3,3′-(Ethylenedioxy)dipropiononitrile (EDPN) has been introduced as a novel electrolyte additive to improve the oxidation stability of the conventional carbonate-based electrolyte for LiNi1/3Co1/3Mn1/3O2/graphite pouch batteries cycled under high voltage. Mixing 0.5 wt % EDPN into the electrolyte greatly improved the capacity retention, from 32.5% to 83.9%, of cells cycled for 100 times in the range 3.0–4.5 V with a rate of 1C. The high rate performance (3C and 5C) was also improved, while the cycle performance was similar to that of the cell without EDPN when cycled between 3.0 and 4.2 V. Further evidence of a stable protective interphase film can be formed on the LiNi1/3Co1/3Mn1/3O2 electrode surface due to the presence of EDPN in the electrolyte. This process effectively suppresses the oxidative decomposition of electrolyte and the growth in the charge-transfer resistance of the LiNi1/3Co1/3Mn1/3O2 electrode and greatly improves the high-voltage electrochemical properties for the cells. In contrast, EDPN has no positive effect on the cyclic performance of the LiNi0.5Co0.2Mn0.3O2-based cell under high operating voltage.Keywords: 3,3′-(ethylenedioxy)dipropiononitrile; cathode surface passivation; electrolyte additive; high voltage; LiNi1/3Co1/3Mn1/3O2/graphite;

Hydrogen generation is one of the enabling technologies for realization of hydrogen economy. In this study, we developed a high-performance hydrogen generation system using the transition metal Mo and its compounds (MoS2, MoO2, and MoO3) for catalyzing the hydrolysis of Mg composites in seawater. These Mg-based composites for the hydrolysis process were synthesized through a simple planetary ball mill technique. The results demonstrate that small amounts of added MoS2 could significantly accelerate and enhance the hydrolysis reaction of Mg in seawater. In particular, the Mg–10 wt% MoS2 composite releases 838 mL g−1 hydrogen in 10 min (about 89.8% of the theoretical hydrogen generation yield), and the recycled catalysts exhibit high cycle stability, which is the most significant achievement in this study. In addition, Mo, MoO2, and MoO3 also showed similar enhancement in the hydrolysis reaction of Mg. The activation energies for the hydrolysis of Mg decreased from 63.9 kJ mol−1 to 27.6 kJ mol−1, 20.4 kJ mol−1, 14.3 kJ mol−1, and 12.1 kJ mol−1 on introducing Mo, MoS2, MoO2, and MoO3, respectively. The attractive hydrolysis performance of the composites of Mg milled with Mo and its compounds in seawater may shed light on future developments of hydrogen generation technologies.

Reversible hydrogen storage has been found in transition metal alanates, Y(AlH4)3, for the first time. An amount of 3.4 wt% H2 can be released at 140 °C from the first dehydrogenation step of Y(AlH4)3, and 75% of it is reversible at 145 °C and 100 bar H2, which holds promise for low-temperature applications.

The synthesis and hydrolysis performance of NaZn(BH4)3 and its ammoniates were investigated in this paper. The successful synthesis of NaZn(BH4)3 and its ammoniates was confirmed by X-ray diffractometry and Fourier transform infrared spectroscopy measurements. The hydrolysis results show that NaZn(BH4)3 is able to generate 1740 mL g−1 hydrogen in 5 min and 1956 mL g−1 hydrogen in 30 min without concomitant release of undesirable gases such as ammonia or boranes. This rate can be too fast to be controllable in some hydrogen generation cases. In addition, it is found that NaZn(BH4)3·2NH3 generates 118 mL g−1 hydrogen in 5 min and 992 mL g−1 hydrogen in 2 h, accompanied by an emission of a small amount of ammonia. Furthermore, an enhanced hydrolysis performance can be achieved by formation of NaZn(BH4)3/NaZn(BH4)3·2NH3 composites. These composites synthesized via a planetary ball milling technique may generate hydrogen with a very reasonable and controllable speed of 717 mL g−1 hydrogen in 5 min and 1643 mL g−1 hydrogen in 2 h. The activation energies for the hydrolysis in deionized water of NaZn(BH4)3, NaZn(BH4)3·2NH3 and the NaZn(BH4)3/NaZn(BH4)3·2NH3 composite milled for 30 min were calculated to be 11.9 kJ mol−1, 56.9 kJ mol−1 and 32.5 kJ mol−1, respectively. These results demonstrate that the catalyst-free NaZn(BH4)3 and its ammoniates show better hydrolysis kinetics than other NaBH4 based materials and have the potential to be used as solid hydrogen generation materials.

Zr(BH4)4·8NH3 is considered to be a promising solid-state hydrogen-storage material, due to its high hydrogen density and low dehydrogenation temperature. However, the release of ammonia hinders its practical applications. To further reduce the dehydrogenation temperature and suppress ammonia release, here we investigated its hydrolysis process to evaluate its hydrogen generation performance. The results showed that the hydrolysis of Zr(BH4)4·8NH3 in water can generate about 1067 mL g−1 pure hydrogen in 240 min at 298 K without the release of diborane or ammonia impurity gases. With heat-assistance, the hydrogen generation rate can be significantly enhanced, and its activation energy was calculated to be 29.38 kJ mol−1. The hydrolysis mechanism was clarified. The results demonstrate that Zr(BH4)4·8NH3 may work as one promising hydrogen generation material.

