Cracking of unrefined yeast lipid over Pd/C was shown to result in an energy dense, hydrocarbon fuel suitable for marine applications (unblended) or a road transport fuel at 50% v/v blends with ULSD.

There is much current interest in the storage of hydrogen in porous materials for mobile energy applications. Despite significant hydrogen storage capacities having been observed recently for some synthesised materials, the identification of optimal operating conditions (pressure and temperature) is perhaps an even more important consideration from an engineering and applied science perspective. There will be pressure and temperature limits for effective use of an adsorptive storage system, because the adsorbent will always displace a volume in the storage container, and so at very high pressures the amount of hydrogen stored at a given temperature will be greater for a container with no adsorbent. In order for an adsorbent to be used there has to be some gain in the amount of the hydrogen stored to compensate for the cost and mass of the solid. We present a methodology by which the pressure and temperature ranges where it is advantageous to use adsorptive storage can be easily identified and the real gain of using such systems in terms of the absolute amount of hydrogen stored can be quantified. Using a well-characterised commercial activated carbon as an example system, we modelled high pressure hydrogen sorption isotherms and identified the operating conditions for which there is a significant increase in storage capacity from using an adsorbent as opposed to storage in the same volume via compression of hydrogen at the same temperature. A novel comparison of the density enhancement in the micropores with respect to the bulk hydrogen gas, as well as the influence of incorporating different amounts of adsorbent into a high pressure storage container is also presented.

We present results of investigations into improving methods by which gas sorption data are collected and reported. The focus is the accurate comparison of hydrogen storage capacities of different nanoporous materials. The aim is to produce a more rigorous approach to the assessment of the hydrogen storage capacities of different nanoporous materials through formulation of meticulous and systematic data collection routines for production of universally reproducible H2 isotherms over a wide range of pressure and temperature conditions. Effects of a range of experimental variables are examined and recommendations for the optimisation of data collection routines are given.

The binary pnictide ‘SnSb’ has been re-investigated using a combination of X-ray, synchrotron and electron diffraction as well as electron microprobe analysis. Its structure was found to be incommensurately modulated with an underlying rhombohedral parent structure of space group symmetry R 3 ¯ m (No. 166), unit cell parameters a h = b h = 4.3251 ( 4 ) A , c h = 5.3376 ( 6 ) A in the hexagonal setting. The incommensurate primary modulation wave vector q h = 1 . 3109 ( 9 ) c h * and the superspace group symmetry is R 3 ¯ m (0, 0, ∼1.311) (No. 166.1). The refinement of the incommensurate structure indicates that the satellite reflections arise from displacive shifts of presumably essentially pure Sn and Sb layers along the hexagonal c-axis, with increasing distance between the Sn-layers and decreasing distance between the Sb layers.

A careful investigation has been carried out into the space group symmetries, structures and crystal chemistries of the 1:2 B-site ordered triple perovskites A3Co2+Nb5+2O9 (A=Ca2+, Sr2+, Ba2+) using a combination of bond valence sum calculations, powder XRD and electron diffraction. A recent investigation of these compounds by Yin et al. reported a random distribution of Co2+ and Nb5+ ions onto the perovskite B-site positions and hence Pm 3 m (a=ap, subscript p for parent perovskite sub-structure) space group symmetry for the A=Ba and Sr compounds and a monoclinically distorted variant thereof (although no space group was given) in the case of the A=Ca compound. An electron diffraction study, however, shows that the A=Ba compound occurs in a 1:2 B site ordered trigonal P 3 m1 , a h = b p − c p , b h = c p − a p , c h = a p + b p + c p structure type while both the A=Ca and Sr compounds occur at room temperature in monoclinic P121/c1, a m =[ 1 1 2] p , b m =[1 1 0] p , c m =3[110] p , perovskite-related structure types. The latter monclinic structure type can be described as a modulated variant of the 1:2 B site ordered trigonal P 3 m1 structure type with the additional modulations associated with a b–b−c+ octahedral tilt sequence. Bond valence sum calculations are used to explain why this should be so as well as to provide a useful zeroth-order approximation to the structures of each of the compounds.

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.