Including Hydrogen Storage Research Articles

A first-principles prediction of an sp3 carbon allotrope comprising four-, five-, six-, and eight-member rings

A superhard carbon phase with Pmmm (D2h1, 47) symmetry is predicted by using a recently developed particle swarm optimization method for searching for crystal structures. The carbon phase is an orthorhombic crystal system that contains 16 atoms per unit cell, named oC16, which has an all-sp3-hybridized bonding network and contains a large cavity. oC16 has a distinct topology, including zigzag four-, five-, six-, and eightfold carbon rings. The dynamic, elastic, and electronic properties of oC16 are investigated by first-principles calculations, and the results show that oC16 is more energetically stable than the experimentally synthesized T-carbon, BC8, and BC12. The phonon spectra and elastic constants confirm its dynamical and mechanical stability at zero pressure, respectively. The calculated bulk moduli and hardness indicate that oC16 is an ultra-incompressible and superhard material. Analyzing its electronic band structure reveals that oC16 has insulation characteristics with an indirect bandgap of 4.42 eV. Also investigated is how the elastic moduli of the oC16 phase depend on the crystal orientation. Because of its superhard and porous properties, the potential uses of oC16 include hydrogen storage, molecular sieves, coating, and tools for cutting, polishing, and grinding.

Fluorine Substitution in Magnesium Hydride as a Tool for Thermodynamic Control

Metal hydrides continue to vie for attention as materials in multiple technological applications including hydrogen storage media, thermal energy storage (TES) materials, and hydrogen compressors. ...

Large plasmonic field enhancement on hydrogen-absorbing transition metals at lower frequencies: Implications for hydrogen storage, sensing, and nuclear fusion

The plasmonic enhancement of electromagnetic field energy density around planar surfaces of hydrogen-absorbing transition metals, Pd, Ti, and Ni, has been quantitatively investigated, to explore the use of plasmonics in the forthcoming hydrogen economy. We have observed that a large degree of energy focusing, with the enhancement factor over several hundreds, is available for these transition metals in the microwave region, even surpassing the enhancement for noble metals. This finding could potentially lead to technological progress in various hydrogen-related energy applications including hydrogen storage, sensing, and nuclear fusion.

Producing High Concentrations of Hydrogen in Palladium via Electrochemical Insertion from Aqueous and Solid Electrolytes

Metal hydrides are critical materials in numerous technologies including hydrogen storage, gas separation, and electrocatalysis. Here, using Pd–H as a model metal hydride, we perform studies of ele...

Novel RGO-ZnWO<sub>4</sub>-Fe<sub>3</sub>O<sub>4</sub> Electrodes Material for Energy Storage Device Applications

As the global concerns in the development of human civilization, the scientific and technological issues of energy utilization and environment protection are currently facing challenges. Nowadays, enormous energy demands of the world are mainly met by the non-renewable and environmental unfriendly fossil fuels. To replace the conventional energy platform, a pursuit of renewable and clean energy sources and carriers, including hydrogen storage, lithium batteries, and supercapacitors. Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. Herein, we report novel RGO-ZnWO₄-Fe₃O₄ electrodes material can be synthesized using one step microwave irradiation technique and reported as an electrode material for supercapacitors applications. The surface morphology, chemical composition and electronic structure of the RGO-ZnWO₄-Fe₃O₄ electrodes were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performance of the RGO-ZnWO₄-Fe₃O₄ electrodes has been investigated using cyclic voltammetry (CV) techniques. The result reveals that a specific capacitance of 480 F/g, an energy density of 15 Wh/kg and power density of 1719.5 W/kg is observed over RGO-ZnWO₄-Fe₃O₄ electrodes materials. The cost effective electrodes materials of RGO-ZnWO₄-Fe₃O₄ can be useful for future electrochemical energy storage device applications.

