Morphology Engineering of VS4 Microspheres as High-Performance Cathodes for Hybrid Mg2+/Li+ Batteries.

V-based sulfides are considered as potential cathode materials for Mg2+/Li+ hybrid ion batteries (MLIBs) due to their high theoretical specific capacities, unique crystal structure, and flexible valence adjustability. However, the formation of irreversible polysulfides, poor cycling performance, and severe structural collapse at high current densities impede their further development. Herein, VS4 microspheres with various controllable nanoarchitectures were successfully constructed via a facile solvothermal method by adjusting the amount of hydrochloric acid and were used as cathode materials for MLIBs. The VS4 microsphere self-assembled by bundles of paralleled-nanorods and some intersected-nanorods (VS4@NC-5) exhibits an outstanding initial discharge capacity of 805.4 mAh g-1 at 50 mA g-1 that is maintained at 259.1 mAh g-1 after 70 cycles. Moreover, the VS4@NC-5 cathode can deliver a superior rate capability (146.1 mAh g-1 at 2000 mA g-1) and ultralong cycling life (134.5 mAh g-1 at 2000 mA g-1 after 2000 cycles). The extraordinary electrochemical performance of VS4@NC-5 could be attributed to its special multi-hierarchical microsphere structure and the formation of N-doped carbon layers and V-C bonds, resulting in unobstructed ion diffusion channels, multidimensional electron transfer pathways, and enhancements of electrical conductivity and structure stability. Furthermore, the electrochemical reaction mechanism and phase conversion behavior of the VS4@NC-5 cathode at various states are investigated by a series of ex situ characterization methods. The VS4 well-designed through morphological engineering in this work can pave a way to explore more sulfides with high-rate performance and long cycling stability for energy storage devices.

Construction of TiO2/TiOF2 heterojunction as a cathode material for high-performance Mg2+/Li+ hybrid-ion batteries.

Anatase TiO2 has attracted significant interest as a cathode material for Mg-ion batteries or Mg2+/Li+ hybrid-ion batteries. However, owing to the semiconductor property and slower Mg2+ diffusion kinetics it still suffers from poor electrochemical performance. Herein, a TiO2/TiOF2 heterojunction consisting of in situ formed TiO2 sheets and TiOF2 rods, was prepared by adjusting the amount of HF in the hydrothermal process, and used as cathode of Mg2+/Li+ hybrid-ion battery. The TiO2/TiOF2 heterojunction prepared by adding 2 mL HF (TiO2/TiOF2-2) exhibits high electrochemical performance, with a high initial discharge capacity (378 mAh/g at 50 mA/g), an outstanding rate performance (128.8 mAh/g at 2000 mA/g), and good cycle stability (capacity retention of 54 % after 500 cycles), which is much superior to that of Pure TiO2 and Pure TiOF2. The reactions of Li+ intercalation/detercalation in the TiO2/TiOF2 heterojunction are revealed by investigating the evolution of the hybrids during different electrochemical states. Moreover, theoretical calculations prove that the Li+ formation energy in the TiO2/TiOF2 heterostructure is much lower than that of TiO2 and TiOF2, demonstrating that the heterostructure plays a crucial role in the enhanced electrochemical performance. This work provides a novel method to design cathode materials with high performance by constructing heterostructure.

Short-Range Nanoreaction Effect on the Hydrogen Desorption Behaviors of the MgH2-Ni@C Composite.

Doping a catalyst can efficiently improve the hydrogen reaction kinetics of MgH2. However, the hydrogen desorption behaviors are complicated in different MgH2-catalyst systems. Here, a carbon-encapsulated nickel (Ni@C) core-shell catalyst is synthesized to improve the hydrogen storage properties of MgH2. The complicated hydrogen desorption mechanism of the MgH2-Ni@C composite is elucidated. The experimental and theoretical calculation results indicate a short-range nanoreaction effect on the hydrogen desorption behaviors of the MgH2-Ni@C composite. The Ni@C catalysts and the adjacent MgH2 form nanoreaction sites along with preferential hydrogen desorption. The new interface between the in situ formed Mg and residual MgH2 contributes to the subsequent hydrogen desorption. With the nanoreaction sites increased via adding more catalyst, the short-range nanoreaction effect is more prominent; as a comparison, the interface effect becomes weaker or even disappears. In addition, the core-shell structure catalyst shows ultrahigh structural stability and catalytic activity, even after 50 hydrogen absorption and desorption cycles. Hence, this study provides new insights into the complicated hydrogen desorption behaviors and comes up with the short-range nanoreaction effect in the MgH2-catalyst system.

Supra Hydrolytic Catalysis of Ni3 Fe/rGO for Hydrogen Generation.

