Nanostructured Hydrogen Storage Materials Research Articles

Mechanism and properties of emerging nanostructured hydrogen storage materials

AbstractHydrogen storage technology is one of the main challenges that restrict hydrogen utilization. Although there has been great progress in the research of hydrogen storage materials, seldom can they fulfill the criteria for onboard applications. Here, we focus on some innovative materials with complicated nanostructures and distinctive interactions with hydrogen, which may provide promising prospects. Recent advances in nano‐sized hydrides, catalytic adsorbents, multilayered materials, amorphous metal hydrides, and porous materials with open metal sites are discussed. We analyze the current problems of these hydrogen storage materials and provide suggestions for future development.

Micron-/nano-scale hierarchical structures and hydrogen storage mechanisms in a cast vanadium-based multicomponent alloy

Multicomponent vanadium-based alloys (MVAs), often considered as conventional coarse-grained alloys, have been extensively studied in past decades as important metal hydride electrodes and solid state hydrogen storage materials. A micron-scale microstructure composed of a V-based main phase and a TiNi-based secondary phase has been often used to explain the electrochemical performance of MVAs, where the micron-scale TiNi-based secondary phase with a three-dimensional network is considered as a catalyst for electrochemical reaction and/or a current collector. However, the atomic-scale microstructure of MVAs has been largely unknown to date. Here, using advanced aberration corrected electron microscopy, we have found micron-/nano-scale hierarchical structures in an as-cast MVA, V0.35Cr0.1Ti0.25Ni0.3. The micron-scale TiNi-phase contains VCr nanoprecipitates whereas the micron-scale VCr-phase contains TiNi nanoprecipitates and Ni-rich nanoclusters. In addition, we have found that the nanoprecipitates plays an essential role in the hydrogen storage, namely, TiNi nanoprecipitates with a diameter of approx. 30 nm absorb hydrogen faster than their VCr-matrix. Our studies revise conventional understanding on the microstructures in MVAs and the hydrogen storage mechanism, which may guide the development of nanostructured hydrogen storage materials for practical applications

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H2 absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.

Kinetics and Thermodynamics of Nanostructured Mg-Based Hydrogen Storage Materials Synthesized from Metal Nanoparticles

Mg, Ni, Co, Cu and Fe nanoparticles with a particle size of 30-300 nm were synthesized by hydrogen plasma metal reaction method. Nanostructured Mg-based hydrogen storage materials (Mg-H, Mg-Ni-H, Mg-Co-H, Mg-Cu-H and Mg-Fe-H systems) were synthesized from these metal nanoparticles. In this work, the kinetic and thermodynamic properties of these nanostructured hydrogen storage materials were studied. It was found that nanostructure could significantly enhance the hydrogen absorption kinetics but the thermodynamics (desorption enthalpy and entropy) does not change with downsizing in the size range of 50 to 300 nm.

A Solution Selection Model for Coaxial Electrospinning and Its Application to Nanostructured Hydrogen Storage Materials

Coaxial electrospinning was used to encapsulate the complex hydride ammonia borane in polystyrene to improve its properties as a hydrogen storage material. A solvent selection system was developed by using the Hansen solubility parameters to facilitate the choice of compatible solvents for core and shell. This enabled systematic optimization of the parameters needed for successful coelectrospinning. This approach has general application for any multiphase electrospinning system, including ones where the core is highly conducting or nonpolymeric. The resulting fiber morphologies depend strongly on the degree of miscibility of core and shell solutions. Fibers spun from immiscible core−shell solutions had a classic coaxial structure. Fibers produced from semimiscible core−shell solutions were highly porous, with inclusions extending through the fiber and an ordered radial and longitudinal distribution of nanoscale pores on the fiber surface. We suggest that this type of porosity may be due to an instability ...

ReleasingH2molecules with a partial pressure difference without the use of temperature

Using the pseudopotential density functional method as well as equilibrium thermodynamic functions, we explore the process of releasing H2 molecules adsorbed on a transition metal atom caused by the hydrogen-ammonia partial pressure difference. The H2 molecules bind to a transition metal atom at H2 pressure-NH3 pressure-temperature 50 atm-10-9 atm-25 {\deg}C, and they are released at 3 atm-10-6 atm-25 {\deg}C. This process involves the same mechanism responsible for carbon monoxide poisoning of hemoglobin with the O2-CO partial pressure difference. We show that our findings can be applicable to an approach to induce hydrogen desorption on nanostructured hydrogen storage materials without the need for increasing temperature.

Facile Preparation and Characterizations of Potential Low-Cost Nanostructured Materials for Hydrogen Storage

not Available.

Hydrogen-Induced Ostwald Ripening at Room Temperature in a Pd Nanocluster Film

The structural and morphological changes occurring in an ensemble of vapor deposited palladium nanoclusters have been studied after several hydrogenation cycles with x-ray diffraction, extended x-ray-absorption fine structure spectroscopy, Rutherford backscattering spectrometry, and STM. Initial hydrogenation increased the cluster size, a result that is attributed to hydrogen-induced Ostwald ripening. This phenomenon originates from the higher mobility of palladium atoms resulting from the low sublimation energy of the palladium hydride as compared to that of the palladium metal. The universality of this phenomenon makes it important for the application of future nanostructured hydrogen storage materials.

A theoretical study of activated nanostructured materials for hydrogen storage

The adsorption of molecular hydrogen on activated nanostruture materials is studied through computational simulations based on the pseudopotential density functional method. The hydrogen sorption energy and its diffusion through chemically activated pores in the materials are particularly investigated. It is found that the sorption energy of hydrogen reaches as high as about 29 kJ/mol at activated sites and can be controlled by modifying the structure and chemistry of the pores. The equilibrium pressure of hydrogen adsorption is also presented as a function of temperature by including the temperature and pressure dependence of hydrogen entropy. The desorption temperature is estimated to be close to 270 K for optimized activated nanostructures. This study demonstrates a pathway of materials search based on computational simulations for proper media that can hold hydrogen at ambient conditions through physisorption.

Combinatorial Search for Optimal Hydrogen-Storage Nanomaterials Based on Polymers

We perform an extensive combinatorial search for optimal nanostructured hydrogen-storage materials among various metal-decorated polymers using first-principles density-functional calculations. We take into account the zero-point vibration as well as the pressure- and temperature-dependent adsorption-desorption probability of hydrogen molecules. An optimal material we identify is Ti-decorated cis-polyacetylene with reversibly usable gravimetric and volumetric density of 7.6 wt % and 63 kg/m(3), respectively, near ambient conditions. We also propose "thermodynamically usable hydrogen capacity" as a criterion for comparing different storage materials.