•Porous carbon supported Fe-N-C composite was prepared as an ORR catalyst.•The pyrolysis temperature influences catalytic activity of the prepared catalyst.•The coordination of iron and nitrogen is key to achieve good ORR performances.•Fe-N-C-800 catalyst exhibits high catalytic activity and excellent stability.In recent years, non-precious metal electrocatalysts for oxygen reduction reaction (ORR) have attracted tremendous attention due to their high catalytic activity, long-term stability and excellent methanol tolerance. Herein, the porous carbon supported Fe-N-C catalysts for ORR were synthesized by direct pyrolysis of ferric chloride, 6-Chloropyridazin-3-amine and carbon black. Variation of pyrolysis temperature during the synthesis process leads to the difference in ORR catalytic activity. High pyrolysis temperature is beneficial to the formation of the “N-Fe” active sites and high electrical conductivity, but the excessive temperature will cause the decomposition of nitrogen-containing active sites, which are revealed by Raman, TGA and XPS. A series of synthesis and characterization experiments with/without nitrogen or iron in carbon black indicate that the coordination of iron and nitrogen plays a crucial role in achieving excellent ORR performances. Electrochemical test results show that the catalyst pyrolyzed at 800 °C (Fe-N-C-800) exhibits excellent ORR catalytic activity, better methanol tolerance and higher stability compared with commercial Pt/C catalyst in both alkaline and acidic conditions.Download high-res image (113KB)Download full-size image

•The maximum yield of NaBH4 (89%) is achieved by high-energy ball milling.•A two-step substitution mechanism for NaBH4 regeneration by MgH2 is first proposed.•An intermediate (NaBOH2) evidenced by NMR is formed during NaBH4 regeneration.In this paper, we developed an easy and simple method (high-energy ball milling) for recycling NaBO2 (the hydrolysis byproduct) back to NaBH4 by a reaction with MgH2. To optimize the yield of NaBH4, we investigated the effect of four parameters, e.g. the ball milling time, the molar ratio of MgH2/NaBO2, H2 pressure and addition of methanol, on the NaBH4 regeneration. Accordingly, the maximum yield of NaBH4 (89 wt. %) was achieved. The mechanism of NaBH4 regeneration has been discussed. It is indicated that the NaBH4 formation involves a two-step substitution in which NaBOH2 is an intermediate confirmed by solid-state nuclear magnetic resonance (NMR).Download high-res image (137KB)Download full-size image

•Fe/N/C carbon nanotubes with high nitrogen content were prepared as catalysts.•Fe–N–BCNTs-PPy-800 exhibited high catalytic activity and excellent stability.•The number of nitrogen active sites was increased by polymerization of pyrrole.The non-precious metal catalysts usually have low nitrogen content, resulting in poor oxygen reduction reaction (ORR) performance. Herein we demonstrated a strategy to synthesize the Fe/N/C carbon nanotubes (Fe–N–BCNTs) with high nitrogen content. The strategy included pyrolysis of ferric chloride and dicyandiamide, polymerization of pyrrole onto intermediate product's surface, and following by calcination in N2 atmosphere. Electrochemical test results show that the catalyst exhibits highly efficient ORR activity with an onset potential of 0.995 V (vs reversible hydrogen electrode) in 0.1 M KOH solution, 30 mV more positive than that of 20 wt. % Pt/C catalyst. The excellent ORR performances could be attributed to the more nitrogen functional groups in Fe–N–BCNTs-PPy-800 catalyst, which is revealed by Raman and XPS. Moreover, the prepared catalyst exhibits better methanol tolerance and higher stability in comparison to commercial Pt/C catalyst.Download high-res image (250KB)Download full-size image

•Few-layer graphene is successfully prepared via plasma-assisted ball milling.•The number of graphene layers can be controlled by varying the ball-milling media.•The suitable inductive capacity of ball-milling media stays at 7–8.We report a new method for few-layer graphene (FLG) preparation via plasma-assisted ball milling with carbide, nitride or oxides as ball-milling media and expandable graphite raw material. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy were applied to characterize the FLG. FLGs prepared by using different ball-milling media such as boron nitride (BN), tungsten carbide (WC), zinc oxide (ZnO), iron oxide (Fe2O3) and germanium oxide (GeO2) were used to determine the relationship between the FLG layer number and inductive capacity of the ball-milling media. Parameters for the synthesis of high-quality FLGs were also optimized.Download high-res image (224KB)Download full-size image

•The presence of transition metal oxides enhances the hydrolysis of magnesium.•Mg-5 wt% MoO3 composite produces 888 mL/g H2 in 10 min at 25 °C.•The valence state in Mg-Fex+ or Mg-Mox+ composites affect the hydrolysis properties.Mg is an attractive candidate for hydrogen generation due to its low cost and high availability as well as its high theoretical H2 yield and the formation of environmentally friendly byproducts during hydrolysis. On the other hand, the hydrolysis reaction of Mg is rapidly interrupted by the formation of a passive magnesium hydroxide layer. Hydrogen generation via the reaction of ball milled Mg-oxide composites with 3.5% NaCl solution at room temperature was investigated in this paper. Several cheap metal oxides (Fe2O3, CaO, MoO3, Fe3O4, Nb2O5 and TiO2) were used to assess the effects of hydrolysis on the magnesium powder. The results show that Mg-5 wt% MoO3 and Fe2O3 demonstrate the best hydrolysis performance (above 888 mL/g and 95.2% of theoretical hydrogen generation yield in 10 min) in comparison to MgFe3O4, MgTiO2, MgNb2O5 and MgCaO composites. In addition, the effects of different Mg contents and milling times on the hydrolysis property of the Mg powder were also studied and it was concluded that the addition of 5 wt% oxide and a milling time of 1 h are the optimal parameters for the production of the MgMoO3 composite. Moreover, the valence state of metal ions was found to have an important influence on the hydrolysis reaction for the first time. The effect of valence state has been studied for Mg-Fex+ and Mg-Mox+ composites and the results show that a higher valence value of the transition metal ions leads to a better hydrolysis property of Mg.

