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Abstract: On the synthesis of nano-structural hydrogenated graphite by ball-milling under H2 atmosphere, iron contamination was mingled from steel balls during ball-milling. It is clarified by spectroscopic measurements that the mingled iron formed a non-stoichiometric iron–carbon (Fe–C) compound. The Fe–C phase was transformed to a well-ordered phase with H2 desorption at 450°C, suggesting that the hydrogen atoms were anomalously trapped at the Fe–C phase. With respect to hydrogen absorbing properties, the mingled iron enhanced the hydrogen capacity by about 50% compared with iron free hydrogenated graphite, where H/Fe was about 13mass%. Therefore, if the hydrogen absorption site originated in the Fe–C phase could be synthesized independently, it should be recognized as a promising hydrogen storage system. [ABSTRACT FROM AUTHOR]

Abstract: Thermal analyses of the mixture of MgH2 and LiBH4 doped with TiCl3, and each element MgH2 or LiBH4 doped with TiCl3 were performed under an inert gas flow and 0.5MPa H2-gas conditions. It was indicated that the hydrogen desorption reaction of MgH2 +2LiBH4 to MgB2 +2LiH+4H2 phases proceeded at temperature above 400°C under 0.5MPa hydrogen, whereas, under an inert gas atmosphere, the reaction of the same mixture was transformed into Mg+2B+2LiH+4H2 phases in a temperature range from 350 to 430°C. Before these reactions, the dehydrogenation of MgH2 and the melting of LiBH4 took place under both hydrogen and the inert gas atmospheres with increasing temperature. In addition, the molten LiBH4 did not decompose into LiH, B and H2 below 450°C under 1MPa H2, while the LiBH4 decomposed even below 450°C under an inert gas atmosphere. From these results, it is deduced that the reaction producing MgB2 is a solid–liquid reaction between solid Mg and liquid LiBH4 above 400°C without decomposition of molten LiBH4 under a hydrogen atmosphere, while MgH2 dehydrogenate. A characteristic solid–liquid reaction is realized under a hydrogen atmosphere for proceeding of the MgB2 producing reaction in this system. [Copyright &y& Elsevier]

Abstract: The hydrogen absorption kinetics of magnesium hydride (MgH2) composite doped with 1mol% Nb2O5 prepared by ball milling was examined under various temperatures and pressures. The composite after dehydrogenation at 200°C absorbs gaseous hydrogen of ∼4.5mass% within 15s even at room temperature under 1.0MPa hydrogen pressure or at 0°C under 3.0MPa, and finally their capacities reach up to 5mass%. At 150 and 250°C, a large amount of hydrogen gas of more than 5.0mass% is absorbed within 30s and their capacity reach up to 5.7mass% under 1.0MPa. Interestingly, the absorption kinetics of the catalyzed Mg shows two unusual behaviors in the initial reaction stage of the time scale within 30s. One is that the kinetics decreases with increase in the temperature from 150 to 250°C under any pressures (0.2, 1.0 and 3.0MPa). The other is that the amount of hydrogen absorption drastically increases with increase in the initial pressure from 1.0 to 3.0MPa at 0°C or from 0.2 to 1.0MPa at room temperature (∼20°C). These behaviors may be explained by taking into account heat generation of Mg due to fast hydrogen uptake in such a short time. [Copyright &y& Elsevier]

Abstract: We synthesized BNnanoCH x by ball-milling hBN under methane atmosphere. This BNnanoCH x product itself desorbed not only hydrogen but also hydrocarbons in a wide temperature range from 300 to 900°C. Moreover, Fourier transform infrared (FT-IR) spectroscopy for BNnanoCH x indicated the existence of the C–H bonding in the material. On the analogy of the CnanoH x –LiH composite reported before, we prepared the composite of BNnanoCH x and LiH. This composite successfully desorbed hydrogen around 200°C, in which the emission of the hydrocarbon gases was strongly suppressed. Thermodynamic and structural properties of the composite showed an interaction between the C–H groups and LiH. Thus we found that the BNnanoCH x –LiH composite is a new hydrogen storage material. [Copyright &y& Elsevier]