Light metal hydrolysis for hydrogen supply is well suited for portable hydrogen fuel cells. The addition of catalysts can substantially aid Mg hydrolysis. However, there is a lack of clear catalytic mechanism to guide the design of efficient catalysts. In this work, the essential role of nanosized catalyst (Ni3 Fe/rGO) in activating micro-sized Mg with ultra-rapid hydrolysis process is investigated for the first time. Here, an unprecedented content of 0.2 wt% Ni3 Fe/rGO added Mg can release 812.4 mL g-1 hydrogen in just 60 s at 30 °C. Notably, an impressive performance with a hydrogen yield of 826.4 mL g-1 at 0 °C in only 30 s is achieved by the Mg-2 wt% Ni3 Fe/rGO, extending the temperature range for practical applications of hydrolysis. Moreover, the four catalysts (Ni3 Fe/rGO, Ni3 Fe, Ni/rGO, Fe/rGO) are designed to reveal the influence of composition, particle size, and dispersion on catalytic behavior. Theoretical studies corroborate that the addition of Ni3 Fe/rGO accelerates the electron transfer and coupling processes and further provides a lower energy barrier diffusion path for hydrogen. Thus, a mechanism concerning the catalyst as migration relay is proposed. This work offers guidelines designing high-performance catalysts especially for activating the hydrolysis of micro-sized light weight metals.

Vacancy-Mediated Hydrogen Spillover Improving Hydrogen Storage Properties and Air Stability of Metal Hydrides.

Hydrogen storage in metal hydrides is a promising solution for sustainable and clean energy carriers. Although Mg-based metal hydrides are considered as potential hydrogen storage media, severe surface passivation has limited their industrial application. In this study, a simple, cheap, and efficient method is proposed to produce highly reactive and air-stable bulk Mg-Ni-based hydrides by rapid treatment with water for 3 min. The nickel-decorated Mg(OH)2 nanosheets formed in situ during hydrolysis can provide a pathway for hydrogen desorption via vacancy-mediated hydrogen spillover, as revealed by density functional theory calculations, thereby significantly decreasing the peak dehydrogenation temperature by 108.2 °C. Moreover, water-activated hydrides can be stored under ambient conditions without surface decay and activity loss, exhibiting excellent air stability, which can be attributed to the chemical stability of the surface layer. The results provide alternative insights into the design of highly active, air-stable metal hydrides with low cost and promote the industrial application of hydrogen energy.

Effect of Few-Layer Ti3C2Tx Supported Nano-Ni via Self-Assembly Reduction on Hydrogen Storage Performance of MgH2.

For the first time, few-layer Ti3C2Tx (FL-Ti3C2Tx) supporting highly dispersed nano-Ni particles with an interconnected and interlaced structure was elaborated through a self-assembly reduction process. FL-Ti3C2Tx not only acts as a supporting material but also self-assembles with Ni2+ ions through the electrostatic interaction, assisting in the reduction of nano-Ni. After ball milling with MgH2, Ni30/FL-Ti3C2Tx (few-layer Ti3C2Tx supported 30 wt % nano-Ni via self-assembly reduction) shows superior catalytic activity for MgH2. For example, MgH2-5 wt % Ni30/FL-Ti3C2Tx can release approximately 5.83 wt % hydrogen within 1800 s at 250 °C and absorb 5 wt % hydrogen within 1700 s at 100 °C. The combined effects of finely dispersed nano-Ni in situ-grown on FL-Ti3C2Tx, large specific area of FL-Ti3C2Tx, multiple-valence Ti (Ti4+, Ti3+, Ti2+, and Ti0) derived from FL-Ti3C2Tx, and the electronic interaction between Ni and FL-Ti3C2Tx can explain the superb hydrogen storage performance. Our results will attract more attention to the elaboration of the metal/FL-Ti3C2Tx composite via self-assembly reduction and provide a guideline to design high-efficiency composite catalysts with MXene in hydrogen storage fields.

Ultrahigh rate capability and long cycling stability of dual-ion batteries enabled by TiO2 microspheres with abundant oxygen vacancies.

Favourable effects of oxygen vacancies in TiO2-x synthesized via a calcination method on the electrochemical performance of dual Mg/Li-ion batteries are investigated. The dual-ion cell shows excellent rate capabilities up to 40 C and outstanding cyclability up to 2500 cycles.

Lithium migration pathways at the composite interface of LiBH4 and two-dimensional MoS2 enabling superior ionic conductivity at room temperature.