Total Cost of Ownership of Fuel Cell Electric Vehicles Using Expert Assessments

We calculated the total cost of ownership (TCO) of fuel cell electric vehicles (FCEVs) in 2017, 2020, 2035, and 2050. Our TCO model incorporates proton exchange membrane fuel cell (PEMFC) cost and durability data that we obtained during our expert elicitation interviews [1]. Our assumptions, including hydrogen storage system and fuel costs, are consistent with those published by the U.S. Department of Energy [2, 3]. We characterized the uncertainty associated with FCEV life cycle costs, and we compared our FCEV projections to the DOE’s 2035 projections for internal combustion engine vehicles (ICEVs), battery electric vehicles (BEVs), hybrid-electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). In our sensitivity analyses, we studied the dependence of FCEV TCO on vehicle lifetime, hydrogen fuel cost, and hydrogen storage system cost. All monetary values are expressed in 2017 USD. On median, we estimated the FCEV TCO to be $0.42/mile in 2017, $0.33/mile in 2020, $0.19/mile in 2035, and $0.18/mile in 2050 (Figure 1). Our 2017 and 2020 estimates ranged widely. Our 2017 estimates ranged from $0.40 to $0.75/mile and 2020 estimates ranged from $0.31 to $0.51/mile. By 2035, FCEVs could be competitive with ICEVs, BEVs, HEVs, and PHEVs, as long as the PEMFC stack lasts sufficiently long. If the FCEV’s lifetime falls below 11 yrs, FCEVs could become more expensive than competing vehicles. At about 11 yrs, the FCEV’s TCO exceeds that of the BEV. If stack durability remains a challenge, replacing the stack could be economical. Achieving a hydrogen fuel cost below $4/kg H2 and hydrogen system cost below $390/kg H2 could further improve FCEVs’ competitiveness.

Functionalization of Metal Surfaces Using Hydride Intermediates

Noble metals have important applications in an array of fields including hydrogen storage and sensing, chemical catalysis, and fuel cells. They offer high volumetric power density in metal hydride batteries and pseudocapacitors. However, the kinetics of chemical reactions at their surfaces are often limited by the high stability of surface-bound species. Theoretical[1] and experimental[2],[3] reports suggest that adlayers of other metals can destabilize the surface species, which should increase chemical reaction rates. We have developed a room-temperature electroless atomic layer deposition (ALD) technique in which we grow adlayers of other metals on palladium and platinum substrates.[4] The method contrasts with electrochemical ALD,[3] which requires applying a current to a substrate, and to gas-phase ALD, which requires elevated temperatures that can damage some substrates. Exposing a substrate to dilute hydrogen/nitrogen gas mixtures causes a surface hydride to form. Subsequent addition of a solution containing noble metal salts displaces the surface hydride with the reduced metal in a surface-limited reaction. This process can be repeated, and the thickness of the surface coverage increases, as shown by X-ray photoelectron spectroscopy. We have developed variations of the method that allow a nanoporous layer to be grown in a stepwise manner, and that use aqueous reducing agents to form the hydride instead of hydrogen gas. This technique requires no specialized equipment, and makes use of benign reagents. It is surface-limited in nature, but is not limited to an electrode. This confers important advantages of high scalability and compatibility with complex surface topologies; conductive substrates are not required. We believe that this versatile technique could be widely applied by synthetic chemists to take advantage of enhanced catalytic properties of near-surface alloys. This work was supported by the Laboratory-Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. SAND2018-3092 A [1] Greeley, J.; Mavrikakis, M. J. Phys. Chem. B 2005, 109, 3460−3471. [2] Bartlett, P. N.; Marwan, J. Phys. Chem. Chem. Phys.2004, 6, 2895−2898. [3] Sheridan, L. B.; Yates, V. M.; Benson, D. M.; Stickney, J. L.; Robinson, D. B. Electrochim. Acta 2014, 128, 400−405. [4] Cappillino, P. J.; Sugar, J. D.; El Gabaly, F.; Cai, T. Y.; Liu, Z.; Stickney, J. L.; Robinson, D. B. Langmuir 2014, 30, 4820−4829.

Gaseous sorption and electrochemical properties of rare-earth hydrogen storage alloys and their representative applications: A review of recent progress

The improvement of hydrogen storage materials is a key issue for storage and delivery of hydrogen energy before its potential can be realized. As hydrogen storage media, rare-earth hydrogen storage materials have been systematically studied in order to improve storage capacity, kinetics, thermodynamics and electrochemical performance. In this review, we focus on recent research progress of gaseous sorption and electrochemical hydrogen storage properties of rare-earth alloys and highlight their commercial applications including hydrogen storage tanks and nickel metal hydride batteries. Furthermore, development trend and prospective of rare-earth hydrogen storage materials are discussed.

