Showing papers on "Hydrogen storage published in 2018"

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols.

Abstract: Hydrogen gas is a storable form of chemical energy that could complement intermittent renewable energy conversion. One of the main disadvantages of hydrogen gas arises from its low density, and therefore, efficient handling and storage methods are key factors that need to be addressed to realize a hydrogen-based economy. Storage systems based on liquids, in particular, formic acid and alcohols, are highly attractive hydrogen carriers as they can be made from CO2 or other renewable materials, they can be used in stationary power storage units such as hydrogen filling stations, and they can be used directly as transportation fuels. However, to bring about a paradigm change in our energy infrastructure, efficient catalytic processes that release the hydrogen from these molecules, as well as catalysts that regenerate these molecules from CO2 and hydrogen, are required. In this review, we describe the considerable progress that has been made in homogeneous catalysis for these critical reactions, namely, the hy...

Nanostructured Metal Hydrides for Hydrogen Storage.

Abstract: Knowledge and foundational understanding of phenomena associated with the behavior of materials at the nanoscale is one of the key scientific challenges toward a sustainable energy future. Size reduction from bulk to the nanoscale leads to a variety of exciting and anomalous phenomena due to enhanced surface-to-volume ratio, reduced transport length, and tunable nanointerfaces. Nanostructured metal hydrides are an important class of materials with significant potential for energy storage applications. Hydrogen storage in nanoscale metal hydrides has been recognized as a potentially transformative technology, and the field is now growing steadily due to the ability to tune the material properties more independently and drastically compared to those of their bulk counterparts. The numerous advantages of nanostructured metal hydrides compared to bulk include improved reversibility, altered heats of hydrogen absorption/desorption, nanointerfacial reaction pathways with faster rates, and new surface states cap...

Local generation of hydrogen for enhanced photothermal therapy.

Abstract: By delivering the concept of clean hydrogen energy and green catalysis to the biomedical field, engineering of hydrogen-generating nanomaterials for treatment of major diseases holds great promise. Leveraging virtue of versatile abilities of Pd hydride nanomaterials in high/stable hydrogen storage, self-catalytic hydrogenation, near-infrared (NIR) light absorption and photothermal conversion, here we utilize the cubic PdH0.2 nanocrystals for tumour-targeted and photoacoustic imaging (PAI)-guided hydrogenothermal therapy of cancer. The synthesized PdH0.2 nanocrystals have exhibited high intratumoural accumulation capability, clear NIR-controlled hydrogen release behaviours, NIR-enhanced self-catalysis bio-reductivity, high NIR-photothermal effect and PAI performance. With these unique properties of PdH0.2 nanocrystals, synergetic hydrogenothermal therapy with limited systematic toxicity has been achieved by tumour-targeted delivery and PAI-guided NIR-controlled release of bio-reductive hydrogen as well as generation of heat. This hydrogenothermal approach has presented a cancer-selective strategy for synergistic cancer treatment.

Enabling Effective Electrocatalytic N2 Conversion to NH3 by the TiO2 Nanosheets Array under Ambient Conditions

Abstract: NH3 serves as an attractive hydrogen storage medium and a renewable energy sector for a sustainable future. Electrochemical reduction is a feasible ambient reaction to convert N2 to NH3, while it needs efficient electrocatalysts for the N2 reduction reaction (NRR) to meet the challenge associated with N2 activation. In this Letter, we report on our recent experimental finding that the TiO2 nanosheets array on the Ti plate (TiO2/Ti) is effective for electrochemical N2 conversion to NH3 at ambient conditions. When tested in 0.1 M Na2SO4, such TiO2/Ti attains a high NH3 yield of 9.16 × 10-11 mol s-1·cm-2 with corresponding Faradaic efficiency of 2.50% at -0.7 V vs reversible hydrogen electrode, outperforming most reported aqueous-based NRR electrocatalysts. It also shows excellent selectivity for NH3 formation with high electrochemical stability. The superior NRR activity is due to the enhanced adsorption and activation of N2 by oxygen vacancies in situ generated during electrochemical tests.