•The hydrolysis mechanism of H-CaMg2 and H-CaMg1.9Ni0.1 hydrides is clarified.•The hydrogen yield of H-CaMg2 is 800 mL/g with maximum hydrolysis rate of 2640 mL/(min g).•The fast and continuous hydrolysis of H-CaMg1.9Ni0.1 is due to the presence of Ca5Mg9H28 phase.•The value of Ea for H-CaMg1.9Ni0.1 is calculated to be 32.9 kJ/mol.Hydrogen generation via hydrolysis of hydrides from hydrogenated CaMg2 (abbreviated as H-CaMg2 hereafter) and hydrogenated CaMg1.9Ni0.1 (abbreviated as H-CaMg1.9Ni0.1 hereafter) alloys has been investigated in pure water without addition of any catalyst. Experimental results show that the hydrolysis of H-CaMg2 is fast when immersed in water with the hydrogen generation yield of 800 mL/g within 1 min. For CaMg1.9Ni0.1 alloy, the addition of Ni element spurs the hydrogen absorption at room temperature and significantly enhances the hydrolysis properties with fast and continuous hydrogen release yield of 1053 mL/g in 12 min, which is 94.6% of the theoretical hydrogen yield of H-CaMg1.9Ni0.1. The excellent hydrolysis properties of Ca5Mg9H28 and the catalytic effect of MgNi2 particles are further clarified. The fast and constant hydrolysis rate of H-CaMg1.9Ni0.1 can reach higher even than 365 mL/(min g) in first 2 min. The apparent activation energy of H-CaMg1.9Ni0.1 hydrolysis in deionized water is determined to be 32.9 kJ/mol. The hydrolysis mechanism of H-CaMg2 and H-CaMg1.9Ni0.1 was also discussed.

•Hydrogen is generated via the hydrolysis of NaBH4-ZnCl2 composites without catalysts.•The addition of ZnCl2 significantly increases the hydrolysis rate of NaBH4 and reduces the activation energy.•The hydrolysis behaviors are affected by milling time, temperature and the content of ZnCl2.•The hydrolysis kinetics and detailed hydrolysis processes were discussed.Sodium borohydride (NaBH4) hydrolysis offers significant advantages in hydrogen storage for fuel cells, but the hydrolysis requires the use of expensive catalysts, such as Ru and Pt alloys, or various supports. To explore low-cost and high activity catalysts, we use ZnCl2 to promote the hydrolysis rate of sodium borohydride. The mechanisms and apparent activation energy of these composites are discussed. Compared to the hydrolysis of pure NaBH4 (523 mL/g hydrogen in 2 h at 298 K), NaBH4 with 20 wt% ZnCl2 has the best hydrolysis performance with the hydrogen generation rates of 844 mL/g in 5 min, 1039 mL/g in 10 min and 1933 mL/g in 2 h at 298 K. The apparent activation energies of NaBH4 hydrolysis decreased from 79.5 kJ/mol in deionized water to 47.7 kJ/mol with the addition of 20 wt% ZnCl2. These results demonstrated that ZnCl2 could be a promising reagent to promote NaBH4 hydrolysis in a hydrogen generation system to replace noble metal catalysts.

•The mechanism is revealed for the phase transition of Mg-Ba compound during the de/hydrogenation process.•A new kind of fully reversible hydrogen storage Mg-Ba-H alloy is realized.•An undefined barium magnesium hydride has been found with composition being Ba2Mg7H18.Mg17Ba2 hydrogen storage alloy was obtained by induction melting, and its hydrogen storage properties and phase transitions have been investigated. The reversible hydrogen capacity of Mg17Ba2 compound was 4.0 wt% H2. A three-step dehydrogenation mechanism was revealed for the first time, and a new hydride (Ba2Mg7H18) was discovered during the dehydrogenation process. Enthalpy and entropy changes for the dehydrogenation of Mg17Ba2 were also calculated.Download high-res image (199KB)Download full-size image

•Air-stable hydrolysis material of MgH2-LiNH2 composites is studied for the first time.•The hydrolysis properties of MgH2 were significantly enhanced by introduction of LiNH2.•The hydrolysis mechanism of xMgH2-yLiNH2 composites is also reported.•Air-stable MgH2-LiNH2 system means easy handling and good practicability for hydrolysis.Hydrolysis of materials in water can be a promising solution of onsite hydrogen generation for realization of hydrogen economy. In this work, it was the first time that the MgH2-LiNH2 composites were explored as air-stable hydrolysis system for hydrogen generation. The MgH2-LiNH2 composites with different composition ratios were synthesized by ball milling with various durations and the hydrogen generation performances of the composite samples were investigated and compared. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy techniques were adopted to elucidate the performance improvement mechanisms. The hydrolysis properties of MgH2 were found to be significantly enhanced by the introduction of LiNH2. The 4MgH2-LiNH2 composite ball milled for 5 h can generate 887.2 mL g−1 hydrogen in 1 min and 1016 mL g−1 in 50 min, one of the best results so far for Mg based hydrolysis materials. The LiOH·H2O and NH4OH phases of hydrolysis products from LiNH2 may prevent formation of Mg(OH)2 passivation layer on the surface and supply enough channels for hydrolysis of MgH2. The MgH2-LiNH2 composites appeared to be very stable in air and no obvious negative effect on kinetics and hydrogen generation yield was observed. These good performances demonstrate that the studied MgH2-LiNH2 composites can be a promising and practicable hydrogen generation system.

