Chemical Hydrogen Storage Materials Research Articles

Boosted Reactivity of Ammonia Borane Dehydrogenation over Ni/Ni2P Heterostructure

Ammonia borane (AB) is regarded as a highly promising candidate for chemical hydrogen-storage materials. Developing low-cost yet efficient catalysts for the dehydrogenation of AB is central to achieving hydrogen conversion. Here a heterostructure of Ni/Ni2P nanoparticles deposited on a defective carbon framework for the hydrolysis of AB is developed by elaborately controlling phosphorization conditions. The electronic structure and interfacial interaction of the ternary components are probed by synchrotron-based X-ray absorption fine structure and further simulated via density functional theory. By adjusting the content of Ni and Ni2P in the hetrostructure, the optimized hybrid exhibits catalytic performance of H2 generation from the hydrolysis of AB under ambient conditions with a turnover frequency of 68.3 mol (H2) mol-1 (Cat) min-1 and an activation energy ( Ea) of 44.99 kJ mol-1, implying its high potential as an efficient supplement for noble-metal-based catalysts in hydrogen energy applications.

The hydrolysis of ammonia borane catalyzed by NiCoP/OPC-300 nanocatalysts: high selectivity and efficiency, and mechanism

The development of highly efficient and cheap catalysts for the release of hydrogen from chemical hydrogen-storage materials is indispensable for the coming clean energy economy.

Discrepancy in the thermal decomposition/dehydrogenation of ammonia borane screened by thermogravimetric analysis

Ammonia borane NH3BH3 (AB), in pristine or destabilized state, has been much investigated as a solid-state chemical hydrogen storage material. The potential of such compound for thermolytic dehydrogenation (and decomposition) can be fast and reliably screened and assessed by thermogravimetric (TG) analysis via descriptors like both the onset temperature of dehydrogenation and the overall weight loss over the temperature range 100–200 °C. However, comparisons to results reported in the open literature need to be done with caution. The objective of the present article is thus to show that the thermolytic properties of AB determined by TG analysis are much dependent on the operation conditions. We have observed that much different results are obtained by changing the analyzer, and especially the crucible (comparable to a semi-closed reactor in one case or similar to an open reactor in the second case). For example, a stable AB sample is able to suffer a weight loss of 18.4 wt% starting from 116.5 °C when a semi-closed crucible is used, versus a weight loss of 51.9 wt% starting from 91 °C with the utilization of an open crucible. Our main results are reported herein in the form of a short technical communication: it aims at sharing our experimental observations in order to avoid misinterpretation and misunderstanding as for the TG analyses of AB and of any kind of derivatives. The present work should help in comparing the data available in the open literature with care and, from now on, should be regarded as a key study to report comparable TG results for AB thermolytic dehydrogenation.

Nanocrystalline metal organic framework (MIL-101) stabilized copper Nanoparticles: Highly efficient nanocatalyst for the hydrolytic dehydrogenation of methylamine borane

The copper nanoparticles stabilized by nanocrystalline MIL-101 framework (Cu/nano-MIL-101) was reproducibly prepared by following double solvent method combined with liquid phase chemical reduction technique. The characterization of the resulting new material was done by using various analytical techniques including ICP-OES, P-XRD, N2-adsorption-desorption, XPS, FE-SEM, SEM-EDX, BFTEM and HAADF-STEM; the summation of their results reveals that the formation of well-dispersed and very small sized (0.8 nm) copper nanoparticles within nanocrystalline MIL-101 framework. The catalytic performance of Cu/nano-MIL-101 in terms of activity and stability was tested in the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage. Cu/nano-MIL-101 catalyzes the hydrolytic dehydrogenation of methylamine borane with high activity (turnover frequency; TOF = 257 mol H2/mol Cu × h) and conversion (>99%) under air at room temperature. Moreover, these nano-MIL-101 framework stabilized copper nanoparticles show great durability against to sintering and leaching, which make Cu/nano-MIL-101 reusable nanocatalyst in the hydrolytic dehydrogenation of methylamine-borane. Cu/nano-MIL-101 nanocatalyst retains 83% of its inherent activity at complete conversion even at 10th recycle in the hydrolytic dehydrogenation of methylamine borane.