LiBH4 is one of the most promising solid electrolyte materials for use in solid-state batteries because its hexagonal phase above 110 °C offers Li-ion conductivity of almost 10-3 S cm-1. However, near room temperature, its orthorhombic phase delivers Li-ion conductivity of only 10-8 S cm-1, which considerably hampers its further applications. In the present study, a highly disordered interface between LiBH4 and two-dimensional MoS2 in the composite material was formed, yielding ionic conductivity of 10-4 S cm-1 at room temperature. LiBH4 and MoS2 are found to be in close contact without the formation of any intermediate phase at the interface. First-principles calculations employing density functional theory (DFT) and the nudged elastic band (NEB) method reveal that the migration energy barrier on three specific pathways could be established via microstructure analyses. It was found that the interface between the two phases yields the lowest Li-ion diffusion barrier among all the possible Li-ion pathways; further, the superior conductivity of the composite could be attributed to the interface with high Li-ion conductivity. This study proposes a new strategy for designing solid electrolytes and provides certain possibilities for two-dimensional materials to serve as superior solid electrolytes.

Catalytic effect of sandwich-like Ti3C2/TiO2(A)-C on hydrogen storage performance of MgH2.

A sandwich-like Ti3C2/TiO2(A)-C prepared through a facile gas-solid method was doped into MgH2 by ball milling. Ti3C2/TiO2(A)-C shows a far superior catalytic effect on the hydrogen storage of MgH2 than individual Ti3C2 or TiO2(A)-C, assigning as a synergistic catalysis between Ti3C2 and TiO2(A)-C. For example, the peak dehydrogenation temperature of MgH2-5 wt% Ti3C2/TiO2(A)-C is reduced to 308 °C, much lower than that of MgH2-5 wt% Ti3C2 (340 °C) or MgH2-5 wt% TiO2(A)-C (356 °C). After dehydrogenation, the dehydrogenated MgH2-5 wt% Ti3C2/TiO2(A)-C can uptake approximately 4 wt% of hydrogen within 800 s at 125 °C, while for the dehydrogenated MgH2-5 wt% Ti3C2 and MgH2-5 wt% TiO2(A)-C, only 3 wt% and 2.65 wt% hydrogen content can be obtained, respectively. Besides this, MgH2-5 wt% Ti3C2/TiO2(A)-C exhibits the lowest apparent activation energies (42.32 kJ mol-1 H2 for the hydrogen absorption and 77.69 kJ mol-1 H2 for the hydrogen desorption), which can explain the excellent hydrogen ab/desorption kinetic properties. The synergetic effects between the special layered structure and multiple valence titanium compounds (Ti4+, Ti3+, Ti2+, Ti0) verified by the x-ray photoelectron spectroscopy results are responsible for the catalytic mechanism on the hydrogen storage of MgH2. This study also supplies innovative insights into designing high efficiency MXene derivative catalysts in hydrogen storage.

Magnesium Nanoparticles With Pd Decoration for Hydrogen Storage.

In this work, Magnesium nanoparticles with Pd decoration, ranging from 40 to 70 nm, were successfully coprecipitated from tetrahydrofuran (THF) solution, assigned as the Mg-Pd nanocomposite. The Mg-Pd nanocomposite exhibits superior hydrogen storage properties. For the hydrogenated Mg-Pd nanocomposite at 150°C, the onset dehydrogenation temperature is significantly reduced to 216.8°C, with a lower apparent activation energy for dehydrogenation of 93.8 kJ/mol H2. High-content γ-MgH2 formed during the hydrogenation process, along with PH0.706, contributes to the enhancing of desorption kinetics. The Mg-Pd nanocomposite can take up 3.0 wt% hydrogen in 2 h at a temperature as low as 50°C. During lower hydrogenation temperatures, Pd can dissociate hydrogen and create a hydrogen diffusion pathway for the Mg nanoparticles, leading to the decrease of the hydrogenation apparent activation energy (44.3 kJ/mol H2). In addition, the Mg-Pd alloy formed during the hydrogenation/dehydrogenation process can play an active role in the reversible metal hydride transformation, destabilizing the MgH2.

Remarkable Synergistic Catalysis of Ni-Doped Ultrafine TiO2 on Hydrogen Sorption Kinetics of MgH2.

Catalysts play an extraordinarily important role in accelerating the hydrogen sorption rates in metal-hydrogen systems. Herein, we report a surprisingly synergetic enhancement of metal-metal oxide cocatalyst on the hydrogen sorption properties of MgH2: only 5 wt % doping of Ni into ultrafine TiO2 enables a significant increase in hydrogen desorption kinetics; it absorbs 4.50 wt % hydrogen even at a low temperature of 50 °C. The striking improvement is partially ascribed to the formation of a particular Ni@TiO2 core-shell structure, thereby forming versatile interfaces. This study provides insights into the way of designing high-efficiency catalysts in hydrogen storage and other energy-related fields.

Enhancing hydrogen storage performances of MgH2 by Ni nano-particles over mesoporous carbon CMK-3.