Abstract: Hydrogen desorption properties of mechanically milled materials composed of nano-structural hydrogenated-graphite (CnanoH x ) and alkali(-earth) metal hydride (MH; M=Na, Mg and Ca) were investigated from the thermodynamic and structural points of view. The hydrogen desorption temperature for all the CnanoH x and MH composites was obviously lower than that of the corresponding each hydride. In addition, the desorption of hydrocarbons from CnanoH x was significantly suppressed by making composite of CnanoH x with MH, even though CnanoH x itself thermally desorbs a considerably large amount of hydrocarbons. These results indicate that an interaction exists between CnanoH x and MH, and hydrogen in both the phases is destabilized by a close contact between polar C–H groups in CnanoH x and the MH solid phase. Moreover, a new type of chemical bonding between the nano-structural carbon (Cnano) and the Li, Ca, or Mg metal atoms may be formed after hydrogen desorption. Thus, the above metal–C–H system would be recognized as a new family of H-storage materials. [Copyright &y& Elsevier]

Abstract: The in-situ XRD measurements on dehydrogenation/rehydrogenation of the Li–Mg–N–H system were performed in this work. The ballmilled mixture of 8LiH and 3Mg(NH2)2 as a hydrogenated phase gradually changed into Li2NH as a dehydrogenated phase during heat-treatment at 200°C in vacuum for 50h. Neither Mg-related phases nor other intermediate phases were recognized in the dehydrogenated phase. With respect to the hydrogenation process, the dehydrogenated state gradually returned to the mixed phase of the LiH and Mg(NH2)2 without appearance of any intermediate phases during heat treatment at 200°C under 5MPa H2 for 37h and during slow cooling down to room temperature through 24h. In the hydrogenation process at 200°C under 1MPa H2, however, the growing up of the LiNH2 and LiH phase was observed in the XRD profiles before the 3Mg(NH2)2 and 8LiH phases were formed as the final hydrogenated state. This indicates that the LiNH2 and LiH phase essentially appears as an intermediate state in the Li–Mg–N–H system composed of 3Mg(NH2)2 and 8LiH. [Copyright &y& Elsevier]

Abstract: Kinetics of hydrogen absorption and desorption reactions was investigated on the MgH2 composite doped with 1mol% Nb2O5 as a catalyst by ballmilling. The composite after dehydrogenation at 200°C absorbed gaseous hydrogen of ∼4.5mass% even at room temperature under lower pressure than 1MPa within 15s and finally its capacity reached more than 5mass%. On the other hand, the catalyzed MgH2 after rehydrogenation desorbed ∼6mass% hydrogen at 160°C under purified He flow, which followed the first order reaction. From the Kissinger plot, the activation energy for hydrogen desorption was estimated to be ∼71kJ/molH2, indicating the product was significantly activated due to the catalytic effect of Nb2O5. [Copyright &y& Elsevier]

Abstract: Isothermal hydrogen absorption properties of the ball milled mixture of 3Mg(NH2)2 and 8LiH after dehydrogenation at 200°C under high vacuum were investigated at two different temperatures of 150 and 200°C. The pressure–composition isotherm (PCT) curve at 200°C revealed a two-plateaus-like behavior, while the PCT curve at 150°C showed a single-plateau-like behavior. The hydrogenated phases were composed of LiH and Mg(NH2)2 under 9MPa at 200°C, while those were observed as mixed phases of LiH and LiNH2 at 150°C without any trace of Mg(NH2)2 in XRD measurements. These results indicate that there are two-step hydrogenation processes corresponding to high and low pressures at 200°C, but the kinetics at 150°C is too slow to proceed with the second hydrogenating step at high pressure region. [Copyright &y& Elsevier]

Abstract: After synthesizing calcium amide (Ca(NH2)2) through the reaction of calcium hydride (CaH2) with ammonia (NH3), the thermal decomposition properties have been examined. The results indicated that Ca(NH2)2 decomposed to calcium imide (CaNH) and NH3 gas with increasing temperature, where the desorption of NH3 started from about 60°C and peaked around 300°C in the thermal desorption mass spectra (TDMS). From the X-ray diffraction profiles, the product after heat treatment up to 350°C was CaNH, but an unknown phase appeared in further heating up to 500°C. Hydrogen (H2) desorption properties of a mixture of Ca(NH2)2 and CaH2 with 1:3 molar ratio were also examined. The H2 gas of 3.5wt.% in total was desorbed with two-peak structure in TDMS. The first peak corresponds to the reaction: Ca(NH2)2 +CaH2 →2CaNH+2H2, and the second one originates from the reaction: CaNH+CaH2 →Ca2NH+H2. Simultaneously performed differential thermal analysis indicated that the former and the latter reactions were, respectively, exothermic and endothermic, so that the H2 desorption corresponding to the first peak in TDMS disappeared after long-time-milling at room temperature. [Copyright &y& Elsevier]

