Search

The increasing severity of global climate and energy problems has made renewable energy an inevitable choice for achieving a low-carbon society. Hydrogen is regarded as one of the most promising renewable energy due to its excellent characteristics, such as abundant and extensive resources, high calorific value, and non-pollution. How to achieve efficient hydrogen storage is one of the main hot spots of hydrogen energy research. For on-board hydrogen storage systems, which could be used for portable power sources and fuel cell vehicles, how to store hydrogen safely and effectively is one of the most urgent technological bottlenecks to overcome. The solid-state storage based on hydrogen storage materials has the advantages of low hydrogen storage pressure, high energy efficiency, safety and reliability, compared to conventional compressed hydrogen and cryogenic liquid hydrogen storage methods. It may be one of the most promising solutions to solve the above problems. Among the hydrogen storage materials, the lightweight composite hydrides Li–Mg–N–H system holds great promise for vehicular hydrogen storage applications owing to its moderate thermodynamic properties (∆Hdes ~ 44 kJ mol−1 H2 and ∆Sdes ~ 112 J mol−1 H2·K) and relatively high hydrogen capacity (~ 5.6 wt%). However, the Li–Mg–N–H material itself has poor cycling performance and a high energy barrier, resulting in a low dehydrogenation rate and high operating temperature. Apart from this, the multi-field coupling of mass and energy transfer also poses a challenge, hindering its on-board applications. In this paper, we present the modification methods and research status of the Li–Mg–N–H system's hydrogen storage materials. The effects of composition modification, nanocrystallization and catalyst addition on the thermal/kinetic properties of hydrogen storage materials in the Li–Mg–N–H system are expounded. The difficulties and directions for enhancing the hydrogen storage performance of Li–Mg–N–H system are discussed. [ABSTRACT FROM AUTHOR]

Summary: TixCr1 − yFeyMn1.0 (x = 1.02, 1.05, 1.1, 0.05 ≤ y ≤ 0.25) alloys were prepared by plasma arc melting and annealing at 1273 K for 2 hours. The XRD results show that the main phase of all alloys is the C14 type Laves phase, and a little secondary phase exists in a mixture of the binary alloy phase. The lattice parameters increase with Ti super‐stoichiometry ratio increasing, whereas smaller lattice parameters emerge with increasing Fe stoichiometry content. Additionally, as the Ti super‐stoichiometry ratio decreases, the pressure‐composition‐temperature measurements indicated that hydrogen absorption and desorption plateau pressures of TixCr0.9Fe0.1Mn1.0 (x = 1.1, 1.05, 1.02) alloys increase from 3.15, 0.67, to 5.94, 1.13 MPa at 233 K, respectively. On the other hand, with the Fe content increasing in Ti1.05Cr1 − yFeyMn1.0 (0.1 ≤ y ≤ 0.25) alloys from 0.1 to 0.25, the hydrogen desorption plateau pressures increased from 1.41 to 2.46 MPa at 243 K. The hydrogen desorption plateau slopes reduce to 0.2 with Ti super‐stoichiometry ratio decreasing to 1.02, but the alloys are very difficult to activate for hydrogen absorption and cannot activate when the Fe substituting for Cr exceeds 0.2. The maximum hydrogen storage capacities were more than 1.85 wt% at 201 K. The reversible hydrogen storage capacities can remain more than 1.55 wt% at 271 K. The enthalpy and entropy for all hydride dehydrogenation are in the range of 21.0 to 25.5 kJ/mol H2 and 116 to 122 J mol−1 K−1, respectively. Our results suggest that Ti1.05Cr0.75Fe0.25Mn1.0 alloy with low enthalpy holds great promise for a high hydrogen pressure hybrid tank in a hydrogen refueling station (45 MPa at 333 K), and the other alloys of low cost may be used for a potable hybrid tank due to high dissociation pressure at 243 K and high volumetric density exceeding 40 kg/m3. [ABSTRACT FROM AUTHOR]

Abstract: Mg–20wt% Ni–Y composite was successfully prepared by reactive mechanical alloying (RMA). X-ray diffraction (XRD) measurement showed that both MgH2 and Mg2NiH4 co-exist in the milled composite. The composite exhibits excellent hydrogen sorption kinetics and does not need activation on the first hydrogen storage process. It can absorb 3.92 and 5.59wt% hydrogen under 3.0MPa hydrogen pressure at 293 and 473K in 10 min, respectively, and desorb 4.67wt% hydrogen at 523K in 30min under 0.02MPa hydrogen pressure. The equilibrium desorption pressure of the composite are 0.142, 0.051 and 0.025MPa at 573, 543 and 523K, respectively. The differential scanning calorimetry (DSC) measurement showed that dehydrogenation of Mg–20wt% Ni–Y composite was depressed about 100K comparing to that of milled pure MgH2. It is deduced that both the catalysis effect of Mg2Ni and YH3 distributed in Mg substrate and the crystal defects formed by RMA are the main reason for improving hydrogen sorption kinetics of the Mg–20wt% Ni–Y composite. [Copyright &y& Elsevier]