Atomic Layer Deposition of Ruthenium Nanoparticles on Electrospun Carbon Nanofibers: A Highly Efficient Nanocatalyst for the Hydrolytic Dehydrogenation of Methylamine Borane.

We report the fabrication of a novel and highly active nanocatalyst system comprising electrospun carbon nanofiber (CNF)-supported ruthenium nanoparticles (NPs) (Ru@CNF), which can reproducibly be prepared by the ozone-assisted atomic layer deposition (ALD) of Ru NPs on electrospun CNFs. Polyacrylonitrile (PAN) was electropsun into bead-free one-dimensional (1D) nanofibers by electrospinning. The electrospun PAN nanofibers were converted into well-defined 1D CNFs by a two-step carbonization process. We took advantage of an ozone-assisted ALD technique to uniformly decorate the CNF support by highly monodisperse Ru NPs of 3.4 ± 0.4 nm size. The Ru@CNF nanocatalyst system catalyzes the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage, with a record turnover frequency of 563 mol H2/mol Ru × min and an excellent conversion (>99%) under air at room temperature with the activation energy ( Ea) of 30.1 kJ/mol. Moreover, Ru@CNF demonstrated remarkable reusability performance and conserved 72% of its inherent catalytic activity even at the fifth recycle.

Facile synthesis of AuPd nanoparticles anchored on TiO2 nanosheets for efficient dehydrogenation of formic acid

Safe and efficient hydrogen storage is one of the key technologies for the widespread utilization of hydrogen energy. Formic acid (FA) is regarded as a safe and convenient chemical hydrogen storage material. However, the lack of highly efficient heterogeneous catalysts hinders its practical application. Herein, we presented a facile wet-impregnated deposition method to synthesize ultrafine AuPd alloy nanoparticles anchored on TiO2 nanosheets (AuPd/TiO2 nanosheets) which were used as high efficient catalysts for the dehydrogenation of FA. TiO2 nanosheets were calcined at different temperatures to modify the catalytic activity of catalyst. AuPd/TiO2 nanosheets-400 exhibits the superior activity for catalyzing the FA to release 96% of overall hydrogen content with an initial turnover frequency value of 592 mol H2 mol−1 metal h−1 at 25 °C and low activation energy of 11.8 kJ mol−1. Detailed characterizations show that the superior catalytic performance can be ascribed to the alloy structure of AuPd centers, the phase and crystallinity of TiO2 nanosheets, and the strong electron transfer interaction between AuPd nanoparticles and TiO2 nanosheets substrate.

Design tool for estimating chemical hydrogen storage system characteristics for light-duty fuel cell vehicles

The U.S. Department of Energy (DOE) developed a vehicle Framework model to simulate fuel cell-based light-duty vehicle operation for various hydrogen storage systems. This transient model simulates the performance of the storage system, fuel cell, and vehicle for comparison to Technical Targets established by DOE for four drive cycles/profiles. Chemical hydrogen storage models have been developed for the Framework for both exothermic and endothermic materials. Despite the utility of such models, they require that material researchers input system design specifications that cannot be estimated easily. To address this challenge, a design tool has been developed that allows researchers to directly enter kinetic and thermodynamic chemical hydrogen storage material properties into a simple sizing module that then estimates system parameters required to run the storage system model. Additionally, the design tool can be used as a standalone executable file to estimate the storage system mass and volume outside of the Framework model. These models will be explained and exercised with the representative hydrogen storage materials exothermic ammonia borane (NH3BH3) and endothermic alane (AlH3).

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

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.

