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Dihydrogen Hδ+⋅⋅⋅Hδ− bonding that is accepted as an important unconventional hydrogen bonding could play a key role in molecular self-assembly of amine boranes. It is with this goal in mind that we have studied the behavior of n-dodecylamine borane nC12H25NH2BH3 (C12AB) dissolved in anhydrous THF. C12AB can be easily synthesized with a purity higher than 99% by Lewis acid-base reaction of a BH3 complex with n-dodecylamine nC12H25NH2. It is stable when dissolved in THF that is a good solvent of it. However, it is unstable in the presence of moisture, readily hydrolyzing and producing water-soluble borates. Molecular self-assembly of C12AB has thus to be studied in anhydrous conditions, which allows observing by DLS and SAXS-WAXS the formation of core-shell aggregates in anhydrous THF. The aggregates consist of about five self-assembling stretched C12AB molecules where the NH2BH3 groups are in the core of 3 A and the alkyl chains in an outer-shell.

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.

High-pressure X-ray diffraction and Raman spectroscopy in a diamond anvil cell were used to study the insertion of the chemical hydrogen storage material, ammonia borane, in the one-dimensional pores of the zeolite theta-1 TON. Heating of this material up to 300 °C under pressures up to 5 GPa resulted in the release of a significant amount of hydrogen due to the conversion of ammonia borane confined in the channels of TON and outside the zeolite to polyaminoborane and then polyiminoborane chains. The filling of TON with hydrogen resulted in a much greater increase in unit cell volume than that corresponding to thermal expansion of normal compact inorganic solids. This process at high temperature is accompanied by a phase transition from the collapsed high-pressure Pbn21 form to the more symmetric Cmc21 phase with expanded pores. This material has a high capacity for hydrogen adsorption under high-temperature, high-pressure conditions.

Herein, we developed a precursor approach toward the design of a titanium nitride (TiN)/silicon nitride (Si3N4) nanocomposite with an activated carbon monolith as a support matrix forming a highly micro-/mesoporous component to be used as a Pt support for the catalytic hydrolysis of sodium borohydride (NaBH4) as a model reaction. The experimental data demonstrated that the amorphous Si3N4 matrix, the strong Pt-TiN nanocluster interaction and the synergistic effects between the three components contributed to the improved performance of the catalyst system. Thus, the use of this TiN/Si3N4 nanocomposite allowed to significantly reducing the noble metal loading (only ∼1 wt% of Pt) for the complete and fast dehydrogenation of NaBH4 under alkaline conditions at 80 °C. Additionally, the catalytic system displayed an excellent robustness and durability to offer reusability without collapsing and performance decrease under the harsh conditions imposed by the reaction.

Alkali hydrazinidoboranes MN2H3BH3 (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN2H3BH3, we focused on cesium hydrazinidoborane CsN2H3BH3 (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N2H4BH3) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P21 (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min−1) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH3, B2H6) together with H2, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O2/H2O. Though the destabilization brought by Cs+ onto the anion [N2H3BH3]− has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage.

International audience; Boron nitride, BN, for hydrogen storage emerged in the beginning of the millennium and there swiftly followed more than 15 years of efforts combining experimental laboratory works and to a greater extent computational predictions. BN has been considered mainly for the storage of molecular hydrogen, H-2, by physisorption and/or chemisorption over a wide range of temperatures, that is, between -196 degrees C and 300 degrees C. Yet its potential has gone beyond the sorption of H-2 as it has been also, although less extensively, involved in chemical H storage. The present review aims at giving a comprehensive overview of the main experimental results and findings as well as of the different avenues worth being explored. A key lesson of this survey is that boron nitride may turn out to be a promising material for hydrogen storage at room conditions provided all the predictions come true. The "ball" is now in the lab experimenters' court.

International audience; Mesoporous monolithic (3D) boron nitride (BN) structures are synthesized using a template‐assisted polymer‐derived ceramic route. Polyborazylene is selected to impregnate monolithic activated carbon, which is used as template. After pyrolysis and template removal, this method supplies BN compounds with controlled crystallinity and tunable textural properties controlled by the temperature at which they have been annealed (from 1000 to 1450 °C). Monoliths with an interconnected mesoporous network, high specific surface areas from 584 to 728 m2 g−1, significant pore volumes from 0.75 to 0.93 cm3 g−1, and a relatively high compressive strength are generated. These highly porous compounds are used as nanoscaffolds to confine ammonia borane (AB). The composites provide an effective gravimetric hydrogen capacity of up to 8.1 wt %, based on AB measured at 100 °C; this value demonstrates the high potential of this system as a safe potential hydrogen storage material.

Viewing calcium hydrazinidoborane Ca(N2H3BH3)2 (9.3 wt% H) as a potential hydrogen storage material, we long sought to synthesize it by solid-solid reaction of calcium hydride CaH2 and hydrazine borane N2H4BH3. However, it was elusive because of unsuitable experimental conditions. In situ synchrotron thermodiffraction helped us to identify the key role played by the temperature in the formation of the new phase. From 45 °C, new diffraction peaks appear, and the DSC analysis shows an exothermic signal. Thermal activation is thus required to make solid-state CaH2 react with melted (liquid-state) N2H4BH3. The XRD pattern can be indexed using a mixture of two phases: (i) unreacted CaH2 as a minor phase (29 wt%) and (ii) the hitherto elusive Ca(N2H3BH3)2 (71 wt%). The as-formed Ca(N2H3BH3)2 crystallizes in a monoclinic Ic (No. 9) unit cell where the intermolecular interactions form chains (layers) along the a axis, resulting in intra-chain and inter-chain Ca⋅⋅⋅Ca distances as short as 4.39 and 7.04 A respectively. Beyond 90 °C, Ca(N2H3BH3)2 decomposes, as evidenced by the diffraction peaks fading, an exothermic signal revealed by DSC, a weight loss (5.3 wt% at 200 °C) observed by TGA, and a gas release (H2, and some N2, NH3, N2H4) monitored by MS. The as-formed thermolytic residue is amorphous and of complex polymeric composition. These results and the next challenges, are discussed herein.