In this work, we clarified the correlation between hydrogen storage and crystallographic properties in nanostructural magnesium hydride MgH2 prepared by mechanical milling under hydrogen gaseous atmosphere. At the early stage within 2 h milling, the amount of desorbed hydrogen decreases ∼16% from 7.3 to 6.1 wt.% and the onset temperature of dehydrogenation decreases by 70 K from 670 K, while both the powder size and the crystallite size in powder decrease with increasing the milling time down to 1 μm and 15 nm, respectively, and the lattice strain of 0.3% is rapidly introduced. At the middle stage with longer milling time than 2 h, however, the crystallite size hardly change, but the lattice strain is once released at 2–5 h milling and again increases for longer milling time than 5 h. On the other hand, the amount of desorbed hydrogen suddenly increases from 2 to 5 h, and again decreases with a little increase of lattice strain during 5–80 h milling. At the final stage, the hydrogen capacity and desorption temperature reach to saturation of, respectively, 6.5 wt.% and 600 K, whereas the crystallite size and lattice strain reach to saturation of ∼7 nm and 0.2%, respectively. The results obtained indicate that the reduction of crystallite size as well as the introduction of lattice strain in MgH2 during milling gives rise to the decrease in hydrogen storage capacity. [Copyright &y& Elsevier]

In this paper, we examined the basic properties in the 1:1 mixture of lithium amide LiNH2 and lithium hydride LiH as a candidate of reversible hydrogen storage materials. The thermal desorption mass spectra of the ball milled mixture without any catalysts indicated that hydrogen H2 is released in the temperature range from 180 to 400 °C while emitting a considerable amount of ammonia NH3. On the other hand, the ball milled mixture containing a small amount of TiCl3 as a catalyst showed the most superior hydrogen storage properties among the 1:1 mixtures with a small amount of catalysts, Ni, Fe, Co metals and TiCl3 (1 mol.%). That is, the product desorbs a large amount of hydrogen (∼5.5 wt.%) in the temperature from 150 to 250 °C under the condition of a heating rate of 5 °C/min, but it does not desorb ammonia at all within our experimental accuracy. In addition, we confirmed that the product shows an excellent cycle retention with an effective hydrogen capacity of more than 5 wt.% and a high reaction rate until at least 3 cycles. [Copyright &y& Elsevier]

Abstract: A lithium-nitrogen-hydrogen (Li-N-H) system has been reported as one of the attractive hydrogen storage systems. So far, it was clarified that some catalysts, especially titanium-based compounds, were significantly effective for improving the hydrogen storage kinetics in the Li-N-H system. In this research, the chemical bonding states of the titanium compounds in the mixture of LiH and LiNH2 were examined by X-ray absorption spectroscopy (XAS) as the characterization of the catalysts. The results of X-ray absorption near-edge structure (XANES) indicated that the Ti atoms in the titanium compounds, which revealed the catalytic effect on the hydrogen desorption (H-desorption) properties, had a common electronic (chemical bonding) state. [Copyright &y& Elsevier]

Abstract: A mixture of LiNH2 and LiH is one of the complex hydride systems for hydrogen storage, and desorbs H2 with a small amount of NH3 as a contaminant. NH3 impurity in the H2 stream for polymer electrolyte membrane fuel cells causes poisoning of the cells, which is severe problem for the application. In this work, NH3 and H2 partial pressures in the desorbed gas from LiH+LiNH2 +1mol% TiCl3 in a closed system were quantitatively estimated by infrared spectroscopy and gas chromatography analysis. H2 and NH3 were significantly desorbed in the high-temperature range of 300–400°C, and the NH3/H2 ratio was on the order of 0.1% in this temperature range. [Copyright &y& Elsevier]