•Catalytic properties of flower-like MoS2 on Mg hydrolysis were firstly investigated.•The as-prepared flower-like MoS2 spheres exhibited excellent catalytic activity.•Mg-10 wt% MoS2 (as-prepared) composite released 90.4% H2 in 1 min at room temperature.•Available hydrogen generator based on Mg hydrolysis reaction was presented.In this work, flower-like MoS2 spheres are synthesized via a hydrothermal method and the catalytic activity of the as-prepared and bulk MoS2 on hydrolysis of Mg is systematically investigated for the first time. The Mg-MoS2 composites are prepared by ball milling and the hydrogen generation performances of the composites are investigated in 3.5% NaCl solution. The experimental results suggest that the as-prepared MoS2 exhibits better catalytic effect on hydrolysis of Mg compared to bulk MoS2. In particular, Mg-10 wt% MoS2 (as-prepared) composite milled for 1 h shows the best hydrogen generation properties and releases 90.4% of theoretical hydrogen generation capacity within 1 min at room temperature. The excellent catalytic effect of as-prepared MoS2 may be attributed to the following aspects: three-dimensional flower-like MoS2 architectures improve its dispersibility on Mg particles; make the composite more reactive; hamper the generated Mg(OH)2 from adhering to the surface of Mg; and increase the galvanic corrosion of Mg. In addition, a hydrogen generator based on the hydrolysis reaction of Mg-0.2 wt% MoS2 composite is manufactured and it can supply a maximum hydrogen flow rate of 2.5 L/min. The findings here demonstrate the as-prepared flower-like MoS2 can be a promising catalyst for hydrogen generation from Mg.

•Using the hydrolysis by-product as raw material to regenerate NaBH4.•H atom in the coordinate water can be used to compensate H from MgH2.•Obtaining NaBH4 yield (∼90%) with low cost.•Achieving hydrolysis capacity of 6.75 wt % H2.Sodium borohydride (NaBH4) hydrolysis is a promising approach for hydrogen generation, but it is limited by high costs, low efficiency of recycling the by-product, and a lack of effective gravimetric storage methods. Here we demonstrate the regeneration of NaBH4 by ball milling the by-product, NaBO2·2H2O or NaBO2·4H2O, with MgH2 at room temperature and atmospheric pressure without any further post-treatment. Record yields of NaBH4 at 90.0% for NaBO2·2H2O and 88.3% for NaBO2·4H2O are achieved. This process also produces hydrogen from the splitting of coordinate water in hydrated sodium metaborate. This compensates the need for extra hydrogen for generating MgH2. Accordingly, we conclude that our unique approach realizes an efficient and cost-effective closed loop system for hydrogen production and storage.

•(Zr0.7Ti0.3)1.04Fe1.8V0.2 alloy is optimized to have the best overall properties.•(Zr0.7Ti0.3)1.04Fe1.8V0.2 alloy shows no obvious capacity loss after 200 cycles.•A hybrid hydrogen storage system based on (Zr0.7Ti0.3)1.04Fe1.8V0.2 is proposed.•ZrTiFeV alloy is a potential candidate for high pressure MH tank of fuel cell.The combination of unstable hydrogen storage materials with a high pressure tank provides a potential solution to on-board hydrogen storage system for fuel cell vehicles. However, none of the available solid-state materials can fulfill all the requirements. In this work, ZrFeV-based alloys were systematically investigated for the possible use in such kind of hybrid storage devices.Among these alloys studied here, the composition (Zr0.7Ti0.3)1.04Fe1.8V0.2 shows the best overall properties with a reversible hydrogen capacity of 1.51 wt%, and a hydrogen desorption pressure of 11.2 atm at 0 °C. Besides, this alloy also shows excellent stability without obvious capacity loss even after 200 hydrogen absorption/desorption cycles. Calculated results show that the gravimetric density of the hybrid storage system combining a 35 MPa high pressure tank with (Zr0.7Ti0.3)1.04Fe1.8V0.2 alloy is 1.95 wt% when the volumetric density reaches 40 kg/m3.

•New dual-phase TiAL-based intermetallic alloy Ti–40Al–10Fe was developed on the basis of Ti–48Al–10Nb to reduce fabrication cost without losing strengthening.•Two types of gamma-TiAl precipitates including round-shaped and polygon-shaped variants were observed to occur in TiAl(2)Fe matrix.•A detailed investigation to the crystallographic features of gamma-TiAl precipitate in TiAl(2)Fe matrix, including orientation relationship, habit plane, side facets, growth direction and interfacial dislocation, were carried out with TEM method.•Crystallographic features of the polygon-shaped gamma-TiAl precipitate were rationally interpreted by using invariant deformation element model for diffusional phase transformations.Based on TiAl alloys bearing high levels of Nb, which are prospective high-temperature intermetallics, a new dual-phase alloy (Ti–40Al–10Fe (at%)) with precipitate growth direction close to the slipping plane normal of the matrix was developed. Transmission electron microscopy revealed that the annealed alloy was composed of equiaxed grains of τ2-TiAl2Fe and γ-TiAl phases. Aging treatment at 1000 °C produced polygon-shaped γ-TiAl precipitate from the τ2-TiAl2Fe matrix. The precipitation reaction of the face-centered cubic structure of τ2-TiAl2Fe into the ordered face-centered tetragonal structure of γ-TiAl phase was systematically investigated in terms of crystallographic features, including mutual orientation relationship, growth direction, habit plane, side facets, and interfacial dislocation structure. The observed growth direction <973> was close to the normal of the slip plane {111}, with a discrepancy angle of ∼20°. Thus, the observed two-phase microstructure might significantly improve strengthening. It could also be quantitatively controlled by selection of precipitate and matrix with phase structures and lattice parameters that meet a certain requirement.The gamma-TiAl precipitate in TiAl(2)Fe matrix, including orientation relationship, habit plane(6–56), side facet (115), growth direction [97-3] and interfacial dislocation, were carried out with TEM method.