The potential of the decahydro-closo-decaborate anion B10H102− in alkaline aqueous solution as anodic fuel was investigated by using cyclic voltammetry and three different bulk metal electrodes (platinum, gold and silver). The sodium salt NaB10H10 was first synthesized, fully characterized and assessed for its relative stability in alkaline medium for 25 days. Then, oxidation of B10H102− in alkaline aqueous solution was studied. With platinum, the electrochemical activity is nil. With gold and silver, oxidation takes place at >0 V vs. SCE, suggesting direct oxidation of B10H102−. A current density of e.g. 15.1 mA cm−2 at 0.51 V vs. SCE is produced, supporting an electrocatalytically activity for both electrodes. There is even some reversibility of the process (i.e. reduction of intermediate species) with silver. The most important oxidation products were identified as being B7-based anions for both silver and gold. Such results suggest the occurrence of partial oxidative degradation of B10H102− at positive potential and may open new application prospects to polyborate anions.

In this work we present rubidium hydrazinidoborane RbN2H3BH3 (RbHB), the newest and last member of the alkali metal derivatives of hydrazine borane N2H4BH3 (HB). It is shown that HB readily reacts with metallic rubidium in THF at room temperature to form RbHB under argon atmosphere. The molecular and crystal structures of this new compound are discussed on the basis of FTIR spectroscopy, 11B MAS NMR spectroscopy, and powder X-ray diffraction analyses. RbHB crystallizes in a monoclinic P21 (No. 4) unit cell where each Rb+ cation adopts octahedral coordination surrounded by six [N2H3BH3]− anions, which are two more than for e.g. LiN2H3BH3 (with tetrahedral coordination) in accordance with the larger size of Rb+. RbHB is isostructural to potassium hydrazinidoborane KN2H3BH3. Its dehydrogenation properties, evaluated by using thermogravimetric analysis, differential scanning calorimetry, and isothermal analysis, are compared to those of the parent HB as well as to analogous compounds in order to evaluate the potential of RbHB as hydrogen storage material. According to the presented data, the dehydrogenation properties of RbHB are much better than those of HB and are comparable to those of the lithium derivative. Our main results are reported therein.

International audience; The five-coordinate Ru-II hydride ((PNN)-P-tBu*) RuH(CO) (2) containing the dearomatized anionic form of the tridendate unsymmetrical pincer ligand (PNN)-P-tBu {(PNN)-P-tBu = 2-((di-tert-butylphosphino) methyl)-6-(3,5-dimethyl- 1H-pyrazol-1-yl) pyridine} has been exploited as an ammonia borane (NH3 center dot BH3, AB) and hydrazine bis(borane) (H3B center dot H2N-NH2 center dot BH3, HBB) dehydrogenation catalyst in THF solution at ambient temperature. Complex 2 releases two H-2 equivalents per AB monomer and 1.5 H-2 equivalent per HBB monomer, with concomitant generation of the corresponding polymeric "spent fuels" [poly(borazylenes) or poly(aminoboranes), respectively]. Complex 2 has been found to have excellent catalytic activity, with recorded TOF values of 171 h(-1) (AB) and 359 h(-1) (HBB) at ambient temperature. The reaction has been studied experimentally through multinuclear [11B, 31P{1H}, and 1H] variable-temperature (VT) NMR spectroscopy, kinetic rate measurements and kinetic isotope effect (KIE) determination with deuterated AB isotopologues. It was found that the pincer backbone is directly involved in the catalytic process, with the presence of both protonated ((PNN)-P-tBu) and deprotonated ((PNN)-P-tBu*)(-) forms in solution. Cooperative catalysis involving the pincer methylenic side-arm and the metal center at the same time is the most likely reaction mechanism, on the basis of the collected experimental data and the computational analysis of the process at the DFT//MN15//SMD level of theory. An unprecedented dearomatization path stemming from the reduction of Cg of the pyridine central ring has been found in the catalyst spent form formed at the end of the dehydrogenation process: ((PNN)-P-tBu#) RuH(CO)center dot BH3 (4). Complex 4 was independently synthesized from the hydrido-chloro compound ((PNN)-P-tBu) RuH(CO) Cl (1) with a large excess of NaBH4 at solvent reflux and it was characterized both in solution and in the solid state. The crystal structure revealed that the borane " ligand" bridges the Ru center and the pyridine N atom through one of its B-H bonds in a s-BH agostic fashion. It can be formally considered as a (more stable) structural isomer of the hydride-borohydride complex ((PNN)-P-tBu) RuH(CO)(eta(1)-BH4) (3), with the H and BH4 ligands trans to each other within the octahedral metal coordination sphere.

