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Abstract Spent Zn‒Mn batteries (ZMBs) pose a serious threat on eco-system and human health because of the toxic heavy metal ions released from ZMBs into the environment. In this report, carbon package is recycled from spent ZMBs and used as a positive electrode material for flexible supercapacitors. In a three-electrode system using 1 mol L−1 Na 2 SO 4 as the electrolyte, the recycled carbon package (RCP) can deliver a specific capacitance of 100 F g−1 at 1 A g−1. After 5000 cycles at 1 A g−1, a specific capacitance of 86 F g−1 is retained with nearly 100% coulombic efficiency. Nanocomposite of NaTi 2 (PO 4) 3 with nitrogen-doped carbon layer (NTP/C) is prepared through a simple co-precipitation plus annealing method. NTP/C can deliver specific capacity of 320 and 273 F g−1 at 1 and 10 A g−1, using 1 mol L−1 Na 2 SO 4 as the electrolyte. The high rate capability of NTP/C is attributed to the high specific surface area and nitrogen-doped carbon layer. Flexible asymmetric supercapacitors are assembled in configuration of NTP/C‖RCP, using 1 mol L−1 Na 2 SO 4 as the electrolyte and stainless steel foil as the current collector. At 0.5 A g−1, the typical flexible supercapacitor cell can deliver a specific energy of 17.8 W h kg−1 with corresponding specific power of 503 W kg−1, and retain 15 W h kg−1 after 2000 cycles. Graphical abstract Flexible asymmetric supercapacitor (electrode geometric area: 1 × 1 cm2) connected in two series can lighten 24 blue LEDs (normal voltage 3.0–3.2 V, rated current 20 mA) for more than 8 min that are assembled by using carbon package recycled from spent Zn‒Mn batteries as the positive electrode and NaTi 2 (PO 4) 3 /C with nitrogen doping as the negative electrode. Image 1 Highlights • Carbon package is recycled from spent Zn‒Mn batteries (ZMBs). • The recycled carbon package (RCP) is suitable for application in supercapacitors. • NaTi 2 (PO 4) 3 /C with nitrogen doping exhibits excellent electrochemical performance. • NaTi 2 (PO 4) 3 /C‖RCP retains 15 W h kg−1 after 2000 cycles at 0.5 A g−1. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Al additive on microstructures and hydrogen storage characteristics of Ti26.5Cr20(V0.45Fe0.085)100−x Al x Ce0.5 (x =0, 0.5, 1.0 and 1.5at.%) alloys have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and P–C-isotherm measurements. All of Al-added alloys consist of major BCC and secondary Al–Ce–O phases. The EDS analysis results show that aluminum is poor in the BCC phase but enriches in the secondary Al–Ce–O phase. As Al additive content increased, both the lattice parameters of the BCC phase and the hydrogen desorption equilibrium pressures increase, but the hydrogen storage capacities decrease. It is revealed that the substitution solid solution with BCC structure is formed by the substitution of Al for V atoms. It decreases the hydride stability of the BCC phase and degrades the hydrogen storage performance of the Al-added Ti26.5Cr20(V0.45Fe0.085)100−x Al x Ce0.5 alloys. [Copyright &y& Elsevier]

Abstract: The thermodynamics of hydrogenation for the Ti1−x Zr x MnCr (x =0, 0.1, 0.2, 0.32, 0.5, 0.7, 0.9, 1.0) alloys, which are characterized by the XRD Rietveld analysis as C14-type Laves phase, are evaluated by P–C isotherms measurements at different temperatures. Along with the increase of Zr content in the alloys, the pressure of the absorption/desorption plateau decreases monotonously; the average value of ǀΔHǀ increases linearly, and the average value of ǀΔSǀ decreases slightly; on the other hand, the hysteresis of hydrogenation reduces to a minimum at x =0.32, and then rises again; the slope of the plateau increases first, then decreases, forming a maximum at x =0.5. For the hydride formation of the Ti1−x Zr x MnCr alloys, the values of ǀΔHǀ and ǀΔSǀ increase with the hydrogen concentration, except for that of the Ti0.8Zr0.2MnCr, where an opposite trend occurs, but all the ǀΔHǀ values in the Ti1−x Zr x MnCr–H2 system are considerably lower than those in most Laves phase hydride systems. As combined effects of these trends, the Ti0.5Zr0.5MnCr alloy with the highest microstrain induced from the greatest mismatch of different atoms in the lattice, possesses the greatest plateau slope and the smallest variation width of ǀΔHǀ for the hydride formation; on the other hand, the Ti0.68Zr0.32MnCr alloy exhibits the best hydrogen storage properties, with a reversible hydrogen capacity of 216ml/g, and good plateau characteristics. [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]