A Critical Review of Mg-Based Hydrogen Storage Materials Processed by Equal Channel Angular Pressing

As a kind of cost-efficient hydrogen storage materials with high hydrogen capacity and light weight, Mg-based alloys have attracted much attention. This review introduces an effective technique in producing bulk ultrafine-grained (UFG) Mg alloys and promoting its hydrogen storage property, namely, equal-channel angular pressing (ECAP). This paper briefly describes the technical principle of ECAP and reviews the research progress on hydrogen storage properties of ECAP-processed Mg alloys. Special attention is given to their hydrogen storage behaviors including hydrogen storage dynamics, capacity, and cycling stability. Finally, it analyzes the factors that affect the hydrogen storage properties of ECAP-processed Mg alloys, such as the grain sizes, lattice defects, catalysts, and textures introduced by ECAP process.

Alkali metal silanides α-MSiH3: A family of complex hydrides for solid-state hydrogen storage

The alkali metal silanides α-MSiH3 appear to be a promising family of complex hydrides for solid-state hydrogen storage. Herein the structural, energetic and electronic properties of α-MSiH3 silanides (M = Li, Na, K, Rb, Cs) and MSi Zintl phases are systematically investigated for the first time by using first-principles calculations method based on density functional theory. The structural parameters of α-MSiH3 and MSi including lattice constants and atomic positions are determined through geometry optimization. The obtained results are close to the experimental data analysed from X-ray and neutron powder diffraction. The calculations of formation enthalpy show that α-KSiH3, α-RbSiH3 and α-CsSiH3 silanides are easier to be synthetized relative to α-LiSiH3 and α-NaSiH3, which interprets well the lower thermostabilities of experimental α-LiSiH3 and α-NaSiH3. Nevertheless, LiSi, KSi and CsSi phases are easier to be formed relative to NaSi and RbSi. The calculations of hydrogen desorption enthalpy reveal that the dehydrogenation abilities of α-MSiH3 silanides along the decomposition path of α-MSiH3→MSi + H2 are gradually enhanced in the order of α-CsSiH3, α-RbSiH3, α-KSiH3, α-NaSiH3 and α-LiSiH3, which may be originated from their decreasing thermostabilities. From a comprehensive point of view including hydrogen storage capacity, thermostability and dehydrogenation ability, α-KSiH3 (∼4.29 wt%) is identified as the most promising alkali metal silanide for reversible hydrogen storage. Analysis of electronic structures indicates that a significant charge transfer leads to positively charged M ions and negatively charged SiH3 complex, which constitutes the ionic bonding between them. The bonding within SiH3 complex not only involves the covalent hybridization between Si (3s) (3p) and H (1s) orbitals, but also exhibits some ionic bond characteristics due to the partial charge transfer from Si to H. The covalent bonding interactions between H and Si atoms within SiH3 mainly dominate the thermostabilities and dehydrogenation properties of α-MSiH3 silanides.

High and low activation energy kinetics are different: Implications for hydrogen and protons in condensed matter

ABSTRACTAt high activation energy, kinetic processes require the accumulation of several excitations in order to take place. This accumulation implies an entropy, which we call multi-excitation entropy. This explains the isokinetic rule, which itself explains the existence of isoequilibrium relations. Understanding the implications of these effects helps clarify the microscopic mechanisms in kinetic processes, including hydrogen storage, and transport of protons, and potentially, of other ions, in condensed matter.

High-Throughput Screening of Metal–Organic Frameworks for Hydrogen Storage at Cryogenic Temperature

Metal–organic frameworks (MOFs) have attracted significant interest as a class of adsorbent materials for gas storage applications, including hydrogen storage for fuel cell vehicles. Here, we evaluated 137 953 hypothetical MOFs for hydrogen storage at cryogenic conditions (77 K) by determining the deliverable storage capacity between 100 and 2 bar, using grand canonical Monte Carlo simulations. The highest predicted volumetric capacity for a structure in this study is 50 g/L, and the highest gravimetric capacity is almost 25 wt %. We find that the optimal void fraction is 0.9 and the optimal pore diameter is 12–15 A. MOFs with larger pores have significant regions in the center of the pore with low hydrogen density, which lowers the storage efficiency. We give examples of MOFs with very large pores in which the hydrogen capacity can potentially be increased using catenation or functional groups to reduce the pore size and increase the surface area per volume. We also introduce a screening parameter, the b...