International audience; As the world shifts toward renewable energy, the need for an effective energy carrier is pressing. Hydrogen has often been touted as a universal clean energy vector and the fuel of the future. Unfortunately, mass adoption of the hydrogen economy is slow due to a lack of incentives and technical difficulties in storing hydrogen. Better materials capable of reversible hydrogen uptake/release with hydrogen capacity surpassing 5 mass% at the ambient must emerge. So far, finding such materials has been elusive; alloys capable of ambient hydrogen uptake/release have a low storage capacity while high capacity hydrides have a very high hydrogen release temperature. From metal alloys to complex hydrides, a better understanding of the behavior of hydrogen in hydrides is essential to fine-tune their properties toward application. Herein, the latest approaches to design hydrogen storage materials based on known hydrides are reviewed with the aim to facilitate the emergence of alternative thinking toward the design of better hydrogen storage materials. Synthetic methods and conceptual approaches to achieve particular hydrogen thermodynamics and kinetics are discussed. These include metallurgical alloying, mechanochemical modification, chemical destabilization, the nanosizing approach, and theoretical modeling and machine learning techniques to guide experimental work.

Nickel complexes have recently been presented as prospective catalytic materials for hydrogen H2 evolution by hydrolysis of sodium borohydride NaBH4. An attractive complex is nickel hydrazine nitrate [Ni(N2H4)3][NO3]2 for which little variations in the synthesis procedure result in different morphologies like hexagonal plates, clews and discs. In our conditions, the clews have the better catalytic activity owing to more defects and more active sites. There is an effect of the morphology on the catalytic activity. However, the H2 evolution curves (regardless the initial morphology) show an induction period during which the complex (purple violet in color) evolves into a catalytically active form (fine black powder). The evolution is featured by changes in morphology and chemical state of nickel. The catalytically active form is even more active than the pristine complex: it shows a higher H2 generation rate (three times higher in the best case). The starting complexes and the “reduced” counterparts have been then characterized (e.g. SEM, FTIR, XRD, XPS) to better understand the aforementioned evolutions. One of our main conclusions is that there are some marked analogies between our nickel-based catalysts and the much-investigated cobalt-based catalysts.

Catalyzed hydrolysis of sodium borohydride generates up to four molecules of hydrogen, but contrary to what has been reported so far, the humidified evolved gas is not pure hydrogen. Elemental and spectroscopic analyses show, for the first time, that borate by-products pollute the stream as well as the vessel.

International audience; Ammonia borane NH3BH3 is a well-known thermolytic hydrogen storage material. However, the mechanism of dehydrogenation under heating is very complex. In this context, we have studied the thermolytic dehydrocoupling of solid, partially deuterated, ammonia borane NH3BD3 up to 200 degrees C, that is, up to the release of the second equivalent of hydrogen, by using thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry. Our results show that the process, resulting in the release of hydrogen (i.e., HD), is mainly driven by heteropolar hydrogen-deuterium interactions (N-H delta+center dot center dot center dot D delta--B). Homopolar dihydrogen interactions (N-H delta+center dot center dot center dot H delta+-N) appreciably contribute to hydrogen (i.e., H-2) release. In contrast, the contribution of homopolar dideuterium interactions (B-D delta-center dot center dot center dot D delta--B) is negligible. In summary, this work sheds new light on the mechanism governing the release of hydrogen from ammonia borane under thermolytic conditions.

International audience; Nickel-based bimetallic catalysts were screened using the sodium borohydride NaBH4 hydrolysis and the aqueous hydrazine borane N2H4BH3 dehydrogenation. A total of 22 bimetallic catalysts were synthesized according to an easy process while focusing on metals like Fe, Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt and Au. In the end, the bimetallic candidate Ni87.5Pt12.5 showed to be the most active and the most selective for the dehydrogenation of N2H4BH3. At 70 degrees C, it is able to decompose N2H4BH3 into 5.8 equivalents of H-2+N-2 in less than 12 min such as: N2H4BH3 + 3H(2)O -> 0.95 N-2 + 0.1 NH3 + B(OH)(3) 4.85H(2). Durability and stability tests were also performed. In our conditions, Ni87.5Pt12.5 was found to suffer from small loss of performance because of an electronic evolution of the catalytic surface leading to modified sorption properties of the catalytic sites. Our main results are reported and discussed herein

Herein, we provide a detailed insight into the precursor chemistry, precursor-to-material transformation and characterization of nanocomposites made of a TiN nanophase and a Si-O-C-N ceramic. The polymer-derived ceramics (PDCs) route applied to synthesize these nanocomposites resulted in the formation of nanocrystals less than 4 nm in size and the calculated lattice parameter value for the nanocrystals (a = 0.4239 nm) matched the theoretical value of TiN (a = 0.4241 nm). The Si-O-C-N ceramic served as a platform for anchoring TiN nanocrystals. As a proof of concept, we have attempted to exploit the plasmonic properties of nanocomposites to achieve photocatalytic degradation of organic dyes. The absorption spectra clearly showed plasmonic resonance in the visible region with peak positioned around 670 nm according to the presence of TiN nanocrystals which resulted in the enhancement of dye degradation. Keywords: Nanocomposites, Plasmonics, Photocatalysis, Dyedegradation

International audience; In the recent years, polyborate anions have been considered as possible candidates for energy. In aqueous solutions, they have been studied as either hydrogen carriers or anodic fuels. In the solid state (as an alkali salt), they have been seen as solid electrolytes. Herein, we focus on sodium 1-oxa-nido-dodecaborate NaB11H12O, a novel possible candidate for the aforementioned applications. The compound is soluble in water, and its stability depends on pH: under acidic conditions, it readily hydrolyzes while liberating hydrogen, and under alkaline conditions, it is stable, which is a feature searched for an anodic fuel. Over bulk platinum, gold, or silver electrode, oxidation takes place. The best performance has been noticed for the silver electrode. In the solid state, NaB11H12O shows Na+ conductivity at a high temperature of up to 150 °C. All of these properties are presented in detail, and hereafter they are discussed while giving indications of what have to be developed to open up more realistic prospectives for NaB11H12O in energy.