Anti-oxidation properties of Cr substitution were investigated by comparing TiFe and TiFe 0.9 Cr 0.1. Kinetic measurements reveal that the degradation rate of TiFe 0.9 Cr 0.1 is slower than that of TiFe, indicating that Cr substitution drastically enhances the anti-oxidation properties of the mother alloy TiFe. In order to understand the mechanism of this effect, X-ray photoelectron spectroscopy (XPS) was used to identify the surface chemical state of these alloys, which indicates that Cr plays quite an important role in the suppression of surface oxidation. It is clarified that the deactivation of TiFe is caused by the oxidation of Ti on the surface and, as a result, the obstruction of hydrogen penetration. On the contrary, with the substitution of Cr for Fe in TiFe 0.9 Cr 0.1 , the Ti oxidation becomes more difficult even though the Cr was totally oxidized, which makes it easier to keep the initial activated state of hydrogenation (Ti with a low oxidation state). It also further demonstrated that Cr acts as a sacrificial element, undergoing complete oxidation to protect Ti from oxidation, and assists in keeping metallic Ti0, which is crucial for maintaining the hydrogen absorption kinetics. Therefore, the Cr substitution for Fe significantly improves the anti-oxidation properties of TiFe-based alloys. • Cr substitution improves the anti-oxidation properties of TiFe alloy. • The oxide layer composition changed when Fe was substituted by Cr in TiFe alloy. • Cr acted as a sacrificial element to prevent the oxidation of Ti. • Ti oxidation is the primary cause of the deactivation of TiFe alloy. [ABSTRACT FROM AUTHOR]

Abstract: Three carbon materials were prepared for the synthesis of Li–C compounds, such as Li intercalated graphite. The materials were as-received high purity polycrystalline graphite (G), graphite milled under a hydrogen atmosphere (HG), and graphite milled an argon atmosphere (AG). With respect to the difference for them, HG preserved a better crystalline structure than AG. Each material was milled with Li, where the products are denoted as Li-G, Li-HG, and Li-AG. In XRD patterns of Li-G and Li-HG, the peaks corresponding to LiC6 and LiC12 were revealed, while no peaks were observed in the case of Li-AG. However, the formation of lithium carbide Li2C2 was suggested for Li-AG by a thermal analysis under an inert gas. After the hydrogenation, LiH was formed for all the compounds, and graphite was recovered for Li-G and Li-HG. Each hydrogenated compound desorbed H2 with different profile by heating up to 500°C. As a reaction product, Li2C2 was formed for the hydrogenated Li-HG and Li-AG. In the case of the hydrogenated Li-G with better crystalline structure, Li intercalated graphite were formed after the dehydrogenation. Therefore, it is concluded that the hydrogen absorption and desorption process of Li intercalated graphite was different from those of Li2C2. [ABSTRACT FROM AUTHOR]

Abstract: The microstructures of MgH2 catalyzed with Ni nano-particle or Nb2O5 mesoporous powders are examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. For MgH2 catalyzed with Ni, the Ni particles with the diameter smaller than 1μm were detected on the MgH2 particles with the diameter smaller than 5μm by the back scattering electron (BSE) microscopy. In details, the TEM micrograph indicates that the Ni particles distribute ∼20nm in diameter on MgH2 uniformly, which was the same size as the additive doped in MgH2 before milling. On the other hand, for MgH2 catalyzed with Nb2O5, the additive particles could not be found anywhere in the BSE image. Even in the TEM micrograph by much larger magnification than the SEM micrograph, the particles corresponding to the additive cannot be observed at all. Furthermore, an energy dispersive X-ray (EDX) analysis in spots with a diameter of 20nm indicated that the existing ratio of Mg to Nb was evaluated to 98:2, being the same as the starting ratio before milling. Therefore, the metal oxide Nb2O5 becomes extremely small particle that could not be observed by the present work after milling compared to metal Ninano. [Copyright &y& Elsevier]