Polyacrylonitrile nanofibers with added zeolitic imidazolate frameworks (ZIF-7) to enhance mechanical and thermal stability

Zeolitic imidazolate framework 7/polyacrylonitrile (ZIF-7/PAN) nanofiber mat of high porosity and surface area can be used as a flexible fibrous filtration membrane that is subjected to various modes of mechanical loading resulting in stresses and strains. Therefore, the stress-strain relation of ZIF-7/PAN nanofiber mats in the elastic and plastic regimes of deformation is of significant importance for numerous practical applications, including hydrogen storage, carbon dioxide capture, and molecular sensing. Here, we demonstrated the fabrication of ZIF-7/PAN nanofiber mats via electrospinning and report their mechanical properties measured in tensile tests covering the elastic and plastic domains. The effect of the mat fabrication temperature on the mechanical properties is elucidated. We showed the superior mechanical strength and thermal stability of the compound ZIF-7/PAN nanofiber mats in comparison with that of pure PAN nanofiber mats. Material characterization including scanning electron microscope, energy-dispersive X-ray spectroscopy, tensile tests, differential scanning calorimetry, and Fourier transform infrared spectroscopy revealed the enhanced chemical bonds of the ZIF-7/PAN complex.

(Invited) Diagnostics of Microstructure and Properties of Polymer Electrolyte Fuel Cell Catalyst Layer

Rising levels of greenhouse gas emissions, especially carbon dioxide (CO2), are regarded as one of the causes of global warming in recent years. To develop technologies for reducing CO2emission plays an important role for vehicle manufacturers, and Nissan has been developing zero-emission vehicles (ZEVs) such as battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs). The biggest issues to penetrate FCEVs into the market are cost reduction of polymer electrolyte fuel cell (PEFC) power system including hydrogen storage subsystem, and development of hydrogen infrastructure. Related to the former issue, one of the most significant challenges is to reduce platinum group metals (PGM) in fuel cell stacks. PGM are used as electrocatalyst and contained in catalyst layers (CLs) of membrane electrode assemblies (MEAs) in the stack. Various kinds of research activities on PEFC electrocatalyst have been reported so far, indicating high oxygen reduction reaction (ORR) activity and durability mainly measured in aqueous electrolyte systems such as a rotating disk electrode method.1-8 On the other hand, electrocatalyst is mixed with electrolyte to form CLs through deposition and solidification process. From industrial point of view, it is needed that performance of the electrocatalyst should be guaranteed as CL in MEA. CL is a multi-scale component, i.e. micro-scale porous electrode consisting of nano-scale materials (Fig. 1), where electrochemical reaction and mass transport occur simultaneously. Micro and nano structure of CL has been revealed gradually by means of characterization techniques remarkably progressed recently, such as electron microscope. 9-10However, it is still under development to characterize and diagnose structure and properties of CLs as overall and average value. To reduce PGM usage, so far Nissan has been doing research and development on CL based on the strategy to understand the correlation between CL/MEA performance and the consisting materials through properties and structure via key mechanism.11-20In this presentation, diagnostics of PEFC CLs related to activity and mass transport are explained, mainly focusing on the unique analysis Nissan has been developing thus far.

Kinetic Stability of MOF-5 in Humid Environments: Impact of Powder Densification, Humidity Level, and Exposure Time.

Metal-organic frameworks (MOFs) are an emerging class of microporous, crystalline materials with potential applications in the capture, storage, and separation of gases. Of the many known MOFs, MOF-5 has attracted considerable attention because of its ability to store gaseous fuels at low pressure with high densities. Nevertheless, MOF-5 and several other MOFs exhibit limited stability upon exposure to reactive species such as water. The present study quantifies the impact of humid air exposure on the properties of MOF-5 as a function of exposure time, humidity level, and morphology (i.e., powders vs pellets). Properties examined include hydrogen storage capacity, surface area, and crystallinity. Water adsorption/desorption isotherms are measured using a gravimetric technique; the first uptake exhibits a type V isotherm with a sudden increase in uptake at ∼50% relative humidity. For humidity levels below this threshold only minor degradation is observed for exposure times up to several hours, suggesting that MOF-5 is more stable than generally assumed under moderately humid conditions. In contrast, irreversible degradation occurs in a matter of minutes for exposures above the 50% threshold. Fourier transform infrared spectroscopy indicates that molecular and/or dissociated water is inserted into the skeletal framework after long exposure times. Densification into pellets can slow the degradation of MOF-5 significantly, and may present a pathway to enhance the stability of some MOFs.