International audience; he scientific and technological challenges of energy-related fields are mainly associated with the emergence of new, advanced knowledge and fundamental understanding of materials. In the different categories of materials, ceramics offer a unique combination of physical and chemical properties making them key contributors for energy production/conversion and storage applications. The Polymer-Derived Ceramics (PDC) route enables the synthesis of such materials with an excellent control of the porosity at mesoscopic length scale offering potentialities as support materials to anchor and disperse active metals or for a direct use as catalysts. This review proposes an overview of the works related to the design of mesoporous PDC in the last 15 years. A particular focus is made on the forming methods which have been associated with the PDC route to engineer the mesoporosity and the shape of ceramics derived from preceramic polymers. The main topics reviewed are related to the processing of tailor-made polymeric precursors to mesoporous components, and to the characterization of the material properties. The two strategies adopted for the development of the catalytic activity of mesoporous PDC, i.e., deposition of metal nanoparticles on the mesoporous network or in-situ generation of the catalytically active phase in the mesoporous PDC matrix, are presented. Their recent application in various catalyst-assisted reactions is then discussed. Additionally, we outline the current challenges on the field of mesoporous PDC and provide perspectives on the need for further advances in mesoporous PDC.

International audience; Ammonia borane NH3BH3 (AB) and nickel (Ni) have been considered together as an all-solid and all-in-one material for H-2 generation by hydrolysis at 20-50 degrees C. Our novel approach, denoted Ni/AB, consists of AB nanoparticles within a Ni matrix. Upon contact with water, Ni/AB readily hydrolyzes and liberates H-2 with a turnover frequency of 13.8 mol(H-2) mol(Ni)(-1) min(-1) at 43.3 degrees C. The apparent activation energy, determined over the temperature range 23.5-50.4 degrees C, is low, with 19.5 +/- 4.1 kJ mol(-1). These results imply that such a Ni matrix embedding AB acts as an effective catalyst. Beyond the catalytic performance, this is the first report of the successful utilization of an all-solid and all-in-one approach for the hydrolysis of AB, and the work brings unique perspectives for one-shot catalytic systems. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

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International audience; Sodium borohydride NaBH4 (SB) readily and completely reacts with four equivalents of propylene glycol HOCH2CH(OH)CH3 (PG), resulting in the liberation of four equivalents of H2 at temperatures starting from 25 °C. Alcoholysis (or glycolysis) takes place. The system SB-4PG is then an attractive H2 generator thanks to an effective gravimetric hydrogen storage capacity of 2.3 wt%. It offers several other advantages: there is no need of catalyst; there is no precipitation of by-product; PG is among the safest alcohols (much safer than e.g. methanol). The potential of SB-4PG as H2 generator is thus illustrated and discussed herein.

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Pd–MnO2–Fe2O3/C and Pd/C (for comparison to the former) were synthesized by NaBH4 reduction method and then annealed at 500 °C. The catalysts were characterized physically by various techniques including XRD, TEM, EDX, XPS and ICP. The results showed that both MnO2 and Fe2O3 are in the amorphous form while Pd is crystalline for both catalysts. The particle size of Pd nanoparticles in Pd–MnO2–Fe2O3/C and Pd/C catalysts were found to be 11.6 nm and 10.9 nm, respectively. The total metal weight percent in Pd–MnO2–Fe2O3/C was determined as 18% and the metal molar ratios of Pd:Mn:Fe was calculated as 49:20:31. By cyclic voltammetry (CV) and chronoamperometry (CA), the ternary catalyst showed a superior electrocatalytic activity, namely of ≈3.4 times higher than Pd/C. The results also indicated that amorphous third parties may play a crucial role to improve the catalyst activity towards formic acid oxidation. All of these results are reported and discussed in details herein.

The 2000–2013 literature (through 260 research articles) dedicated to the field of “the hydrogen cycle with hydrolysis of sodium borohydride” was statistically analyzed. The objectives were (i) to emphasize the imbalance of the efforts dedicated to different aspects of the hydrogen cycle, (ii) to highlight the scientific/technical issues to prioritize from now on, and (iii) to revive an image tarnished since 2007. The statistical analysis was performed in terms of form and content. With respect to the form, it stands out for example that: the principal journal in the field is International Journal of Hydrogen Energy; the Chinese institutions are the most active; Turkey is also much involved while the most abundant reserves of boron can be found in this country. In terms of content, it is shown that there is unequivocal imbalance in the efforts dedicated to e.g. catalysis, borates recycling and scale-up. Huge attention has been focused on catalysis. The other topics were somehow neglected. Catalysis is not a critical issue anymore. Hence, recycling definitely merits much more interest, particularly to address the cost issue. A potential solution to explore is suggested herein. Scale-up is also imperative as it is the only way to demonstrate the technological potential of “the hydrogen cycle with hydrolysis of sodium borohydride”, to which one can optimistically believe. All of these aspects, among others, are discussed herein.

International audience; Late transition metal have attracted considerable interest for catalytic applications. Their immobilization over supports with tailored porosity is advantageous for nanosizing metal particles and avoiding their agglomeration which is known to bring a serious issue to the catalytic performance. Herein, ordered mesoporous silicon nitride (Si3N4) nanoblocks with hexagonal symmetry of the pores, high specific surface areas (772.4 m2 g−1) and pore volume (1.19 cm3 g−1) are synthesized by nanocasting using perhydropolysilazane as precursor. Then, Si3N4 nanoblocks are used as supports to synthesize platinum nanoparticles (Pt NPs) by precursor wet impregnation. Detailed characterizations by TEM show that monodispersed spherical Pt NPs with a 6.77 nm diameter are successfully loaded over nanoblocks to generate nanocatalysts. The latter are subsequently used for the catalytic hydrolysis of sodium borohydride (NaBH4). A hydrogen generation rate of 13.54 L min−1 gPt−1 is measured. It is notably higher than the catalytic hydrolysis using Pt/CMK-3 nanocatalysts (2.58 L min−1 gPt−1) most probably due to the textural properties of the Si3N4 supports associated with the intrinsic properties of Si3N4. This leads to an attractive nanocatalyst in pursuit of practical implementation of B-/N-based chemical hydrides as a hydrogen source for fuel cell application.