Solid-state hydrogen storage device using metal hydride have enormous advantages for fuel cell forklifts. In addition to high volume hydrogen storage density, the solid-state hydrogen storage device can also be used as a counterweight for the forklift. At the same time, the solid-state storage device has low hydrogen storage pressure and safety, and the fuel (H 2) refueling is convenient and low-cost. In this paper, a two-dimensional heat and mass transfer numerical model has been developed to predicting the performance of the metal hydride tank filled with Ti 0.9 Zr 0.1 Cr 0.35 Mn 1.4 V 0.2 Fe 0.05 alloy. The validity of this numerical model was tested by comparison with the experimental data of the metal hydride hydrogen storage tank with a hydrogen capacity of 1 kg, achieving a good agreement between all the data. And a solid-state hydrogen storage device with an effective hydrogen capacity of 1.5 kg is optimally designed for 3.5 T fuel cell forklift. The completion rate of hydrogen refueling in the solid-state hydrogen storage device will reach 97.6 % within 30 min, and continuously discharging over 1.5 kg H 2 under flow rates of 150 SL/min and 250 SL/min. The optimized solid-state hydrogen storage device was integrated in a power module for 3.5 T fuel cell forklift which allows uninterrupted operation for at least 6 h 8 min under rated operation. • Establish and verify a heat and mass transfer model of metal hydride bed. • The solid-state H 2 storage device is optimized using the numerical model. • The H 2 storage device can release over 1.5 kg H 2 and refuel 97.6 % in 30 min • The fuel cell forklift can operate continuously over 6 h. [ABSTRACT FROM AUTHOR]

The ambition of carbon neutrality has become a common pursuit for researchers worldwide, and hydrogen as a green and clean energy carrier is expected to contribute to this achievement. Since hydrogen fuel cell vehicles require a high input hydrogen pressure, compressors in hydrogen refueling stations are thus indispensable for the large-scale application of hydrogen energy. Compared to conventional mechanical hydrogen compressors, metal hydride based hydrogen compressors have the advantages of high security and low cost, providing a viable solution for hydrogen refueling station development. Herein, two series of Ti 0.95 Zr 0.07 Cr 1.3- x Mn x Fe 0.4 (x = 0.2, 0.3, 0.4, 0.6) and Ti 0.95 Zr 0.07 Cr 1.0 Mn 0.6 Fe 0.4- y Cu y (y = 0.1, 0.15, 0.2, 0.3) alloys were designed to achieve 8–22 MPa hydrogen compression in water bath at 283–353 K. All the as-prepared alloys exhibit the single hexagonal C14 Laves phase structure. In particular, the double substitution of Cr and Fe by Cu and Mn elements in Ti–Zr–Cr–Mn–Fe alloy can enlarge its hydrogen storage capacity without varying the equilibrium pressure. For instance, Ti 0.95 Zr 0.07 Cr 1.0 Mn 0.6 Fe 0.25 Cu 0.15 alloy has a hydrogenation plateau pressure of 6.16 MPa at 283 K and a dehydrogenation plateau pressure of 24.23 MPa at 353 K, with the max hydrogen capacity of 1.72 wt%. Furthermore, the relative high density molding method of metal hydride bed with 20 g of alloy powder was developed. The binder epoxy resin and the thermal conductor flake graphite were selected and added into the alloys to form metal hydride compacts (MHCs). The structural stability of modified MHCs can be enhanced due to the formation of a three-dimensional grid structure, with a higher resistance to pulverization and degradation. The improved thermal conductivity involving a filling compact strategy can significantly shorten hydrogenation reaction time by 50% and lower the abrupt temperature of metal hydride bed by 20 K with excellent stability over 100 cycles, and provide new insights of the development of safe and efficient hydride hydrogen compressor. [Display omitted] • The double substitution of Cr and Fe by Cu and Mn enhances thermodynamic hydrogen storage performance. • Optimal Ti-based alloy has de-hydrogenation plateau pressures of 24.23 MPa (353 K) and 5.74 MPa (283 K) with 1.72 wt% capacity. • A three-dimensional grid structure of epoxy resin and flake graphite is introduced to enhance the efficiency of the MHHC. [ABSTRACT FROM AUTHOR]

Hydrogen is the ideal green fuel and carbon-neutral energy carrier alternative to nonrenewable fuel sources. The high construction cost of hydrogen refueling stations has become one of the limitations to the further promotion and application of hydrogen energy. To realize 8–22 MPa hydrogen compression under mild conditions, the low cost Ti 0.95 Zr 0.07 Cr 1.7- x Mn 0.3 Fe x (x = 0–0.5) alloys were designed and prepared by magnetic levitation melting in this work. The effect of Fe on Cr substitution on the microstructure and hydrogen storage properties of the alloy has been systematically investigated. With the increase of Fe substitution for Cr, all the alloys maintain a single C14 Laves phase, the thermodynamic plateau curve broadens and rises, while the hydrogen storage capacity diminishes slightly. For a better description of the thermodynamic properties of alloys at high temperatures as the function of temperature, a non-linear Van't Hoff fitting is introduced with satisfactory prediction. On account of significant Fe substitution for Cr, the unit cell shrinks and the interstitial size of alloy decreases, an optimal alloying constituent, Ti 0.95 Zr 0.07 Cr 1.3 Mn 0.3 Fe 0.4 , has been proposed and experimentally proved for the first time. This alloy exhibits the best overall performances and the plateau pressure is respectively 5.74 MPa for hydrogenation at 283 K and 25.97 MPa for dehydrogenation at 353 K without apparent hysteresis phenomenon. The hydrogen storage capacity is 1.59 wt% within 3 min and dehydrogenation enthalpy is 21.20 kJ/mol H 2. This study provides a comprehensive insight into the low-cost hydrogen storage alloy design and application on quick response and high cycle stability metal hydride hydrogen compressors. [Display omitted] • Ti 0.95 Zr 0.07 Cr 1.7- x Mn 0.3 Fe x alloys were explored to realize 8–22 MPa hydrogen compression. • The effects of Fe on Cr substitution on hydrogen compression properties were revealed. • A non-linear Van't Hoff fitting was developed to forecast high hydrogen compression property. [ABSTRACT FROM AUTHOR]