Surface Engineering of a Supported PdAg Catalyst for Hydrogenation of CO2 to Formic Acid: Elucidating the Active Pd Atoms in Alloy Nanoparticles

Abstract: The hydrogenation of carbon dioxide (CO2) to formic acid (FA; HCOOH), a renewable hydrogen storage material, is a promising means of realizing an economical CO2-mediated hydrogen energy cycle. The development of reliable heterogeneous catalysts is an urgent yet challenging task associated with such systems, although precise catalytic site design protocols are still lacking. In the present study, we demonstrate that PdAg alloy nanoparticles (NPs) supported on TiO2 promote the efficient selective hydrogenation of CO2 to give FA even under mild reaction conditions (2.0 MPa, 100 °C). Specimens made using surface engineering with atomic precision reveal a strong correlation between increased catalytic activity and decreased electron density of active Pd atoms resulting from a synergistic effect of alloying with Ag atoms. The isolated and electronically promoted surface-exposed Pd atoms in Pd@Ag alloy NPs exhibit a maximum turnover number of 14 839 based on the quantity of surface Pd atoms, which represents a m...

Record High Hydrogen Storage Capacity in the Metal–Organic Framework Ni2(m-dobdc) at Near-Ambient Temperatures

Abstract: Hydrogen holds promise as a clean alternative automobile fuel, but its on-board storage presents significant challenges due to the low temperatures and/or high pressures required to achieve a sufficient energy density. The opportunity to significantly reduce the required pressure for high density H2 storage persists for metal–organic frameworks due to their modular structures and large internal surface areas. The measurement of H2 adsorption in such materials under conditions most relevant to on-board storage is crucial to understanding how these materials would perform in actual applications, although such data have to date been lacking. In the present work, the metal–organic frameworks M2(m-dobdc) (M = Co, Ni; m-dobdc4– = 4,6-dioxido-1,3-benzenedicarboxylate) and the isomeric frameworks M2(dobdc) (M = Co, Ni; dobdc4– = 1,4-dioxido-1,3-benzenedicarboxylate), which are known to have open metal cation sites that strongly interact with H2, were evaluated for their usable volumetric H2 storage capacities ove...

High-Purity Hydrogen Generation via Dehydrogenation of Organic Carriers: A Review on the Catalytic Process

Abstract: High-purity hydrogen delivery for stationary and mobile applications using fuel cells is a subject of rapidly growing interest. As a consequence, the development of efficient storage technologies and processes for hydrogen supply is of primary importance. Promising hydrogen storage techniques rely on the reversibility and high selectivity of liquid organic hydrogen carriers (LOHCs), for example, methylcyclohexane, decalin, dibenzyltoluene, or dodecahydrocabazole. LOCHs have high gravimetric and volumetric hydrogen density, and they involve low risk and capital investment because they are largely compatible with the current transport infrastructure used for fossil fuels. A further advantage comes from the high purity (close to 100%) of the hydrogen generated by dehydrogenation, suitable to directly feed fuel cells without the need for bulky purification modules. Partial dehydrogenation (PDH) of liquid fuels has recently emerged as a transition technology for hydrogen delivery purposes. The principle is to ...

Methanol Production and Applications: An Overview

Abstract: Methanol, or methyl alcohol, is the simplest alcohol, appearing as a colorless liquid with a distinctive smell. Nowadays, it is considered one of the most useful chemical compounds. In fact, it is one of the most promising building blocks for obtaining more complex chemical structures, such as acetic acid, methyl tertiary butyl ether, dimethyl ether, methylamine, etc. Furthermore, methanol is also considered a promising clean-burning fuel with a high octane number. Knowing that CO2 and H2 are among the precursors in methanol synthesis, it is noteworthy that the conversion of CO2 to methanol can be considered a promising method for significantly reducing CO2 emissions, and that methanol production can also be used as a convenient energy carrier for hydrogen storage and conservation. In fact, methanol synthesis is the second source, after ammonia production, of hydrogen consumption (which has the highest energy content per weight) via several reactions, such as partial oxidation, steam reforming, autothermal reforming, methanol decomposition, or methanol-water solution electrolysis. Finally, among the recent attractive applications of methanol, the most promising for the future are the production of DME, the production of hydrogen, and the direct methanol fuel cell (DMFC). This chapter is an overview of not only common feedstocks used in the production processes for obtaining methanol (natural gases, CO2, or char/biomass), but also of the historical production processes (such as the BASF process, also known as the “high-pressure method,” and the ICI process, also known as the “low-pressure method”) and the most innovative trends for industrial applications.