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Representatives of B−(N−)H hydrogen carriers are alkali borohydrides ( e.g. LiBH 4 and NaBH 4 ) and amine boranes ( e.g. NH 3 BH 3 and NaNH 2 BH 3 ). These are old compounds; they were discovered in the first half of the 20th century. One of the main contributors to their development is Prof. Hermann I. Schlesinger (1882–1960). In the recent years, there has been new interest in these old compounds as novel chemical H storage materials. Sodium borohydride NaBH 4 is a typical example. It was discovered by Schlesinger and collaborators in the 1950s. At that time it was found to be an attractive H 2 generator; owing to this property it reemerged in the early 2000s for on-board H 2 generation. Today, Schlesinger is commonly considered as the pioneer of NaBH 4 as hydrogen carrier but the impact of Schlesinger and collaborators' discoveries upon the course of modern chemistry on B−(N−)H hydrogen carriers is far more extensive … This is highlighted herein.

In the field of “hydrogen energy”, sodium borohydride (NaBH4) is a potential hydrogen carrier able to release H2 by hydrolysis in the presence of a metal catalyst. Our laboratory experiment focuses on this. It is intended for third-year undergraduate students in order to have hands-on laboratory experience through the synthesis of Co–Cu catalysts, X-ray characterization, and catalytic tests to qualitatively illustrate the Sabatier principle (volcano plot). The experiments require minimal preparation and are simple and instructive. Students gain experience in handling H2 and a better understanding of the current issues hindering the development of the “hydrogen economy”.

Ammonia borane H3N BH3, first reported in 1955, is isoelectronic with ethane H3C CH3, but it has much different properties owing to (i) the nitrogen and boron atoms (leading to a dipole moment), (ii) the protic and hydridic hydrogens, and (iii) the heteropolar dihydrogen bonding (rationalizing its solid state at ambient conditions). Ammonia borane has exceptional properties for chemical hydrogen storage and the recent years have witnessed many efforts in making it implementable for both thermolytic and hydrolytic dehydrogenations. The present article aims at (1) giving an exhaustive overview of the 1955–2016 literature dedicated to ammonia borane's fundamentals and exceptional properties, and then (2) surveying the main achievements, limitations and challenges for chemical hydrogen storage.

Herein we present and discuss the catalytic activity results of nickel-based bimetallic nanoparticles towards the two-step dehydrogenation of hydrazine borane N 2 H 4 BH 3 . Cobalt, iron and palladium were chosen as the second metal, and a series of Ni 1− x M x nanocatalysts were prepared by surfactant-aided co-reduction method. The challenge was to find a nanocatalyst that is active in the decomposition of the N 2 H 4 moiety of hydrazine borane. Of the 14 Ni 1− x M x combinations, the best results were achieved with Ni 0.7 Fe 0.3 and Ni 0.7 Pd 0.3 . At 50 °C, 3.9 and 4.3 mol H 2 + N 2 per mole of N 2 H 4 BH 3 were measured, indicating an activity in the decomposition of the N 2 H 4 moiety. Then, both nanocatalysts were characterized by XRD, SEM, EDX, TEM, SAED and XPS. Finally, the differences in catalytic activity were discussed in terms of electronic and geometric effects.

In the field of solid-state chemical hydrogen storage, ammonia borane NH3BH3 has been widely studied while hydrazine borane N2H4BH3 can be considered as a “novel” material. In the present work, we investigated the behaviour of these boranes when mixed together in a mole ratio of 1:1. Hydrazine borane and ammonia borane destabilize each other. Though stable at 20–25 °C, the mixture melts at ∼30 °C and then undergoes significant decomposition, with desorption of hydrogen H2 and hydrazine N2H4 from 67 °C. This is explained by the fact that the presence of hydrazine borane disrupts the Hδ+⋯Hδ− network of ammonia borane, and vice versa; the mixture is then much less stable than the pristine boranes. The mixture can nevertheless be stabilized (by heat- or vacuum-treatment and thus extraction of evolving hydrogen and hydrazine), making the as-obtained solid a potential chemical hydrogen storage material. Over the range 25–300 °C, it is able to release ca. 11.4 wt% of almost pure H2. Furthermore forms boron nitride as the solid residue, at temperatures as low as 300 °C.

In the field of ‘hydrogen storage and generation’, ammonia borane NH 3 BH 3 (AB) destabilization can be achieved by adding a metal halide, here copper chloride (CuCl 2 ). Improved dehydrogenation properties can be achieved with a fresh mixture of CuCl 2 –NH 3 BH 3 . Using a systematic approach, we followed the stability of the mixture using thermogravimetric analysis, differential scanning calorimetry and (micro) gas chromatography while it was stored under argon at room temperature over 6 months. The aged samples showed improved dehydrogenation properties compared to pristine AB. However, the performance deteriorated in comparison to the fresh mixture indicating that CuCl 2 –NH 3 BH 3 evolves over time, decomposing with slow kinetics. This is detrimental in terms of stability during storage, making long-term storage of CuCl 2 inconceivable for safety and performance reasons. This is discussed herein.