Highly Dispersed Ultrafine Palladium Nanoparticles Enabled by Functionalized Porous Organic Polymer for Additive‐Free Dehydrogenation of Formic Acid

AbstractFormic acid (FA) is one of the most favorable chemical hydrogen storage materials for renewable energy transformation, the development of efficient heterogeneous catalysts for ultraclean H2 generation from FA in the absence of any alkalis or additives under mild conditions remains a major challenge. Here, we present a porous organic polymer containing triphenylamine (TPA) and 2,6‐bis(1,2,3‐triazol‐4‐yl)pyridyl (BTP) units (TB‐POP). The ultrafine palladium nanoparticles (NPs) with an average size of 1.5±0.6 nm can be facilely generated using convenient methods and are uniformly dispersed over the TB‐POP support. TPA and BTP units are homogeneously arranged in the host framework of TB‐POP; they serve as effective alternatives of basic sites to deprotonate FA into formate intermediates. Pd@TB‐POP has demonstrated remarkable catalytic activity and high selectivity in additive‐free dehydrogenation of aqueous FA solution. The value of initial turnover frequency (TOF) at 50 °C is as high as 1344 h−1. In sharp contrast, the use of sodium formate as an additive in the catalytic system results in the decrement of catalytic activity. The ultrafine palladium NPs are effectively immobilized during dehydrogenation of FA, and no aggregation of palladium NPs is observed after consecutive catalytic runs.

Electronic structure and chemical hydrogen storage of a porous sp3 tetragonal BC2N compound

By means of first-principles calculations, we predict an all-sp3 hybridized tetragonal BC2N compound (tet-BC2N) which is suggested to be obtained by transversely compressing (4,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) arrays. Accompanied by the transition from sp2-hybridized nanotubes to sp3-hybridized tet-BC2N, not only the bond length and diameter of tubes but also the electronic bandgap increases. Strikingly, the bandgap of the tet-BC2N can be mediated by controlling the ratio of BNNTs to total nanotubes from 1/2 to 1. However, it is almost a constant for the ratio changing from 0 to 1/2. In addition, this study shows that the tet-BC2N is a potential material for chemical hydrogen storage. While the weight percentage of hydrogen storage is up to 3.9 wt%, the adsorbed hydrogen still exists in the form of molecules. Even if the weight percentage of hydrogen storage increases to 7.6 wt%, the tet-BC2N is still intact but partial hydrogen molecules split into atoms.

Metal-Nanoparticle-Catalyzed Hydrogen Generation from Formic Acid.

To meet the ever-increasing energy demand, the development of effective, renewable, and environmentally friendly sources of alternative energy is imperative. Hydrogen (H2) is a renewable, clean energy carrier, which exhibits a threefold energy density compared to gasoline; H2 is considered one of the most promising alternative energy carriers for enabling a secure, clean energy future. However, the realization of a hydrogen economy is restricted by several unresolved issues. Particularly, one of the most difficult challenges is the development of a safe, efficient hydrogen storage and delivery system. To this end, hydrogen storage techniques based on liquid-phase chemical hydrogen storage materials have become an attractive choice. Formic acid (FA) with a high volumetric capacity of 53 g H2/L demonstrates promise as a safe, convenient liquid hydrogen carrier. However, generating H2 from FA in a controlled manner at ambient temperature is still challenging, which primarily depends on the catalyst used. Hence, for practical purposes, it is imperative to develop high-performance heterogeneous catalysts for the dehydrogenation of FA. Ultrasmall metal NPs with a high surface-to-volume ratio and "clean" surface, and hence a high density of active sites exposed to reactants, are of significance for heterogeneous catalysis. However, the size of these "clean" ultrasmall metal NPs inevitably increase, and these particles undergo aggregation during synthesis and catalysis because of their high surface energy. The immobilization of metal NPs into appropriate support materials affords considerable advantages for catalytic applications, which not only offers spatial confinement to control the nucleation and growth of particles, but also prevents them from aggregation; hence, catalytic performance is significantly enhanced. In addition, the functionalization of the support with electron-rich groups is beneficial to the formation of intermediates for FA dehydrogenation, which in turn promotes the catalytic performance. In this Account, studies of hydrogen generation from FA using heterogeneous catalysts were reviewed, mainly focusing on the results reported by our group. By varying support materials (metal-organic frameworks, silica, graphene, and porous carbons) and synthetic strategies, a wide range of highly active metal NP catalysts for efficient H2 generation from FA under mild conditions were developed. In addition, the design and synthetic strategies were described, by which the size and composition of the NPs, as well as the well-defined NPs-support interactions, can be controlled for the enhancement of catalytic performance for the FA dehydrogenation. Furthermore, the performance of the prepared catalysts for the effective release of H2 from FA for the purpose of liquid-phase chemical hydrogen storage was discussed. Finally, the challenges, expected improvements, and future opportunities in this research area were summarized.