Facile synthesis of graphene-supported Ni-CeO x nanocomposites as highly efficient catalysts for hydrolytic dehydrogenation of ammonia borane

Abstract: Development of low-cost and high-performance catalysts for hydrogen generation via hydrolysis of ammonia borane (NH3BH3, AB) is a highly desirable pathway for future hydrogen utilization. In this work, Ni nanocatalysts doped with CeOx and supported on graphene (Ni-CeOx/graphene) were synthesized via a facile chemical reduction route and applied as robust catalysts for the hydrolysis of AB in aqueous solution at room temperature. The as-synthesized Ni-CeOx/graphene nanocomposites (NCs) exhibited excellent catalytic activity with a turnover frequency (TOF) as high as 68.2 min−1, which is 49-fold higher than that for a simple Ni nanoparticle catalyst and is among the highest values reported for non-noble metal catalysts in AB hydrolysis. The development of efficient and low-cost Ni-CeOx/graphene catalysts enhances the feasibility of using ammonia borane as a chemical hydrogen storage material, which may find application ina hydrogen fuel-cell based economy.

Hydrogen spillover through Matryoshka-type (ZIFs@) n−1 ZIFs nanocubes

Abstract: Hydrogen spillover phenomenon is well-documented in hydrogenation catalysis but still highly disputed in hydrogen storage Until now, the existence of hydrogen spillover through metal–organic frameworks (MOFs) remains a topic of ongoing debate and how far the split hydrogen atoms diffuse in such materials is unknown Herein we provide experimental evidence of the occurrence of hydrogen spillover in microporous MOFs at elevated temperatures, and the penetration depths of atomic hydrogen were measured quantitatively We have made Matryoshka-type (ZIFs@)n−1ZIFs (where ZIFs = ZIF-8 or ZIF-67) nanocubes, together with Pt nanoparticles loaded on their external surfaces to produce atomic hydrogen Within the (ZIFs@)n−1ZIFs, the ZIF-8 shell served as a ruler to measure the travelling distance of H atoms while the ZIF-67 core as a terminator of H atoms In addition to the hydrogenolysis at normal pressure, CO2 hydrogenation can also trace the migration of H atoms over the ZIF-8 at high pressure Hydrogen spillover is well-documented in hydrogenation catalysis, but its existence through metalorganic frameworks (MOFs) remains controversial Here, the authors provide evidence of the occurrence of hydrogen spillover in microporous MOFs at elevated temperatures, and measure quantitatively the penetration depths of atomic hydrogen

Recent strategies targeting efficient hydrogen production from chemical hydrogen storage materials over carbon-supported catalysts

Abstract: There is an evident urgent need to find a renewable and clean energy vector to ensure the worldwide energy supply while minimizing environmental impacts, and hydrogen stands out as a promising alternative energy carrier. The social concern around its safe storage is constantly fostering the search for alternative options to conventional storage methods and, in this context, chemical hydrogen storage materials have produced abundant investigations with particular attention to the design of heterogeneous catalysts that can boost the generation of molecular hydrogen. Among the chemical hydrogen storage materials, formic acid and ammonia–borane hold tremendous promise, and some of the recent strategies considered for the preparation of high-performance carbon-supported catalysts are summarized in this review. The outstanding features of carbon materials and their versatility combined with the tunability of the metal active phase properties (e.g., morphology, composition, and electronic features) provide numerous options for the design of promising catalysts. Precise control over the size and composition of metal nanoparticles is critical to the safe production of hydrogen from chemical storage systems. Kohsuke Mori and Hiromi Yamashita from Osaka University in Japan and colleagues review recent progress in producing hydrogen gas for fuel cell technology from the energy-rich molecules formic acid and ammonia borane. By immobilizing nanosized metal catalysts onto carbon-based supports with shapes including ultrasmall spheres, nanotubes, and graphene oxide sheets, researchers can tune hydrogen generation rates to record-high levels while still ensuring easy recovery and reuse. Catalytic reactions with formic acid can be improved by using noble metal-based palladium catalysts. While ruthenium nanocatalysts are favored for ammonia borane reactions, less expensive metal nickel and cobalt nanoparticles are gaining attention. This review recapitulates some of the most representative studies recently reported on carbon-supported catalysts for the hydrogen production from formic acid and ammonia borane by considering both active phase features and support properties. Several synthetic strategies are herein summarized to highlight the versatility of carbon materials in affording highly-performing catalysts for the hydrogen production from hydrogen carrier molecules.