Hydrogen, H2, is one of the most promising (bio-)fuels for our near-future as it is considered as a green energy carrier. However, its natural occurrence is extremely low. In fact, it has to be produced through various processes, from various sources, given that atomic hydrogen, H, exists combined with other light atoms, e.g. oxygen in water, carbon in methane, or both atoms in cellulose. As molecular hydrogen has to be produced, the relative greenness of the production processes merits analysis; we do this here qualitatively. The analysis is notably based on the 12 principles of green chemistry. After an overview of the main hydrogen processes, we show that the combination of renewable raw materials with biological or electrochemical methods and with renewable energies, makes hydrogen production “green”.

Herein, we present the successful synthesis and full characterization (by 11B magic-angle-spinning nuclear magnetic resonance spectroscopy, infrared spectroscopy, powder X-ray diffraction) of sodium hydrazinidoborane (NaN2H3BH3, with a hydrogen content of 8.85 wt%), a new material for chemical hydrogen storage. Using lab-prepared pure hydrazine borane (N2H4BH3) and commercial sodium hydride as precursors, sodium hydrazinidoborane was synthesized by ball-milling at low temperature (-30 °C) under an argon atmosphere. Its thermal stability was assessed by thermogravimetric analysis and differential scanning calorimetry. It was found that under heating sodium hydrazinidoborane starts to liberate hydrogen below 608C. Within the range of 60-150 °C, the overall mass loss is as high as 7.6 wt%. Relative to the parent N 2H4BH3, sodium hydrazinidoborane shows improved dehydrogenation properties, further confirmed by dehydrogenation experiments under prolonged heating at constant temperatures of 80, 90, 95, 100, and 110°C. Hence, sodium hydrazinidoborane appears to be more suitable for chemical hydrogen storage than N2H4BH3. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid-state ammonia borane H 3 N BH 3 (AB) is attractive for chemical hydrogen storage owing to 19.5 wt% of hydrogen in protic and hydridic forms. As part of our efforts dedicated to revisit the fundamentals of AB, we herein report the results of a work focusing on twelve samples synthesized according to two pathways using various precursors and different experimental conditions. The AB samples were characterized by XRD, FTIR and NMR, and especially screened by TGA in identical operating conditions (allowing direct comparison). For all samples, differences in terms of reactivity of the precursors, yield and purity were noticed. For the purest samples, dissimilarities in terms of thermolytic properties and stability were even observed. For example, onset temperatures of decomposition of 116.5 and 98 °C were found. This could be the result of discrepancies in interactivity and reactivity of the solid-state precursors, and the interactivity and reactivity would be driven by electronic and/or geometric effects. In other words, thermolytic properties and stability of AB can be tuned to by optimizing synthesis conditions.

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Herein, mesoporous 3D silicon carbide (SiC), carbonitride (Si C N) and nitride (Si3N4) structures have been synthesized by nanocasting and pyrolysis using commercial organosilicon polymers as precursors of the different compositions. Detailed characterizations by BET and XRD allowed us to fix the most appropriate parameters to design mesoporous 3D structures with high specific surface areas and high pore volume. Then, the series of 3D structures has been used as supports to grow platinum nanoparticles (Pt NPs) by wet impregnation followed by reduction in hydrogen/argon flow. The Pt-supported mesoporous 3D supports kept the mesoporosity of the virgin supports to be used for catalytic hydrolysis of sodium borohydride (NaBH4). A hydrogen generation rate of 24.2 L min−1 gPt−1 is measured for the Pt-supported mesoporous 3D Si3N4 structure, which is notably higher than the catalytic hydrolysis using Pt-supported mesoporous 3D SiC and Si C N structures. HRTEM investigations demonstrated the homogeneous distribution of Pt NPs over the Si3N4 support.

The boron (Z = 5) element is unique. Boron-based (nano-)materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-)materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes and carboranes, boronate anions/ligands, boron nitride (hexagonal structure), and elemental boron are considered. Importantly, large sections are dedicated to fundamentals, with a special focus on crystal structures. The application potentials are widely discussed on the basis of the materials’ physical and chemical properties. It stands out that crystalline boron-based (nano-)materials have many technological opportunities in fields such as energy storage, gas sorption (depollution), medicine, and optical and electronic devices. The present special issue is further evidence of the wealth of boron science, especially in terms of crystalline (nano-)materials.

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.

The progress of hydrogen generation by sodium borohydride hydrolysis depends highly on the development of efficient catalysts based on non-noble metals such as cobalt. However, such catalysts undergo extensive deactivation which has a detrimental effect on their stability. Herein, highly porous copper and cobalt-based bimetallic foams, Cu x Co 100−x (x = 0–100 at%), produced by electrodeposition using the dynamic hydrogen bubble template are reported. The chemical composition of the foams was optimized in order to enhance specific surface area and improve their catalytic activity and stability as heterogeneous catalysts for sodium borohydride hydrolysis. Among the tested catalysts, copper-rich samples like Cu 85 Co 15 are slightly more active than Co 100 and above all, they are less sensitive to deactivation by borates adsorption. Porous copper-rich foams were found to be an alternative to cobalt as low-cost, active and stable heterogeneous catalysts for hydrogen generation by hydrolysis of sodium borohydride.