A new complex system, Zr(BH4)4·8NH3–nNH3BH3 (n = 2, 3, 4, 5), was prepared via ball milling of Zr(BH4)4·8NH3 and NH3BH3 (AB). The combination strategy effectively suppressed ammonia release and reduced the dehydrogenation temperature when compared to the individual compounds. In the optimized composition, Zr(BH4)4·8NH3–4AB, the hydrogen purity was improved to 96.1 mol% and 7.0 wt% of hydrogen was released at 100 °C. These remarkable improvements are attributed to the interaction between AB and the NH3 group in Zr(BH4)4·8NH3, which enables a more active interaction of Hδ+⋯−δH. These advanced dehydrogenation properties suggest that Zr(BH4)4·8NH3–4AB is a promising candidate for potential hydrogen storage applications.

A comparative study of Mg5.7In0.3Ag and Mg6Ag alloys was conducted to reveal the effects of indium (In) solid solutions on the hydrogen storage properties of Mg-based alloys. Different from the Mg6Ag alloy, the as-cast Mg5.7In0.3Ag alloy was composed of a Mg(In) solid solution and Mg3Ag. However, an initial hydrogen absorption/desorption treatment (i.e., activation) propelled the In atoms in Mg(In) toward Mg3Ag, forming (Mg, In)3Ag in the activated sample. This transformation involving the dissolution of In atoms from Mg into solid Mg3Ag not only greatly improved the thermodynamics of hydrogen desorption but also enhanced its catalytic effect on hydrogen desorption from additional MgH2. The (Mg, In)3Ag–H2 system exhibited altered thermodynamics, as its enthalpy change of the hydrogen desorption was 62.6 kJ mol−1 H2. Moreover, the activation energy of the hydrogen desorption from the Mg5.7In0.3Ag sample was lowered to 78.2 kJ mol−1.

A new metal borohydride ammoniate (MBA), Zr(BH4)4·8NH3, was synthesized via ammoniation of the Zr(BH4)4 crystal. Zr(BH4)4·8NH3 has a distinctive structure and the highest coordination number of NH3 groups among all the known MBAs. This compound could quickly dehydrogenate at 130 °C, enabling it a potential hydrogen storage material.

•A high-Sm, Pr/Nd-free, and low-Co La0.95Sm0.66Mg0.40Ni6.25Al0.42Co0.32 alloy was prepared.•This alloy showed a high discharge capacity (227.0 mAh/g at 5C).•This alloy exhibited an excellent cyclic stability (80% after 239 cycles).A high-Sm, Pr/Nd-free, and low-Co La0.95Sm0.66Mg0.40Ni6.25Al0.42Co0.32 alloy is reported as an A2B7-type electrode for Ni/MH batteries. The structural characteristics and electrochemical properties of this alloy have been investigated. La0.95Sm0.66Mg0.40Ni6.25Al0.42Co0.32 is composed of La2Ni7 and LaNi5 phases, and shows high discharge capacity and excellent cyclic property. The discharge capacity can reach 311.8 mAh/g and 227.0 mAh/g at large discharge currents of 2C and 5C, respectively, and 80% of the capacity is retained after 239 cycles at 1C.

•The addition of NH4Cl significantly increases the hydrolysis rate of MgH2 and reduces the activation energy.•The hydrolysis mechanisms of MgH2 in pure water and NH4Cl solution are suggested.•The activation energy for hydrolysis of MgH2 in water was determined to be 58.058 kJ/mol.•The activation energy decreased to 50.858 kJ/mol, 30.373 kJ/mol for hydrolysis of MgH2 in 0.5 and 4.5 wt% NH4Cl solution.•MgH2-4.5 wt% NH4Cl system produced 1310 mL g−1 hydrogen in 5 min, and 1660 mL g−1 hydrogen in 30 min at 60 °C.Apparent activation energies of MgH2 hydrolysis in deionized water were deduced for the first time being 58.06 kJ/mol. This paper also reports the mechanisms of MgH2 hydrolysis and the effects of NH4Cl on the kinetics of magnesium hydride hydrolysis. Experimental results show that hydrogen generation via MgH2 hydrolysis exhibited the highest rates in 4.50 wt% NH4Cl solution. This is because addition of NH4Cl could effectively decrease the compactness of magnesium hydroxide. It is also found that addition of NH4Cl could effectively enhance the hydrolysis kinetics and lead to a reduction of the apparent activation energy of MgH2 hydrolysis. The apparent activation energies of MgH2 hydrolysis decreased from 58.06 kJ/mol in deionized water to 50.86 and 30.37 kJ/mol in 0.5 and 4.5 wt% NH4Cl solutions, respectively. MgH2-4.5 wt% NH4Cl system showed the fastest hydrolysis rate, producing 1310 mL g−1 hydrogen in 5 min, 1604 mL g−1 hydrogen in 10 min, and 1660 mL g−1 hydrogen in 30 min at 60 °C. The results reveal that NH4Cl may be a promising reagent for promoting the hydrolysis of MgH2 for hydrogen generation systems, which demonstrated a new method to improve the hydrolysis of MgH2.

•LiBH4 is amorphous after modified with PMMA.•Dehydrogenation temperature of LiBH4 decreases by 120 °C after modifying with PMMA.•The LiBH4@PMMA composite releases 10 wt.% hydrogen at 360 °C within 1 h.•CO group of PMMA weakens the BH bonds to lower dehydrogenation temperature.We investigated the dehydrogenation properties and mechanism of Poly(methyl methacrylate) (PMMA) confined LiBH4. Thermal stability of LiBH4 was reduced by PMMA, with a decrease in dehydrogenation temperature by 120 °C. At 360 °C, the composite showed fast dehydrogenation kinetics with 10 wt.% of hydrogen released within 1 h. The improved dehydrogenation performance was mainly attributed to the reaction between LiBH4 and PMMA forming Li3BO3 as a final product. Furthermore, the presence of electrostatic interaction between B atom of LiBH4 and O atom in the carbonyl group of PMMA may weaken the BH bonding of [BH4]− and lower the hydrogen desorption temperature.