Nitrogen-doped graphene hydrogel-supported NiPt-CeO x nanocomposites and their superior catalysis for hydrogen generation from hydrazine at room temperature

The safe and efficient storage and release of hydrogen is one of the key technological challenges for the fuel cell-based hydrogen economy. Hydrazine monohydrate has attracted considerable attention as a safe and convent chemical hydrogen-storage material. Herein, we report the facile synthesis of NiPt-CeO x nanocomposites supported by three-dimensional nitrogen-doped graphene hydrogels (NGHs) via a simple one-step co-reduction synthesis method. These catalysts were composition-dependent for hydrogen generation from an alkaline solution of hydrazine. (Ni5Pt5)1-(CeO x )0.3/NGH exhibited the highest catalytic activity, with 100% hydrogen selectivity and turnover frequencies of 408 h–1 at 298 K and 3,064 h–1 at 323 K. These superior catalytic performances are attributed to the electronic structure of the NiPt centers, which was modified by the electron interaction between NiPt and CeO x and the strong metal–support interaction between NiPt-CeO x and the NGH.

Enhanced catalytic activity of NiM (M = Cr, Mo, W) nanoparticles for hydrogen evolution from ammonia borane and hydrazine borane

In this work, a series of Ni1-xMx (M = Cr, Mo, W) nanoparticles (NPs) have been successfully synthesized via a simple surfactant-aided co-reduction method and employed as highly efficient and cost effective catalysts for hydrogen generation from aqueous solution of ammonia borane (NH3BH3, AB) at room temperature. It is found that the as-synthesized NiM NPs (M = Cr, Mo, W) exhibit much higher catalytic performance for the hydrolysis of AB as compared to that of pure Ni NPs. In addition, among all the Ni1-xMx (M = Cr, Mo, W) NPs, the Ni0.9Cr0.1, Ni0.9Mo0.1, and Ni0.8W0.2 NPs show the highest catalytic activities with the turnover frequency (TOF) values of 10.7, 27.3 and 25.0 mol H2 (mol metal min)−1, respectively. Remarkably, these optimized NiM catalysts can also perform efficiently in the hydrolysis of hydrazine borane (N2H4BH3, HB). The present low-cost and high-performance of the NiM catalysts system may encourage the practical application of AB and HB as the promising chemical hydrogen storage materials.

Dehydrogenation of Ammonia Borane by Metal Nanoparticle Catalysts

Ammonia borane (AB), having a high hydrogen density of 19.6 wt %, has attracted much attention as a promising chemical hydrogen storage material. In the past few years, a number of highly active metal nanoparticle (NP) catalysts, which are easy to handle and separate, have been developed for AB dehydrogenation. In this Perspective, we summarize new progress in the development of metal NP catalysts, which are categorized into monometallic and heterometallic catalysts, with excellent activity and high recyclability for different AB dehydrogenation pathways, including solvolysis (hydrolysis and methanolysis) in protic solvents and dehydrocoupling in nonprotic solvents, and we survey the corresponding methods for the regeneration of AB. Moreover, the merits and drawbacks of solvolysis and dehydrocoupling are discussed.