Abstract: Hydrogen storage properties of two ball-milled composites of Ca(NH2)2 +2LiH and CaH2 +2LiNH2 were investigated as a series of searching studies of high performance hydrogen storage materials. About 4.5mass% hydrogen is desorbed from about 100°C and the thermal desorption profiles show a peak around 200 and 220°C for the composites of CaH2 +2LiNH2 and Ca(NH2)2 +2LiH, respectively, under a helium flow at 5°C/min heating rate without any NH3 emission within our experimental accuracy. The powder X-ray diffraction and infrared absorption spectroscopy indicated that the dehydrogenated states of both composites form “an unknown imide phase” after heating up to 400°C, while the dehydrogenated states after heating up to 200°C in vacuum are the mixed phases of Li2NH and CaNH. The rehydrogenated state for the ball-milled composite of CaH2 +2LiNH2 is transformed into the composite of Ca(NH2)2 and 2LiH by repeating the dehydrogenation and rehydrogenation cycles at 180–200°C. [Copyright &y& Elsevier]

Abstract: We successfully established a method to synthesize the Li–Mg–N–H hydrogen storage system composed of Mg(NH2)2 and LiH from Mg and LiNH2 as starting materials. First of all, Mg and Li2NH were homogeneously mixed by ball-milling for 2h under 1MPa argon atmosphere. After that, the mixture was heat-treated at 250°C for 16h under vacuum condition to be transformed into Mg3N2 and Li2NH. Target materials, Mg(NH2)2 and LiH, were synthesized by a further heat-treatment for Mg3N2 and Li2NH at 200°C under 10MPa hydrogen atmosphere for 12h. The phases in the sample at each processing stage were examined by X-ray diffraction (XRD) and Fourier transformation infrared absorption measurements and confirmed to be the expected ones. From experimental results of a thermal desorption mass spectroscopy, the final hydrogenated sample indicated that ∼7mass% hydrogen was desorbed starting from about 150°C and peaked around 230°C under helium flow condition at 5°C/min heating rate without ammonia emission in our experimental accuracy. [Copyright &y& Elsevier]

Iron Phosphide (Fe 2 P) particles embedded within in-situ generated tubular carbon structures uniformly doped with nitrogen heteroatoms (Fe 2 P @ NC) have been investigated as an anode in all-solid-state lithium-ion batteries (ASSLIBs). The designed morphology offered a number of suitable features, such as high conductivity, robust framework, and abundant redox active sites for augmenting overall battery performance. As anode, Fe 2 P @ NC has provided a high lithiation/delithiation capacity of 1214.8 mA h/g /1367.01 mA h/g at a current density of 66.6 mA/g (100 μA) with a high coulombic efficiency (>100%). Further, Fe 2 P @ NC also demonstrated an excellent rate performance and moderate structural stability during cycling. The charge storing mechanism for Fe 2 P @ NC investigated via ex-situ X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) studies indicates irreversible conversion of Fe 2 P → Li 3 P & Fe in the initial cycle and reversible Li 3 P ↔ LiP reaction in subsequent cycles. Analysis of reaction kinetics for Fe 2 P @ NC nanocomposite is carried out using CV measurements at different scan rates. This study explores the possibility of MOF-derived iron-phosphide-based composite material as a high-performance anode for ASSLIBs. [Display omitted] • MOF-derived iron phosphide composite (Fe 2 P @ NC) is utilized in all-solid-state batteries. • The charge-storage mechanism has been established using ex-situ XRD and XPS profiles. • Fe 2 P @ NC could deliver a high initial discharging capacity of 1214.8 mAh g−1 at a current density of 66.6 mA/g. • Reaction-controlled and diffusive contributions in total current have been evaluated. • The cyclic performance of the Fe 2 P @ NCF-based electrode has been revealed. [ABSTRACT FROM AUTHOR]