SSCI-VIDE+CARE:CDFA+VCN:MTS:PVE; International audience; We report here the solution coatings of Diesel Particulate Filter (DPF) with allylhydridopolycarbosilane (AHPCS)-based polymers leading tosupported silicon carbide (SiC)-based membranes with high temperaturesoot particle filtration efficiency, durability and catalytic activity.In a first part of the present study, our objective was to reduce thepore size of DPF to filtrate finer particles without altering filtrationefficiency by coating DPF with an additional fine porous AHPCS-derivedSiC membrane. The latter is produced by dip-coating AHPCS on DPFfollowing by a pyrolysis of the AHPCS membrane-modified DPF at 1000degrees C under argon. We investigated the influence of dip-coatingparameters and viscosity of different AHPCS solutions on the SiCmembrane-coated DPF by SEM, mercury porosimetry, XRD andhigh-temperature thermogravimetric analysis. The evolution of thefiltration capacity has been determined with a synthetic gas bench. Anadditional fine SiC membrane (-150 nm in thickness) prepared from a 10vol% of AHPCS in THE deposited on DPF allowed maintaining filtrationefficiency as high as the virgin DPF while the pore size of the SiCmembrane coated-DPF decreased to filter finer particles. Results areconfirmed using a commercially-available polysiloxane (Si-C-Oprecursor). Furthermore, the SiC membrane acted as a thermal barriercoating and provided a better durability to the DPF by preventingapparition of cracks after heat-treatment to 1500 degrees C under argon.The use of mixed oxide and metallic phases formed in-situ in SiCconstitutes one of the solutions to generate new and effective catalyticperformances to membranes. Within this context, in a second part of thestudy, we applied a reverse AHPCS-based microemulsion to combine SiCand oxide phases in the same additional porous membrane. As a proof ofconcept, we have prepared catalytically active Ce-O-Fe-Pt/SiC membranecoated DPF after dip-coating and pyrolysis under argon. These materialshave been characterized and tested with regard to CO/HC oxidation andsoot combustion. Ce-O-Fe-Pt/SiC membrane coated DPF showed an activityfor CO conversion reaching a light off temperature T-50=270 degrees Cand the presence of the catalytic phase allowed burning soot at 486degrees C. (C) 2015 Elsevier B.V. All rights reserved.

International audience; Today there is a consensus regarding the potential of NaBH4 as a good candidate for hydrogen storage and release via hydrolysis reaction, especially for mobile, portable and niche applications. However as gone through in the present paper two mains issues, which are the most investigated throughout the open literature, still avoid NaBH4 to be competitive. The first one is water handling. The second one is the catalytic material used to accelerate the hydrolysis reaction. Both issues are object of great attentions as that can be noticed throughout the open literature. This review presents and discusses the various strategies which were considered until now by many studies to manage water and to improve catalysts performances (reactivity and durability). Published studies show real improvements and much more efforts might lead to significant overhangs. Nevertheless the results show that we are still far from envisaging short-term commercialization.

In the present work, seven samples of cerium oxide-based binary and ternary nanoparticles were prepared by a micro emulsion technique to be used as catalysts for carbon and soot oxidations. Pure CeO2, binary CeO2–Fe2O3 (with different oxide contents) and Pt–CeO2–FeO3 were targeted. Preliminary characterizations by EDX, XRD and N2 sorption confirmed the formation of nanosized crystallites. The oxidation experiments performed by TGA allowed screening the catalysts. Three of them were then selected: CeO2 as a reference, Pt12Ce88 and Pt6Ce90Fe4. TEM confirmed the nanometric size of the particles and showed aggregation. XPS suggested Ce3+, Ce4+ and active oxygen (O2− and O−) as surface species, which are important in the oxidation of carbonaceous compounds. Finally, the Pt-doped samples were scaled up by coating onto the surface of unplugged mini silicon carbide monoliths and tested for oxidation of hydrocarbons and carbon monoxide. Coating was performed by dip-coating. Attractive performance was found. Our main results are reported and discussed herein.

Cobalt is the most attractive catalyst for hydrogen generation from the hydrolysis of sodium borohydride, NaBH4, but its potential is further improved when it is combined with an inactive element like copper. Accordingly, several cobalt–copper catalysts (CoxCu1−x, with x as a mole ratio equal to 0, 0.1, 0.25, 0.5, 0.75, 0.9 or 1) were prepared. Under our conditions, Co0.9Cu0.1 shows the best performance, being able to complete H2 evolution in

In the present work, the behavior of hydrazine borane N 2 H 4 BH 3 in the presence of alkali/alkaline-earth hydrides is investigated. ( i ) Hydrazine borane N 2 H 4 BH 3 is readily destabilized by an alkali hydride MH (M=Li, Na, K). The electronic properties of M drive the reactivity of MH 1 towards N 2 H 4 BH 3 . KH is the most reactive (at 25 °C, Δ r H = −70.25 kJ mol −1 ) while K is the least electronegative and the biggest element. Hydrazinidoboranes MN 2 H 3 BH 3 form. ( ii ) Hydrazine borane N 2 H 4 BH 3 is destabilized by MH x ( x = 2, 3; M=Mg, Ca, Al). In comparison to pristine N 2 H 4 BH 3 , better dehydrogenation properties are found: MgH 2 has a catalytic effect; CaH 2 strongly destabilizes N 2 H 4 BH 3 ; and, unstable AlH 3 is able to destabilize N 2 H 4 BH 3 under heating. Though the synthesis of hydrazinidoboranes M(N 2 H 3 BH 3 ) x is difficult, the mixtures MH x –N 2 H 4 BH 3 leads to composites. The most efficient composite is CaH 2 –N 2 H 4 BH 3 . The aforementioned hydrazinidoboranes and composites may have potential as solid-state hydrogen storage materials. This is discussed herein.

