Widespread adoption of hydrogen as a vehicular fuel depends critically upon the ability to store hydrogen on-board at high volumetric and gravimetric densities, as well as on the ability to extract/insert it at sufficiently rapid rates. As current storage methods based on physical means-high-pressure gas or (cryogenic) liquefaction-are unlikely to satisfy targets for performance and cost, a global research effort focusing on the development of chemical means for storing hydrogen in condensed phases has recently emerged. At present, no known material exhibits a combination of properties that would enable high-volume automotive applications. Thus new materials with improved performance, or new approaches to the synthesis and/or processing of existing materials, are highly desirable. In this critical review we provide a practical introduction to the field of hydrogen storage materials research, with an emphasis on (i) the properties necessary for a viable storage material, (ii) the computational and experimental techniques commonly employed in determining these attributes, and (iii) the classes of materials being pursued as candidate storage compounds. Starting from the general requirements of a fuel cell vehicle, we summarize how these requirements translate into desired characteristics for the hydrogen storage material. Key amongst these are: (a) high gravimetric and volumetric hydrogen density, (b) thermodynamics that allow for reversible hydrogen uptake/release under near-ambient conditions, and (c) fast reaction kinetics. To further illustrate these attributes, the four major classes of candidate storage materials-conventional metal hydrides, chemical hydrides, complex hydrides, and sorbent systems-are introduced and their respective performance and prospects for improvement in each of these areas is discussed. Finally, we review the most valuable experimental and computational techniques for determining these attributes, highlighting how an approach that couples computational modeling with experiments can significantly accelerate the discovery of novel storage materials (155 references).

Filling the pores: A zinc‐based metal–organic framework (MOF) can be transformed reversibly from an open (a) to a dense (b) configuration. The microporous solid is the first example of a MOF that is highly selective in the gas‐chromatographic separation of alkanes.

Epitaxial attachment of quantum dots into ordered superlattices enables the synthesis of quasi-two-dimensional materials that theoretically exhibit features such as Dirac cones and topological states, and have major potential for unprecedented optoelectronic devices. Initial studies found that disorder in these structures causes localization of electrons within a few lattice constants, and highlight the critical need for precise structural characterization and systematic assessment of the effects of disorder on transport. Here we fabricated superlattices with the quantum dots registered to within a single atomic bond length (limited by the polydispersity of the quantum dot building blocks), but missing a fraction (20%) of the epitaxial connections. Calculations of the electronic structure including the measured disorder account for the electron localization inferred from transport measurements. The calculations also show that improvement of the epitaxial connections will lead to completely delocalized electrons and may enable the observation of the remarkable properties predicted for these materials.

Sleeping disorder is a major health threatening in high-pace modern society. Characterizing sleep behavior with pressure-sensitive, simple fabrication, and decent washability still remains a challenge and highly desired. Here, a pressure-sensitive, large-scale, and washable smart textile is reported based on triboelectric nanogenerator (TENG) array as bedsheet for real-time and self-powered sleep behavior monitoring. Fabricated by conductive fibers and elastomeric materials with a wave structure, the TENG units exhibit desirable features including high sensitivity, fast response time, durability, and water resistance, and are interconnected together, forming a pressure sensor array. Furthermore, highly integrated data acquisition, processing, and wireless transmission system is established and equipped with the sensor array to realize real-time sleep behavior monitoring and sleep quality evaluation. Moreover, the smart textile can further serve as a self-powered warning system in the case of an aged nonhospitalized patients falling down from the bed, which will immediately inform the medical staff. This work not only paves a new way for real-time noninvasive sleep monitoring, but also presents a new perspective for the practical applications of remote clinical medical service.

We experimentally investigate several hydrogen storage reactions based on thermodynamic destabilization of LiBH4. The destabilized mixtures include nine M(H2)−LiBH4 compositions, where M(H2) = Al, Mg, Ti, Sc, V, Cr, MgH2, CaH2, or TiH2, which were selected on the basis of favorable thermodynamics predicted by recent first-principles computational study (Siegel, D. J.; Wolverton, C.; Ozoliņš, V. Phys. Rev. B: Condens. Matter, Mater. Phys. 2007, 76, 134102). For all compositions, our measurements reveal significant kinetic barriers for hydrogen release, evidenced by high desorption temperatures (>300 °C) and exceedingly slow hydrogen release rates. Characterization of the desorbed reaction phases indicate that less than half of the mixtures examined (M(H2) = MgH2, Mg, Al, and CaH2) follow the thermodynamically expected reaction pathway, resulting in the formation of metal boride products (MgB2, AlB2, and CaB6, respectively). Hydrogen release/uptake data for these compositions indicate that the MgH2−(LiBH4)2 and Al−(LiBH4)2 reactions are reversible (10.2 and 6.7 wt %, respectively) at increased desorption pressures of 5 and 3 bar H2, respectively, while CaH2−(LiBH4)6 is irreversible under the conditions tested. For the remaining compositions, M(H2) = Sc, V, Cr, Ti, and TiH2, we surmise that substantial limitations in kinetics inhibit the expected formation of metal boride products. Finally, we discuss how the relative physical properties, in particular the melting point of the reactants and products, correlate with desorption route and reversibility.