Nano-dispersed Ni particles over mesoporous carbon material CMK-3 (Ni/CMK-3) was fabricated by means of impregnation-reduction strategy using precursor NiCl2 · 6H2O, which is beneficial to improving the de/rehydrogenation performances of MgH2. The dehydrogenation onset temperature of MgH2-Ni/CMK-3 is significantly lowered by 170 K from that of pristine MgH2 (around 603 K). Totally 5.9 wt% of hydrogen absorption capacity is liberated within 1 h at a temperature of 423 K under a pressure of 3 MPa. This composite can absorb 3.9 wt% hydrogen even at a temperature of 328 K under 3 MPa H2. Activation energy values of both dehydrogenation (43.4 kJ mol-1) and rehydrogenation (37.4 kJ mol-1) for MgH2-Ni/CMK-3 are greatly enhanced from those of as-milled MgH2. Ni/CMK-3 also slightly destabilizes the dehydrogenation of MgH2 by 1.5 kJ mol [Formula: see text] The enhanced performances can be attributed to the synergistic effects of both destabilization and activation from nano-dispersed Ni particles.

Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg2 NiH4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg2 NiH4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol-1 ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents.

Excellent catalytic effects of multi-walled carbon nanotube supported titania on hydrogen storage of a Mg-Ni alloy.

Superior catalytic effects of multi-walled carbon nanotube supported titania synthesized by the sol-gel method on hydrogen storage of a Mg-Ni alloy were investigated. The excellent hydrogen storage properties were obtained: absorbed 5.60 wt% H2 within 60 s at 373 K and released 6.08 wt% H2 within 600 s at 553 K.

Highly efficient bimetal synergetic catalysis by a multi-wall carbon nanotube supported palladium and nickel catalyst for the hydrogen storage of magnesium hydride.

A multi-wall carbon nanotube supported Pd and Ni catalyst efficiently catalyzes the hydrogen storage of magnesium hydride prepared by HCS + MM. Excellent hydrogen storage properties were obtained: hydrogen absorption - 6.44 wt% within 100 s at 373 K, hydrogen desorption - 6.41 wt% within 1800 s at 523 K and 6.70 wt% within 400 s at 573 K.

A hydrothermal synthesis of Pr3+ doped mesoporous TiO2 for UV light photocatalysis.

Pr3+ doped mesoporous TiO2 photocatalysts with a different molar ratio of Pr to Ti were prepared by a hydrothermal method using triblock copolymer as the template. The as-prepared samples were systematically characterized by X-ray diffraction, N2 adsorption-desorption, X-ray photoelectron spectra, transmission electron microscopy and UV-visible diffuse reflectance spectroscopy. The characterizations indicated all the samples had mesoporous structure and narrow pore size distribution. Pr3+ doping enlarged the surface area and decreased the crystallite size. The surface area of the samples varied from 136 to 170 m2/g, and the average crystallite size ranged between 5.04 and 7.60 nm. The effect of Pr3+ doping amount on the photocatalytic activity of mesoporous TiO2 was evaluated by the degradation of methyl orange under UV light irradiation. The results showed that the suitable amount of Pr3+ doped samples exhibited the higher photocatalytic activity than mesoporous TiO2. Among the samples, 1 at.% Pr3+ doped mesoporous TiO2 showed the highest photocatalytic activity.

Efficient catalysis by MgCl2 in hydrogen generation via hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis.

Magnesium chloride efficiently catalyzed the hydrolysis of Mg-based hydride prepared by hydriding combustion synthesis. Hydrogen yield of 1635 mL g(-1) was obtained (MgH(2)), i.e. with 96% conversion in 30 min at 303 K.

Low-level lead exposure attenuates the expression of three major isoforms of neural cell adhesion molecule.

Toxic lead (Pb) exposure poses serious risks to human health, especially to children at developmental stages, even at low exposure levels. Neural cell adhesion molecule (NCAM) is considered to be a potential early target in the neurotoxicity of Pb due to its role in cell adhesion, neuronal migration, synaptic plasticity, and learning and memory. However, the effect of low-level Pb exposure on the specific expression of NCAM isoforms has not been reported. In the present study, we found that Pb could concentration-dependently (1-100 nM) inhibit the expression of three major NCAM isoforms (NCAM-180, -140, and -120) in primary cultured hippocampal neurons. Furthermore, it was verified that levels of all three major isoforms of NCAM were reduced by Pb exposure in human embryonic kidney (HEK)-293 cells transiently transfected with NCAM-120, -140, or -180 isoform cDNA constructs. In addition, low-level Pb exposure delayed the neurite outgrowth and reduced the survival rate of cultured hippocampal neurons at different time-points. Together, our results demonstrate that developmental low-level Pb exposure can attenuate the expression of all three major NCAM isoforms, which may contribute to the observed Pb-mediated neurotoxicity.