Alkaline fuel cells are interesting alternatives to proton-exchange membrane fuel cells, owing to the possibility to feed them directly with complex fuels (such as ethanol, methanol, ammonia, hydrazine, sodium borohydride, etc.) with acceptable performances. In that frame, studying the stability of carbon-supported catalysts nanoparticles in alkaline media is mandatory, these properties having largely been investigated in acidic electrolytes in the literature so far. Whether some works have focused on general aspects of carbon stability in alkaline media, to date none of them have investigated the stability of metal nanoparticles on carbon supports. Here, we studied the degradation of commercial (E-TEK) Pt and Pd nanoparticle electrocatalysts supported on Vulcan XC-72 (noted Pt/C and Pd/C) in NaOH electrolyte solutions, and compared the fate of the electrocatalysts to that in H2SO4, HClO4electrolyte solutions. Electrochemical measurements, combined with Identical-Location Transmission Electron Microscopy (ILTEM) allowed to demonstrate that the catalysts degradation in 0.1 M NaOH at 25°C is extremely severe for a mild accelerated stress tests (AST – 150 cycles, at 100 mV sec-1 and 25°C, between 0.1 and 1.23 V vs.RHE). The AST performed directly on TEM grids (Gold + Lacey carbon) for Pt/C in Identical-Location Transmission Electron Microscopy (ILTEM) imaging (Fig.1.a-b) demonstrated extensive nanoparticles loss (either by dissolution or detachment from the carbon surface) and non-negligible extent of agglomeration. These observations were further bridged with the results obtained with the CO-stripping technique (Fig.1.c), which clearly highlight the appearance of a pre-peak associated to the Pt agglomerates, features that are generally observed for much harsher and/or longer degradation protocols and at higher temperature value in acidic media1,2,3. As a result, the electrochemical surface area (ECSA) losses are about 3 times worse in alkaline than in acidic media (60 % of ECSA loss vs. ca. 20% in H2SO4 and HClO4, Fig.1.d) for such a “mild” AST. The effect of the electrocatalyst material nature (Pd or Pt) and size effects on the degradation profile and rate have also been investigated. In these harsh degradation in alkaline medium, extensive carbon corrosion has been ruled out, according to Raman spectroscopy measurements that show nearly no sign of structural changes of the carbon, although such effect is often observed in acidic media4. Therefore, we attributed the huge changes of Pt/C and Pd/C morphology upon AST in alkaline medium to the modification of the carbon surface carbon chemistry, in agreement with XPS measurements, which simply destroys the anchoring sites of the Pt (resp. Pd) nanoparticles and favors their simple detachment from the carbon surface. We also cannot rule out cathodic corrosion of the Pt (resp. Pd) nanoparticles at the lower vertex potential of the AST, as experienced by the group of Koper 5. References (1) F. Nikkuni, E. Ticianelli, L. Dubau, M. Chatenet, Electrocatal., 4 (2013) 104-116. (2) L. Dubau, L. Castanheira, G. Berthomé, F. Maillard Electrochim. Acta, 110 (2013) 273– 281. (3) Meier, J. C., Galeano, C., Katsounaros, I., Witte, J., Bongard, H. J., Topalov, A. a, Mayrhofer, K. J. J. (2014). Beilstein Journal of Nanotechnology, 5, 44–67. (4) Dubau, L., Castanheira, L., Chatenet, M., Maillard, F., Dillet, J., Maranzana, G., (2014). International Journal of Hydrogen Energy, 39(36), 21902–21914. (5) Yanson, A. I.; Rodriguez, P.; Garcia-Araez, N.; Mom, R. V.; Tichelaar, F. D.; Koper, M. T. M. Angew. Chem. Int. Ed. 2011, 50, 6346. Figure 1

Theoretically, sodium octahydrotriborate NaB3H8, solved in alkaline aqueous solution, is a potential boron-based liquid anodic fuel of direct liquid fuel cell, since the B3H8− anion could be oxidized (B3H8− + 20OH− → 3BO2− + 14H2O + 18e−) in a reaction ideally involving 18 electrons. Hence, we focus on this material. We firstly synthesize NaB3H8 and fully characterize it (NMR, FTIR, Raman, XRD, TGA, DSC), then study its stability in protic solutions by NMR, and lastly investigate its oxidation with the help of electrochemical techniques. The diffusion coefficient for the B3H8− anion is calculated (3.7·10−5 cm2 s−1) in order to assess the coulombic efficiency for the oxidation on platinum and gold electrodes. It is found effective numbers of electrons of 5.2 and 10.1 (out of a theoretical total of 18 electrons) respectively. Neither platinum nor gold smooth surfaces enable the complete oxidation of B3H8−, which is explained mainly by the occurrence of heterogeneous hydrolysis (i.e. hydrogen evolution), but also by the difficulty to break the B–B bonds (difficult to oxidize) present in the B3H8− anion. Yet, these first results confirm that the B3H8− anion has a potential as anodic fuel, provided the proper electrocatalyst is isolated: this is discussed herein.

In this work, we present the performance of “doped” sodium hydrazinidoborane NaN 2 H 3 BH 3 as hydrogen carrier. It was prepared by ball-milling hydrazine borane N 2 H 4 BH 3 and sodium hydride NaH in cold conditions, with an excess of 5 wt% of NaH. Such an excess is essential for the generation of pure hydrogen, i.e. free from the undesired by-products NH 3 and N 2 H 4 under heating, whereas for a material prepared in equimolar conditions non negligible amounts of ammonia NH 3 are detected. Our main results, i.e. characterization of “doped” sodium hydrazinidoborane, dehydrogenation experiments, analysis of the purity of H 2 , and characterization of the solid residue, are presented and discussed herein. The potential of “doped” sodium hydrazinidoborane as solid-state chemical hydrogen storage material is finally discussed.