•A fully reversible transformation in Mg–Ga–H system with reduced dehydrogenation enthalpy is realized.•The mechanism of phase transformation in the de/hydrogenation of Mg–Ga alloy is revealed.•The de/hydrogenation process of Mg5Ga2 compound is expressed as: Mg5Ga2 + H2 ↔ 2Mg2Ga + MgH2.Mg-based alloys are viewed as one of the most promising candidates for hydrogen storage; however, high desorption temperature and the sluggish kinetics of MgH2 hinder their practical application. Alloying and changing the reaction pathway are effective methods to solve these issues. As the solid solubility of Ga in Mg is 5 wt% at 573 K, the preparation of a Mg(Ga) solid solution at relatively high temperatures was designed in this paper. The phase transition and hydrogen storage properties of the MgH2 and Mg5Ga2 composite (hereafter referred to as Mg–Ga alloy) were investigated by X-ray diffraction (XRD), pressure–composition-isotherm (PCI) measurements, and differential scanning calorimetry (DSC). The reversible hydrogen storage capacity of Mg–Ga alloy is 5.7 wt% H2. During the dehydrogenation process of Mg–Ga alloy, Mg2Ga reacts with MgH2, initially releasing H2 and forming Mg5Ga2; subsequently, MgH2 decomposes into Mg with further release of H2. The phase transition mechanism of the Mg5Ga2 compound during the dehydrogenation process was also investigated by using in situ XRD analysis. In addition, the dehydrogenation enthalpy and entropy changes, and the apparent activation energy were also calculated.

•New non-stoichiometric Ti–Cr–Mn–Fe alloys are prepared for the hybrid tank.•(Ti0.85Zr0.15)1.1Cr0.925MnFe0.075 has the best overall properties.•The desorption pressure at 0 °C is 10.6 atm.•The reversible gravimetric density remains as a high value of 1.49 wt%.(Ti0.85Zr0.15)1.1Cr1−xMnFex (x = 0, 0.05, 0.075, 0.1, 0.15) alloys with a C14-type Laves structure have been investigated for potential application in hybrid high-pressure metal hydride tanks used for fuel cell vehicles. The effects of the partial substitution of Cr with Fe on the hydrogen storage properties of (Ti0.85Zr0.15)1.1CrMn have been systematically investigated. Results show that the desorption plateau pressure increases with increasing the Fe content in (Ti0.85Zr0.15)1.1Cr1−xMnFex alloys, whereas the hydrogen capacity decreases. Among these alloys, (Ti0.85Zr0.15)1.1Cr0.925MnFe0.075 has the best overall properties, with a hydrogen desorption pressure of 10.6 atm and a reversible capacity of 1.54 wt% at 0 °C under the pressure range between 0.1 atm and 120 atm.

•Mg85In5Al5Ti5 alloy catalyzed with in-situ formed MgF2 was prepared by P-milling.•Reaction mechanism of Mg85In5Al5Ti5 alloy was presented.•Further destabilization of Mg was realized (65.2 kJ/mol H2).•Dual tuning of the thermodynamic and kinetic properties of MgH2 was realized.The dehydrogenation enthalpy change of MgH2 by reversibly forming an Mg0.95In0.05 solid solution offers a new method for tuning the thermodynamics of Mg-based alloys. In order to further lower the stability of MgH2, Al has been introduced into Mg(In) solid solution. At the same time, to solve the problem of sluggish kinetic properties of Mg–In solid–solution systems and to lower the dehydrogenation activation energy, Ti has also been added. It has been demonstrated that the Mg85In5Al5Ti5 alloy synthesized by plasma milling (P-milling) shows both enhanced dehydriding thermodynamics and kinetics. This technique could be used to synthesize Mg(In, Al) ternary solid solution incorporating the Ti catalyst in only one step, making it much more efficient than the two-step method. Compared with Mg-based solid solutions, the addition of Ti and in-situ synthesized MgF2 improved the kinetics and the introduction of In as well as Al imparted enhanced thermodynamics to the Mg85In5Al5Ti5 system. The dehydrogenation enthalpy change and activation energy were lowered to 65.2 kJ/(mol H2) and 125.2 kJ/mol, respectively, for the Mg85In5Al5Ti5 alloy.

•New non-stoichiometric Ti–Cr–Mn based alloys are prepared for the hybrid tank.•(Ti0.85Zr0.15)1.1Cr0.9Mo0.1Mn has the best overall properties.•The desorption pressure at 0 °C is 9.54 atm.•The volumetric density of the hybrid system reaches 40 kg/m3.•The gravimetric density remains as a high value of 2.72 wt%.Ti–Cr–Mn-based alloys with a C14-type Laves structure have been investigated for potential application in hybrid high-pressure metal hydride tanks for fuel cell vehicles. The effects of partial substitution of Ti by Zr, and of Cr by Mo and W, on the hydrogen storage properties of Ti–Cr–Mn-based alloys have been systematically investigated. Among these alloys, (Ti0.85Zr0.15)1.1Cr0.9Mo0.1Mn shows the best overall properties, with a hydrogen desorption pressure and capacity of 9.54 atm and 1.78 wt% at 0 °C. The kinetics and cycling stability are also discussed for on-board hybrid high-pressure metal hydride tank applications. According to calculations, the volumetric H2 density of the hybrid system can reach the Department of Energy (DOE) 2017 target, while its gravimetric density remains at a high value of 2.72 wt% when 28% of the inner volume in a hybrid hydrogen metal hydride tank is filled with this alloy.