Van der Waals force: a dominant factor for reactivity of graphene.

Reactivity control of graphene is an important issue because chemical functionalization can modulate graphene's unique mechanical, optical, and electronic properties. Using systematic optical studies, we demonstrate that van der Waals interaction is the dominant factor for the chemical reactivity of graphene on two-dimensional (2D) heterostructures. A significant enhancement in the chemical stability of graphene is achieved by replacing the common SiO2 substrate with 2D crystals such as an additional graphene layer, WS2, MoS2, or h-BN. Our theoretical and experimental results show that its origin is a strong van der Waals interaction between the graphene layer and the 2D substrate. This results in a high resistive force on graphene toward geometric lattice deformation. We also demonstrate that the chemical reactivity of graphene can be controlled by the relative lattice orientation with respect to the substrates and thus can be used for a wide range of applications including hydrogen storage.

ChemInform Abstract: Recent Advances in the Design Strategies for Porphyrin‐based Coordination Polymers

AbstractReview: 89 refs.

Atomic-Layer Electroless Deposition on Noble Metal Powders

Palladium has important applications in an array of fields including hydrogen storage and sensing, chemical catalysis and fuel cells. It offers high volumetric power density in metal hydride batteries and pseudocapacitors. However, the rates of hydride formation and hydrogen release in such applications are often limited by the high stability of the surface hydride formed on Pd. Theoretical and experimental reports suggest that adlayers of metals that form weaker surface Pd-H interactions can destabilize the surface hydride, which should facilitate hydrogen transport.We have developed a room-temperature electroless atomic layer deposition (ALD) technique in which we grow such layers on palladium powder. This is in contrast to electrochemical ALD, which requires applying a current to a substrate, and to gas-phase ALD, which requires elevated temperatures that can damage some substrates. Exposing a suspension of powder to dilute hydrogen/nitrogen gas mixtures causes a surface hydride to form. Subsequent addition of a solution containing noble metal salts displaces the surface hydride with the reduced metal in a surface-limited reaction. This process can be repeated, and the thickness of the surface coverage increases, as shown by X-ray photoelectron spectroscopy.This technique requires no specialized equipment, and makes use of benign reagents. It is surface-limited in nature, but is not limited to an electrode. This confers important advantages of high scalability and compatibility with complex surface topologies; conductive substrates are not required. We believe that this versatile technique could be widely applied by synthetic chemists to take advantage of enhanced catalytic properties of near-surface alloys.In addition to details on the preparation and characterization of Pd powder with adlayers of other noble metals, we will show evidence of enhanced hydrogen transport in these samples. A kinetic model for this process that includes gas flow, solid-state hydrogen diffusion and surface hydride formation will be presented.Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-8925A

Integration of large-scale hydrogen storages in a low-carbon electricity generation system

This study investigates the overall feasibility of large energy storages with hydrogen as energy carrier onsite with a pre-combustion carbon capture and storage coal gasification plant and assesses the general impacts of such a backup installation on an electricity generation system with high wind power portion. The developed system plant configuration consists of four main units namely the gasification unit, main power unit, backup power unit including hydrogen storage and ancillary power unit. Findings show that integrating a backup storage in solid or gaseous hydrogen storage configuration allows to store excessive energy under high renewable power output or low demand and to make use of the stored energy to compensate low renewable output or high power demand. The study concludes that the developed system configuration reaches much higher load factors and efficiency levels than a plant configuration without backup storage, which simply increases its power unit capacity to meet the electricity demand. Also from an economical point of view, the suggested system configurations are capable to achieve lower electricity generation costs.

Removal of Heavy Metals from Wastewater Using Carbon Nanotubes

The discovery of carbon nanotubes (CNTs) and the prospect of developing novel carbon-based nanomaterials have attracted researchers worldwide. CNTs have great potential as a novel type of adsorbent due to their unique properties such as chemical stability, mechanical and thermal stability, and the high surface area, which leads to various applications including hydrogen storage, protein purification and water treatment. Removal of heavy metals from industrial wastewater leads to the biggest challenge nowadays. To reduce environmental problems, the CNTs are promising candidates for the adsorption of heavy metals. In this study, extremely brief summaries of liquid pollutant purification are reviewed.