Mg-20 wt% Ti x Cr 0.8-x V 0.2 (x = 0.25, 0.35, 0.45, 0.55) nanocomposites were synthesized by Reactive Ball Milling (RBM) under 5.0 MPa H 2 for 8 h at room temperature. The morphology, crystal structure, and isothermal hydrogen ab-/desorption properties of the as-milled nanocomposites were investigated. X-ray diffraction confirms that the composites were composed of nanocrystalline β-MgH 2 , γ-MgH 2 and Ti-Cr-V 0.2 H y (1.91 < y < 2.01) phases. High-Resolution Transmission Electron Microscopy (HRTEM) images reveal that nanocrystalline β-MgH 2 , γ-MgH 2 and Ti 0.35 Cr 0.45 V 0.2 H y phases coexist on nano-level in the as-milled composites. Differential scanning calorimeter (DSC) results show that MgH 2 -20 wt% Ti 0.35 Cr 0.45 V 0.2 composite presents the minimum decomposition temperature (256 °C) among the studied composites and a relatively low activation energy of 86.43 kJ/mol. The hydrogen desorption capacity of MgH 2 -20 wt% Ti 0.35 Cr 0.45 V 0.2 composite reach to 5.30 wt% within 20 min at 270 °C under 0.01 MPa H 2 , compared with that only 0.1 wt% H 2 for pure MgH 2 powders under the same conditions. Besides, the hydrogenation and dehydrogenation enthalpies are determined to be −69.35 and 70.60 kJ/(mol⋅H 2) respectively, which show a significant decrease compared with that of Mg/MgH 2 systems. More importanly, the β-MgH 2 phase is found to decompose along with γ-MgH 2 and Ti-Cr-V 0.2 H y phases at the temperature ranging from 210 to 270 °C. It reveals the favorable synergetic desorption effect among γ-MgH 2 , β-MgH 2 and Ti 0.35 Cr 0.45 V 0.2 H y phases, which possibly leads to better dehydrogenation kinetics and thermodynamics properties of Mg/MgH 2 systems. Nanocrystalline Mg-20wt%Ti x Cr 0.8-x V 0.2 composites were synthesized. Highest content of metastable γ-MgH 2 phase(36.19wt%) was obtained. The desorption temperature of Mg-20wt%Ti 0.35 Cr 0.45 V 0.2 is 84 °C lowers than pure MgH2. Good synergetic desorption effect among Ti 0.35 Cr 0.45 V 0.2 Hy, γ-MgH2 and β-MgH2 phases. [ABSTRACT FROM AUTHOR]

Chemical oxidation synthesis of graphene oxide (GO) through modified Hummers methods has been widely employed for producing graphene- or reduced GO (rGO)-based advanced functional materials such as rGO/MnO x nanocomposites. However, the manganese species in GO colloids are usually washed out during GO synthesis through modified Hummers methods, causing manganese waste and environmental risk. In this paper, we report preparation of rGO/MnO x nanocomposites, in which MnO x is composed of Mn 2 O 3 , Mn 3 O 4 , and MnO 2 components, through anneal treatment of the precursor counterparts obtained by simple pH tuning of GO colloids. The rGO/MnO x nanocomposites exhibit superior electrochemical performance for supercapacitors. rGO/MnO x -5, derived from GO colloids with pH 5, exhibits a high gravimetric discharge capacitance ( C dis ) of 191 F g −1 at 20 A g −1 and a high capacitance retention (82.9%) relative to C dis at 1 A g −1 . Furthermore, typical symmetric supercapacitor cells made from rGO/MnO x -5 show a high areal capacitance (172 mF cm −2 ) and excellent capacitance retention (96.6%) at 2 A g −1 (10 mA cm −2 ) for 20,000 cycles, holding great potential for practical applications. The superior electrochemical performance of rGO/MnO x nanocomposites is attributed to multiple charge storage mechanisms in association with the coexistence of mixed-valent manganese oxides. [ABSTRACT FROM AUTHOR]

• Crystal and electron structure affect hydrogen storage properties of V-based alloys. • Hydrogen capacity decreases and plateau pressure rises with BCT phase constriction. • Approximate parabolic relationship between hydrogen capacity and electron density. • Excellent cycle durability with capacity retention rate of 97% after 100 cycles. • Small attenuation is due to crystal refinement and small contraction of BCT phases. [Display omitted] V-based hydrogen storage alloys are considered promising materials with high hydrogen capacity under ambient conditions. 75 V-Ti-15Cr alloys with different Fe and Al addition (1–3 at%) have been investigated. All the alloys are confirmed to show body-centered tetragonal (BCT) structure after dehydrogenated at room temperature. The PCT tests manifest that the hydrogen storage capacity decreases and desorption plateau pressure rises with the content of Fe or Al. The relationship between the hydrogen storage property and lattice parameters of BCT phase is discussed. Also, the relationship between hydrogen capacity and electron density is analyzed. Among the studied alloys, the 75 V-Ti-15Cr-1Al-1Fe alloy shows optimal hydrogen storage capacity (2.26 wt%) and plateau pressure (0.5 MPa) at room temperature. Cycle test proves that the optimized 75 V-Ti-15Cr-1Al-1Fe alloy possesses excellent durability and the retention rate of hydrogen capacity can achieve 97% after 100 cycles. The slight capacity attenuation possibly results from the derivation of lattice defects and small contraction of the hydrogen absorption phases. [ABSTRACT FROM AUTHOR]

Abstract: The structural relationship between the hydride phases in Ti–Mo–H solid solution system (Mo content up to 15at% in the alloy) during dehydrogenation process under annealing has been studied by conventional and in situ X-ray powder diffraction and transmission electron microscopy (TEM) analysis. During dehydrogenation, the saturated hydrides of the Ti–Mo alloys with fcc δ-phase structure transfer into bcc β-phase at higher temperatures. An associated hydrogen concentration reduction for the δ-phase hydride is observed in the process. However, as the hydrogen concentrations decrease to certain values (H/M∼1.1–1.7), the unsaturated δ-phase formed at high temperature would become unstable at lower temperature, and transfer into a tetragonal phase (denoted the ɛ-phase here). Unlike that of the ɛ-phase in Ti–H system, the phase transition does not occur for the saturated δ-phase with hydrogen concentration close to the stoichiometric limit. The hydrogen concentration of this ɛ-phase hydride is in between that of the tetragonal γ and ɛ-phase in Ti–H system, but more close to the γ-phase. The occurrence region of this ɛ-phase expands along with the increase of the Mo content in the alloys. The phase has a lattice similar to that of the ɛ-phase in Ti–H system with corresponding fct unit-cell c/a <1. [Copyright &y& Elsevier]