Solid-state hydrogen storage has emerged as an efficient and reliable technique to commercialize hydrogen energy on a large scale. Magnesium hydride (MgH 2), amongst other materials, shows excellent hydrogen storage capability. However, it suffers from setbacks like sluggish kinetics and high thermodynamic stability. Several studies have shown that doping with suitable materials is an effective method to improve the sorption kinetics. Current work is concerned with doping of MgH 2 with perovskite-type ternary metal oxide NaNbO 3 at 5,10 & 15 wt% doping concentration via ball milling and study of its sorption properties. Thermal desorption mass spectra (TDMS) with thermogravimetry (TG) and Differential scanning calorimetry (DSC) validate the optimum doping concentration to be 10 wt% NaNbO 3 in MgH 2. According to the isothermal hydrogenation plots, 10 wt% catalyzed sample was capable of absorbing 5.29 wt% hydrogen in just 4.2 min at 150ºC which by far outperforms the 2 h milled MgH 2 sample which under the same set of conditions absorbs only 0.67 wt% H 2. The catalyst starts affecting the absorption rate right from the room temperature whereas the milled sample has minimal absorption throughout the experiment. At room temperature, the average rate of absorption grows by factor 7 which is staggeringly high. The Kissinger analysis reveals activation energy for hydrogen release as 73.12 kJ/mol for 10 wt% doped NaNbO 3 -MgH 2 system while 137.13 kJ/mol for as milled MgH 2. The pressure-temperature isotherm (PCI) at four different temperatures gives a quantitative measure of the thermodynamic stability of the system. To fully comprehend the catalytic process, XRD, SEM, and XPS analysis were conducted after each stage of experiment. XPS suggested possible reduction of Nb valance state from + 5 to + 2 due to surface reduction reaction which further accelerated the sorption kinetics due to the electron transfer process. [Display omitted] • NaNbO 3 is utilized as a catalyst to enhance the sorption kinetics of MgH 2. • The doping of 10 wt% NaNbO 3 reduces the desorption temperature of dehydrogenation. • At room temperature, catalyzed MgH 2 absorbs hydrogen at a rate that is seven times faster than milled MgH 2. • The in-situ reduction of NaNbO 3 causes MgH 2 to dehydrogenate more quickly. [ABSTRACT FROM AUTHOR]

In this work, systematic research on catalytic properties of group 4–6 element oxides, which are TiO 2 , ZrO 2 , HfO 2 , V 2 O 5 , Ta 2 O 5 , CrO 3 , MoO 3 , and WO 3 , for magnesium hydride (MgH 2), were carried out to understand important factors for the formation of catalytic active state. Each oxide is dispersed on the MgH 2 surface by the ball-milling under the same conditions. The hydrogen desorption properties are investigated, and the oxides on the MgH 2 are characterized by structural and spectroscopic analyses. Although all the oxides show catalysis for the hydrogen desorption process, TiO 2 , V 2 O 5 , ZrO 2 , and CrO 3 particularly reveals higher catalytic activity, resulting in the hydrogen desorption around 200 °C. For TiO 2 , V 2 O 5 , CrO 3 , ZrO 2 , and MoO 3 , a highly dispersed state of the oxides on Mg is found, suggesting that the catalysis is related to the dispersion process. Among the above oxides, only MoO 3 does not show the higher catalysis even though it is highly dispersed on Mg. To know the other control factors of the catalysis, the chemical state of transition metals is investigated by X-ray photoelectron spectroscopy. As a result, it is clarified that the high catalytic activity is obtained in case the transition metals form multi oxide state especially including 2 + and 3 + oxidation states. From the above experimental facts, it is expected that the reduction and dispersion of oxides simultaneously proceed during the ball-milling process, and the oxides with intermediate oxidation states shows the high catalysis for the Mg system. • Catalysis of group 4–6 element oxides for the H 2 desorption and absorption reactions of MgH 2 is systematically investigated. • Oxides with high catalytic activity possesses highly dispersed state on the Mg surface, which increases frequency factor. • Oxides with high catalytic activity possesses multi oxidation state including 2 + and/or 3 + , which decreases activation energy. • Dispersion and reduction of oxides simultaneously proceed during sample preparation process by ball-milling method. [ABSTRACT FROM AUTHOR]

Hydrogen desorption properties of α-AlH 3 doped with Nb species (Nb, Nb 2 O 5 and NbF 5 ) were investigated. Doping Nb species improved the desorption properties of AlH 3 . In particular, 1 mol% NbF 5 -doped AlH 3 showed the lowest onset desorption temperature at 60 °C. Compared with Nb- or Nb 2 O 5 -doped AlH 3 , the fine distribution of dopant was successfully achieved in NbF 5 -doped AlH 3 . The apparent activation energy for hydrogen desorption of AlH 3 was slightly decreased with the dopant of NbF 5 . The improvement of desorption properties might be due to the finely dispersed Nb and/or AlF 3 , which are formed by the reaction between NbF 5 and AlH 3 (surface Al 2 O 3 ). [ABSTRACT FROM AUTHOR]

