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)

http://www-personal.umich.edu/~djsiege/Energy_Storage_Lab/Publications_files/CSR_H2_storage.pdf

High capacity hydrogen storage materials: attributes for automotive applications and techniques for materials discovery

Iron oxide surfaces

There is great interest in iron oxides, especially in nanosized form, for both fundamental and practical reasons. Because of its polymorphism, iron(III) oxide (ferric oxide, Fe2O3) is one of the most interesting and potentially useful phases of the iron oxides. Each of the four different known crystalline Fe2O3 polymorphs (alpha-, beta-, gamma-, and epsilon-Fe2O3) has unique biochemical, magnetic, catalytic, and other properties that make it suitable for specific technical and biomedical applications. High temperature treatment is a key step in most syntheses of iron(III) oxides but often triggers polymorphous transformations that result in the formation of undesired mixtures of Fe2O3 polymorphs. It is therefore important to control the parameters that induce polymorphous transformations when seeking to prepare a given Fe2O3 polymorph as a single phase; identifying and understanding these parameters is a major challenge in the study of the polymorphism of solid compounds. This review discusses the depende...

Polymorphous Transformations of Nanometric Iron(III) Oxide: A Review

Nanocatalysts are characterised by the unique nanoscale properties that originate from their highly reduced dimensions. Extensive studies over the past few decades have demonstrated that the size and shape of a catalyst particle on the nanometre scale profoundly affect its reaction performance. In particular, controlling the catalyst particle morphology allows a selective exposure of a larger fraction of the reactive facets on which the active sites can be enriched and tuned. This desirable surface coordination of catalytically active atoms or domains substantially improves catalytic activity, selectivity, and stability. This phenomenon is called morphology-dependent nanocatalysts: catalyst particles with anisotropic morphologies on the nanometre scale greatly affect the reaction performance by selectively exposing the desired facets. In this review, we highlight important progress in morphology-dependent nanocatalysts based on the use of rod-shaped metal oxides with characteristic redox and acid-base features. The correlation between the catalytic properties and the exposed facets verifies the chemical nature of the morphology effect. Moreover, we provide an overview of the interactions between the rod-shaped oxides and the metal nanoparticles in metal-oxide catalyst systems, involving crystal-facet-selective deposition of metal particles onto different crystal facets in the oxide supports. A fundamental understanding of active sites in morphologically tuneable oxides enclosed by the desired reactive facets is expected to direct the development of highly efficient nanocatalysts.

Morphology-dependent nanocatalysts: Rod-shaped oxides

The prerequisite for widespread use of hydrogen as an energy carrier is the development of new materials that can safely store it at high gravimetric and volumetric densities. Metal borohydrides M(BH4)n (n is the valence of metal M), in particular, have high hydrogen density, and are therefore regarded as one such potential hydrogen storage material. For fuel cell vehicles, the goal for on-board storage systems is to achieve reversible store at high density but moderate temperature and hydrogen pressure. To this end, a large amount of effort has been devoted to improvements in their thermodynamic and kinetic aspects. This review provides an overview of recent research activity on various M(BH4)n, with a focus on the fundamental dehydrogenation and rehydrogenation properties and on providing guidance for material design in terms of tailoring thermodynamics and promoting kinetics for hydrogen storage.

/pdf/recent-progress-in-metal-borohydrides-for-hydrogen-storage-2r304dem34.pdf

Lene Mosegaard

Papers

Hydrogen sorption properties of MgH2-LiBH4 composites

Formation of γ-Fe2O3 nanoparticles and vacancy ordering: An in situ X-ray powder diffraction study

Intermediate phases observed during decomposition of LiBH4