Structure and Hydrogenation Properties of a HfNbTiVZr High-Entropy Alloy.

Abstract: A high-entropy alloy (HEA) of HfNbTiVZr was synthesized using an arc furnace followed by ball milling The hydrogen absorption mechanism was studied by in situ X-ray diffraction at different temperatures and by in situ and ex situ neutron diffraction experiments The body centered cubic (BCC) metal phase undergoes a phase transformation to a body centered tetragonal (BCT) hydride phase with hydrogen occupying both tetrahedral and octahedral interstitial sites in the structure Hydrogen cycling of the alloy at 500 °C is stable The large lattice strain in the HEA seems favorable for absorption in both octahedral and tetrahedral sites HEAs therefore have potential as hydrogen storage materials because of favorable absorption in all interstitial sites within the structure

Vanadium oxide nanoparticles supported on cubic carbon nanoboxes as highly active catalyst precursors for hydrogen storage in MgH2

Abstract: Magnesium hydride (MgH2) has attracted intense interest as a high-capacity hydrogen storage material. However, high thermal stability and slow kinetics limit its practical applications. Herein, vanadium oxide nanoparticles supported on cubic carbon nanoboxes (nano-V2O3@C) are synthesized successfully by using MIL-47(V) as a precursor, and superior catalytic effects derived from the nano-V2O3@C composite towards the hydrogen storage reaction of MgH2 are demonstrated. The MgH2-9 wt% nano-V2O3@C sample starts releasing hydrogen at 215 °C, which is 60 °C lower than that of the additive-free MgH2. At 275 °C, approximately 6.4 wt% of hydrogen is released from the MgH2-9 wt% V2O3@C sample within 20 min. The dehydrogenated sample absorbs hydrogen even at room temperature under 50 bar of hydrogen pressure, and rehydrogenation is complete within 700 s at 150 °C. XRD and XPS measurements identify the existence of metallic V after ball milling, and its presence remains nearly constant in the subsequent dehydrogenation/hydrogenation process upon heating. Further ab initio calculations reveal that the presence of V facilitates the breaking of the Mg–H bond of the MgH2 unit, which is reasonably responsible for the significantly reduced operating temperatures and improved kinetics of the V-catalysed MgH2.

Effect of Li2CoMn3O8 Nanostructures Synthesized by a Combustion Method on Montmorillonite K10 as a Potential Hydrogen Storage Material

Abstract: This paper outlines new design nanocomposites (Li2CoMn3O8/K10) for electrochemical hydrogen storage with an emphasis on the optimal conditions to achieve higher performance. Li2CoMn3O8/K10 nanocomposites were fabricated by loading different ratios of the Li2CoMn3O8 (5%, 10%, and 20%) inside the montmorillonite K10. Electrochemical properties of the samples montmorillonite K10, Li2CoMn3O8, and the respective nanocomposites were studied by chronopotentiometry charge–discharge techniques in alkaline medium. The Li2CoMn3O8 nanostructures were synthesized by a facile combustion method in the presence of various carboxylic acids as fuel and capping agents. The influence of carboxylic acids on the size, morphology, and homogeneity of the samples was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Fourier transform infrared (FT-IR) were applied to investigate the purity and chemical compositions of the samples. ...