Lithium metatitanate (Li 2 TiO 3 ) doped magnesium hydride (MgH 2 ) has been investigated in this paper. Desorption properties of the sample with catalyst are compared to the pure MgH 2 . Particularly, MgH 2 doped with 5 mol % Li 2 TiO 3 started to desorb hydrogen at 170 °C with a peak temperature at 211 °C, which is 100 °C and 80 °C lower than that of the as-milled MgH 2 . The reversibility and cyclability of sample with catalyst have also been investigated. Compared with the raw material, the desorption activation energy was reduced from 113 kJ/mol to 84 kJ/mol. Furthermore, the catalytic mechanism was discussed according to the experimental results. [ABSTRACT FROM AUTHOR]

The corrosion of carbide/nitride/oxide(C/N/O)-based reactor materials were investigated to solve the corrosion problems in sodium redox reactions for thermochemical hydrogen production in this work. Various types of carbides, nitrides, and oxides were used as the potential materials of reaction containers for the sodium redox cycle to expect strong corrosion resistance. Comparison of corrosion of materials was performed by heat treatment with Na 2 O at 500 °C and corrosive phases were identified by X-ray diffraction. All the carbides materials showed the low corrosion resistance, while AlN among all the nitrides and Al 2 O 3 among all the oxides were proved to possess high corrosion resistance with a very less corrosive phase from XRD results and non-discoloration of the test plate. The order of corrosion resistance of various materials was determined from the width of the corrosive layer observed by SEM and from the evaluation of Gibbs energy corresponding to the corrosion reaction from the thermodynamic point of view. The order of corrosion resistance was found to be AlN > Al 2 O 3 > ZrO 2 > TiO 2. As a result, AlN was the most corrosive-resistant material according to SEM, XRD and EDS methods. • Sodium redox reactions is hindered by unexpected corrosion reaction. • Various ceramics materials are investigated by heating experiment with Na 2 O at 500 °C. • Corrosive layers were observed by SEM/EDS to check the degree of corrosion. • The corrosion resistance order of oxides was determined as Al 2 O 3 > ZrO 2 > TiO 2. • AlN was recognized to be the robust corrosion resistance among all the samples. [ABSTRACT FROM AUTHOR]

Recently KSiH 3 has been proposed as an attractive contender toward hydrogen storage media, owing to its high storage capacity i.e. 4.3 wt% within a good P-T window. The high activation energy for desorption allows KSiH 3 to desorb hydrogen slowly only at 200 °C in more than 5 h. Moreover, the efforts to improve the kinetics by means of milling with carbon powder disproportionate KSiH 3 into KH, Si and K–Si intermetallic phases. A number of known nano-metals viz. Ni, Co, and Nb are attempted in order to improve the sorption properties of KSiH 3 . Nano-Ni is found to be most effective catalyst with the lowest value of activation energy 106 kJ mol −1 in comparison to 142 kJ mol −1 for as annealed KSi sample. [ABSTRACT FROM AUTHOR]

Abstract: Metal aluminum amides M[Al(NH2)4] x (M =K, Mg, and Ca; x =1 and 2) were synthesized along with previously reported LiAl(NH2)4 and NaAl(NH2)4 by ball milling technique under liquid NH3. The profiles of synchrotron radiation X-ray diffraction suggest that KAl(NH2)4, Mg[Al(NH2)4]2 and Ca[Al(NH2)4]2 have been indexed with single phases, which have never been reported so far. Combination of both FT-IR and 27Al MAS/3QMAS nuclear magnetic resonance suggest that they all have an anion complex unit [Al(NH2)4]− as a basic component, indicating successful synthesis of the metal aluminum amides. Thermogravimetry-differential thermal analysis coupled with mass spectroscopy showed the release of NH3 below the temperatures of 140°C during the thermal decomposition and a NH3 desorption peak temperature (T des) decreased with the increasing atomic number. Additionally, a relationship between 27Al isotropic chemical shift and T des was discussed. The present study gives an useful information that the thermal stability of the anion complex [Al(NH2)4]− can be controlled by a cation M. [ABSTRACT FROM AUTHOR]