An air-stable LiBH4 polymeric composite was successfully prepared by modifying LiBH4 with a gas-barrier polymer matrix, poly(methylmethacrylate) (PMMA). The as-prepared LiBH4@PMMA composite started to dehydrogenate at 53 °C with the first main dehydrogenation peak at 116 °C, and 5.2 wt% of hydrogen released at 162 °C within 1 h.

•H-Mg3CeNi0.1 yielded 1088 mL g−1 (9.71 wt.%) of hydrogen at 298 K.•H-Mg3CeNi0.1 showed superior hydrolysis properties to those of H-Mg3RENi0.1.•Ni served to modify the hydrolysis mechanisms of H-Mg3RE (RE = La, Pr, Nd).•Ni promoted the direct hydrolysis of CeH3 to CeO2 to liberate more hydrogen.•Ni caused the stable Nd2H5 to react with water to increase the hydrogen yield.Nickel has shown to be a good catalyst for improving the hydrolysis performances of hydrogenated Mg3RE (abbreviated as H-Mg3RE, RE = La, Ce, Pr, Nd) through investigating the hydrolysis kinetics and mechanisms of hydrogenated Mg3RENi0.1 (abbreviated as H-Mg3RENi0.1). A material with superior hydrolysis performance, namely H-Mg3CeNi0.1 has been identified, which can generate 276 mL g−1 min−1 hydrogen in the first 1.5 min and achieve a total yield of 1088 mL g−1. Ni served to modify the hydrolysis mechanisms of H-Mg3La, H-Mg3Pr, and H-Mg3Nd to improve their hydrolysis properties. Moreover, Ni has been found to promote the direct hydrolysis of CeH3 to CeO2 to liberate more hydrogen and to render the stable Nd2H5 reactive towards water. Therefore, the studied H-Mg3RE systems all show improved hydrolysis properties after the addition of Ni.

•The Ce2Ni7-type crystal structure of Sm2Co7 compound was confirmed.•β and γ phases were identified as Sm2Co7H2.9 and Sm2Co7H6.4, respectively.•The desorption enthalpy of either β or γ phase was obtained.•The hydrogenation process was a three-dimensional-interface-controlled reaction.•The Sm2Co7 compound showed excellent de/hydrogenation stability.The structural characteristics and hydrogen-storage properties of the Ce2Ni7-type compound Sm2Co7 have been investigated for the first time. This alloy transforms to the β phase and then the γ phase upon hydrogenation. These two phases have been identified as Sm2Co7H2.9 and Sm2Co7H6.4, and their dehydrogenation enthalpies have been measured as 48.5 and 42.0 kJ/mol H2, respectively. Sm2Co7 shows excellent stability without obvious capacity loss after 50 cycles, and its hydrogenation process follows a three-dimensional-interface-controlled reaction at ambient temperature.

•The microstructure evolution of T92 steel after creep were studied systematically.•The spheroidal-shaped of M23C6 is more stable than the rod one during creep.•The coarsening kinetics of Laves phase was notably affected by plastic deformation.Standard tests for creep and rupture strength were carried out on T92 martensitic heat-resistant steel at the temperatures of 600, 650, and 700 °C and stress levels of 46–200 MPa. The creep life of T92 steel was estimated through the Larson–Miller parameter, which was calculated from the aging temperature and aging time. Crystal structures and morphologies of precipitate phases after creep were investigated by scanning electron microscopy and transmission electron microscopy, and the composition was analyzed by energy dispersive X-ray spectrometry. Degeneration processes after creep exposure of the martensitic microstructure, namely, martensitic substructure recovery, as well as coarsening and precipitation of second phases, were also observed.

•H-Mg3La with particle size of [<12] μm yields 7.70 wt.% hydrogen.•The hydrolysis mechanisms of H-Mg3La with different particle sizes are revealed.•Reducing the particle size could improve hydrolysis rate and yield.The effect of particle size on hydrolysis properties of hydrogenated Mg3La was investigated through fixing the grain size of in-situ formed LaH3 and MgH2 from hydrogenated Mg3La. The hydrolysis rate and hydrogen yield were affected by its particle size. The hydrogenated Mg3La with smaller particle size of [<12] μm had a higher hydrolysis yield of 863 ml g−1 (7.70 wt.%) hydrogen. The surface area and defect of samples were increased through reducing the particle size and thus promoted the complete hydrolysis. Reducing the particle size is an effective and simple method to improve hydrolysis properties of magnesium hydrides-based materials.

•The fully hydrogenated Mg3LaH9 yields 7.80 wt.% hydrogen.•The hydrogenation mechanism for Mg3La alloy is revealed.•The hydrogenation degree affects the hydrolysis properties of Mg3LaHx hydrides.•The hydrolysis performance of MgH2 is accelerated significantly by LaH3.•The hydrolysis rate is controllable by adjusting the ratio of LaH3 to MgH2 or Mg.This paper reports the synthesis of Mg3La alloys with different hydrogenation degree through controlling the hydrogen amount introduced and reveals the hydrogenation mechanism. The hydrolysis rate and hydrogen yield of Mg3La hydride could be controllable through adjusting the ratio of LaH3 to Mg or MgH2. The fully hydrogenated Mg3La alloy can generate 873.24 ml g−1 in 66 min (7.80 wt.%). The results show that the hydrolysis performance of MgH2 in Mg3La hydrides could be significantly accelerated by LaH3 while that of Mg was affected limitedly by LaH3.