Mechanistic insights of metal acetylacetonate-aided dehydrocoupling of liquid-state ammonia borane NH3BH3

Ammonia borane NH3BH3 solubilized in organic solvent is a potential liquid-state chemical hydrogen storage material. In this study, metal acetylacetonates like Fe(O2C5H7)3, Co(O2C5H7)2, Ni(O2C5H7)2, Pd(O2C5H7)2, Pt(O2C5H7)2 and Ru(O2C5H7)3 are considered for assisting dehydrocoupling of ammonia borane in diglyme (0.135 M) at 50oC. The molar ratio between ammonia borane and metal acetylacetonate is fixed at 100. A protocol for the separation of the soluble and insoluble fractions present in the slurry is proposed; it consists in using acetonitrile to make the precipitation of metal-based compounds easier and to solubilize boron-based intermediates/products. The nature of the metal does not affect the dehydrocoupling mechanisms, the 11B{1H} NMR spectra showing the formation of the same reaction intermediates. The aforementioned metal acetylacetonates do mainly have effect on the kinetics of dehydrocoupling. Dehydrocoupling takes place heterogeneously and dehydrogenation of ammonia borane in these conditions leads to the formation of polyborazylene via intermediates like e.g., B-(cyclodiborazanyl) amine-borane and borazine. Our main results are reported and discussed herein.

High Pressure Behavior of Hydrogen Storage Material Guanidinium Borohydride

A combination of synchrotron powder angle-dispersive X-ray diffraction (ADXRD) and Raman spectroscopy has been utilized to study high pressure behavior of the chemical hydrogen storage material guanidinium borohydride (GBH) [C(NH2)3]+[BH4]−. A reversible structural phase transition was observed at approximately 0.4 GPa, evidenced by the obvious changes in ADXRD patterns and Raman spectra. Both Raman spectra and the first-principles calculation revealed that new dihydrogen bonds generated under high pressure, which was proposed to be the reason for the observed phase transition. This research explored the pressure induced changes of GBH and studied the evolution of dihydrogen bonds, which can give insight into the improvement of the hydrogen release properties.

Catalytic decomposition of carbon-based liquid-phase chemical hydrogen storage materials for hydrogen generation under mild conditions

The increasing demand of energy requires the development of sufficient and sustainable energy sources. However, the upcoming hydrogen economy is suffering from challenges which need to be solved. In this context, the search for liquid hydrogen storage materials and successful utilisation is crucial due to the high gravimetric and volumetric hydrogen densities, easy recharging, low capital investment, and low potential risks. In this review, we survey the progress made in hydrogen generation from carbon-based liquid-phase chemical hydrogen storage materials, focusing mainly on the catalytic decomposition of formic acid for hydrogen production.

Coupling of exothermic and endothermic hydrogen storage materials

Chemical hydrogen storage (CHS) materials are a high-storage-density alternative to the gaseous compressed hydrogen currently used to provide hydrogen for fuel cell vehicles. One of the challenges of CHS materials is addressing the energy barriers required to break the chemical bonds and release the hydrogen. Coupling CHS reactions that are endothermic and exothermic during dehydrogenation can improve onboard energy efficiency and thermal control for the system, making such materials viable. Acceptable coupling between reactions requires both thermodynamic and kinetic considerations. In this work, models were developed to predict the reaction enthalpy and rate required to achieve high conversions for both reactions based on experimental measurements. Modeling results show that the coupling efficiency of exothermic and endothermic reactions is more sensitive to the ratio of the exothermic and endothermic enthalpies than to the ratio of the rates of the two steps. Modeling results also show that a slower endothermic step rate is desirable to permit sufficient heating of the reactor by the exothermic step. We look at two examples of a sequential and parallel reaction scheme and provide some of the first published insight into the required temperature range to maximize the hydrogen release from 1,2-BN cyclohexane and indoline.

In Pursuit of Sustainable Hydrogen Storage with Boron-Nitride Fullerene as the Storage Medium.

Using well calibrated DFT studies we predict that experimentally synthesized B24 N24 fullerene can serve as a potential reversible chemical hydrogen storage material with hydrogen-gas storage capacity up to 5.13 wt %. Our theoretical studies show that hydrogenation and dehydrogenation of the fullerene framework can be achieved at reasonable rates using existing metal-free hydrogenating agents and base metal-containing dehydrogenation catalysts.

Fe-Ni 2元系ナノ粒子担持CeO2触媒を用いた化学的水素貯蔵材料からの高効率水素生成

Fe-Ni 2元系ナノ粒子担持CeO2触媒を用いた化学的水素貯蔵材料からの高効率水素生成