• Room temperature operation of all-solid-state Li-ion battery using MgH 2. • Composite electrode, compatibility of MgH 2 with electrolytes based on LiBH 4 , Li 2 S and P 2 S 5. • Comparative of battery performance using solid electrolytes LiBH 4 + 2(80Li 2 S + 20P 2 S 5) and 90LiBH 4 + 10P 2 S 5. ga1 All-solid-state Li-ion batteries along with conversion reaction electrodes, represent a promising next generation technology for energy storage. Among the conversion reaction type materials, MgH 2 is a leading contender owing to its high theoretical specific capacity (2036 mAhg−1) and a suitable potential to be used as anode material. However, some aspects related to solid electrolytes have restricted its possible application to high temperature (>100 °C) only. Recent research about solid-state electrolytes have brought some new ionic conductors having high conductivities at room temperature. In this study, LiBH 4 + 2(80Li 2 S + 20P 2 S 5) and 90LiBH 4 + 10P 2 S 5 were selected as electrolytes due to their similar and relatively high conductivities at room temperatures (~10−3 S cm−1, 30 °C). Coin cells were prepared and tested at 30 °C. The MgH 2 composite electrode prepared with 90LiBH 4 + 10P 2 S 5 showed a better performance than the composite with LiBH 4 + 2(80Li 2 S + 20P 2 S 5), with an initial capacity of 1135 mAhg−1 (457 Wh kg−1) and 540 mAhg−1 (205 Wh kg−1) respectively. A comparison between the single use of 80Li 2 S + 20P 2 S 5 and LiBH 4 , showed that LiBH 4 in composite electrodes can work nicely and deliver a better capacity than 90LiBH 4 + 10P 2 S 5. [ABSTRACT FROM AUTHOR]

The electrochemical reaction mechanism of lithium (Li)-ion with Bi 2 Se 3 anode material in all solid-state lithium-ion batteries (LIBs) has been successfully established in this work. Firstly, commercial bulk Bi 2 Se 3 was directly used as anode in LIB and then hydrothermally synthesized Bi 2 Se 3 nanostructures were used as anode material in order to improve the electrochemical performance of the battery. The structure of obtained nanostructures was characterized using powder x-ray diffraction, which verified the formation of Bi 2 Se 3 phase. Scanning electron microscopy and transmission electron microscopy studies confirmed the existence of mixed morphology, i.e., nanoparticles and nanosheets, with the diameter of nanoparticles in the range of 20–150 nm and the thickness of nanosheets, about 5–30 nm. Furthermore, electrochemical measurements indicated the initial discharge and charge capacity of bulk Bi 2 Se 3 as 621 mAhg−1 and 499 mAhg−1 respectively, which was slightly higher than the Bi 2 Se 3 nanostructures (discharge and charge capacities: 594 mAhg−1 and 468 mAhg−1). However, the nanostructures showed better cycling stability up to 50 cycles as compared to the bulk, which shed light on a new way to improve the lithium storage properties of the Bi 2 Se 3. We proposed the detailed electrochemical Li -storage mechanism in all solid state battery with bismuth selenide (Bi 2 Se 3) based composite material as high performance negative electrode for Li- ion battery using LiBH 4 as the solid state electrolyte reveals a high capacity and better cyclic stability with a high coulombic efficiency (∼97–98%). Image 1 • Detailed electrochemical mechanism of Bi 2 Se 3 anode is established. • LiBH4 is implemented as solid electrolyte with this anode material first time. • A highly stable performance with initial capacity of >600 mAhg−1 could be achieved. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical properties of Mg+2LiH and Al+3LiH are investigated by applying a Li-ion insertion and extraction system to form magnesium and aluminum hydrides. For MgH2 formation, the voltage–composition (VC) curve for Mg+2LiH during charging exhibits a plateau voltage at 0.58V, then the final composition is obtained with 1.05mol Li extraction at 3.0V. After the charging, the MgH2 phase is observed by XRD measurement. Therefore, MgH2 is produced from Mg and LiH by electrochemical charging. With respect to AlH3 formation, Al+3LiH is charged at a plateau voltage of 0.81V, which corresponds to the reaction of Al with hydrogen in LiH to form AlH3. And the final composition at 3.0V is 0.6mol Li. In the XRD profile after charging, the AlH3 phase is not detected. [Copyright &y& Elsevier]