•Amorphous carbon coated ZnGeP2 powder with P-C bond is synthesized for both lithium ion batteries and sodium ion batteries.•The ZnGeP2/C composite has not been reported in use of lithium ion batteries and sodium ion batteries•The ZnGeP2/C composite demonstrates excellent electrochemical performance for both lithium ion and sodium ion batteries.•The raw materials Zn, Ge and P powders are abundant and the method is high yield, low-cost and environmentally friendly.A novel ZnGeP2/C composite was synthesized by simple ball milling and used as an anode for both lithium-ion and sodium-ion batteries. Due to the synergistic effect of amorphous carbon, PC bond and intermediate charge/discharge products, the composite anode delivers a high reversible capacity of 807 mA h g− 1 at 0.2 A g− 1 after 100 cycles for lithium-ion batteries and 584 mA h g− 1 at 0.1 A g− 1 after 50 cycles for sodium-ion batteries.

The hydrolysis of NaBH4 offers significant advantages for hydrogen storage in fuel cells, whereby suffers from the irreversibility. Thus, a simple and low cost method for NaBH4 regeneration from its hydrolysis byproduct is crucial. Herein, we describe a single step method for NaBH4 regeneration, which combines both hydrogen production and storage in the one step. In the process, a mixture of magnesium silicide and dihydrate sodium metaborate is reacted via ball milling under ambient conditions without the requirements of additional hydrogen sources. The hydrogen only comes from the splitting of H2O in the NaBO2·2H2O that is a direct byproduct of NaBH4 hydrolysis. The purified product demonstrates the same physicochemical properties as commercial NaBH4. Yields for NaBH4 regeneration approaching 80% are achieved using this method. Mechanism study indicates that the high yield is likely to be beneficial from the formation of the Mg-O-Si-H conjugated structure. NaBH4 regeneration using this process demonstrates a 30-fold reduction in cost over a previous study that used MgH2 as the reduction agent.Download high-res image (142KB)Download full-size image

A new complex system, Zr(BH4)4·8NH3–nNH3BH3 (n = 2, 3, 4, 5), was prepared via ball milling of Zr(BH4)4·8NH3 and NH3BH3 (AB). The combination strategy effectively suppressed ammonia release and reduced the dehydrogenation temperature when compared to the individual compounds. In the optimized composition, Zr(BH4)4·8NH3–4AB, the hydrogen purity was improved to 96.1 mol% and 7.0 wt% of hydrogen was released at 100 °C. These remarkable improvements are attributed to the interaction between AB and the NH3 group in Zr(BH4)4·8NH3, which enables a more active interaction of Hδ+⋯−δH. These advanced dehydrogenation properties suggest that Zr(BH4)4·8NH3–4AB is a promising candidate for potential hydrogen storage applications.

An air-stable LiBH4 polymeric composite was successfully prepared by modifying LiBH4 with a gas-barrier polymer matrix, poly(methylmethacrylate) (PMMA). The as-prepared LiBH4@PMMA composite started to dehydrogenate at 53 °C with the first main dehydrogenation peak at 116 °C, and 5.2 wt% of hydrogen released at 162 °C within 1 h.

A new metal borohydride ammoniate (MBA), Zr(BH4)4·8NH3, was synthesized via ammoniation of the Zr(BH4)4 crystal. Zr(BH4)4·8NH3 has a distinctive structure and the highest coordination number of NH3 groups among all the known MBAs. This compound could quickly dehydrogenate at 130 °C, enabling it a potential hydrogen storage material.

A comparative study of Mg5.7In0.3Ag and Mg6Ag alloys was conducted to reveal the effects of indium (In) solid solutions on the hydrogen storage properties of Mg-based alloys. Different from the Mg6Ag alloy, the as-cast Mg5.7In0.3Ag alloy was composed of a Mg(In) solid solution and Mg3Ag. However, an initial hydrogen absorption/desorption treatment (i.e., activation) propelled the In atoms in Mg(In) toward Mg3Ag, forming (Mg, In)3Ag in the activated sample. This transformation involving the dissolution of In atoms from Mg into solid Mg3Ag not only greatly improved the thermodynamics of hydrogen desorption but also enhanced its catalytic effect on hydrogen desorption from additional MgH2. The (Mg, In)3Ag–H2 system exhibited altered thermodynamics, as its enthalpy change of the hydrogen desorption was 62.6 kJ mol−1 H2. Moreover, the activation energy of the hydrogen desorption from the Mg5.7In0.3Ag sample was lowered to 78.2 kJ mol−1.

Reversible hydrogen storage has been found in transition metal alanates, Y(AlH4)3, for the first time. An amount of 3.4 wt% H2 can be released at 140 °C from the first dehydrogenation step of Y(AlH4)3, and 75% of it is reversible at 145 °C and 100 bar H2, which holds promise for low-temperature applications.

Hydrogen generation is one of the enabling technologies for realization of hydrogen economy. In this study, we developed a high-performance hydrogen generation system using the transition metal Mo and its compounds (MoS2, MoO2, and MoO3) for catalyzing the hydrolysis of Mg composites in seawater. These Mg-based composites for the hydrolysis process were synthesized through a simple planetary ball mill technique. The results demonstrate that small amounts of added MoS2 could significantly accelerate and enhance the hydrolysis reaction of Mg in seawater. In particular, the Mg–10 wt% MoS2 composite releases 838 mL g−1 hydrogen in 10 min (about 89.8% of the theoretical hydrogen generation yield), and the recycled catalysts exhibit high cycle stability, which is the most significant achievement in this study. In addition, Mo, MoO2, and MoO3 also showed similar enhancement in the hydrolysis reaction of Mg. The activation energies for the hydrolysis of Mg decreased from 63.9 kJ mol−1 to 27.6 kJ mol−1, 20.4 kJ mol−1, 14.3 kJ mol−1, and 12.1 kJ mol−1 on introducing Mo, MoS2, MoO2, and MoO3, respectively. The attractive hydrolysis performance of the composites of Mg milled with Mo and its compounds in seawater may shed light on future developments of hydrogen generation technologies.