Due to their high theoretical capacity and abundant resources,transition metal sulfides are regarded as a prospering alternative to replace the commercial graphite anode in lithium-ion batteries(LIBs),particularly for...Due to their high theoretical capacity and abundant resources,transition metal sulfides are regarded as a prospering alternative to replace the commercial graphite anode in lithium-ion batteries(LIBs),particularly for large-scale energy storage and conversion applications.Nonetheless,low conductivity,easy agglomeration and obvious volume change greatly impede their practical application.In this work,a novel crystalline/non-crystalline carbon co-modified strategy is proposed to fabricate N,S co-doped carbon(NSC)layer wrapped Fe_(0.95)S_(1.05)/carbon nanotubes(CNTs)composite(Fe_(0.95)S_(1.05)/CNTs@NSC)through a simple Fenton reaction followed by a sulfurization process.Systematical characterizations and analyses reveal that this strategy well combines the advantages of crystalline CNTs and non-crystalline NSC,ensuring good conductivity and a high contribution to capacity from the carbon matrix.Meanwhile,the joint encapsulation of Fe_(0.95)S_(1.05)by both CNTs and NSC can significantly mitigate the agglomeration and volume change of Fe_(0.95)S_(1.05)during the continuous charge/discharge process.Benefiting from these advantageous features,the resultant Fe_(0.95)S_(1.05)/CNTs@NSC composite displays much improved cycling stability and rate capability when compared to the counterparts.Clearly,our research offers a distinct and innovative approach to design and construct advanced transition metal sulfides/carbon composite anodes for LIBs.展开更多
High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficienc...High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficiency,making them suitable for energy storage applications.Despite significant advancements in experimental research,understanding of the properties associated with structure remains incomplete.This study aims to study the structural,electric,and mechanical performances at various scales of the high-entropy(Na_(0.2)Bi_(0.2)Ca_(0.2)Sr_(0.2)Ba_(0.2))TiO_(3)(NBCSB)material.The results of first-principles calculations indicated that the pseudo-intralayer distortion was obviously smaller compared to the interlayer distortion.Among the various bonds,Bi-O,Ca-O,and Na-O experienced the greatest displacement.Similarly,the hybridization between O 2p and Ti 3d states with Bi 6p states was particularly strong,affecting both the ferroelectric polarization and relaxor behavior.The NBCSB materials produced using a typical solid-state process demonstrated exceptional performance in energy storage with a recoverable density of 1.53 J·cm^(-3)and a high efficiency of 89%when subjected to a small electric field of 120 kV·cm^(-1).In addition,these ceramics displayed a remarkable hardness of around 7.23 GPa.NBCSB ceramics exhibited exceptional relaxation characteristics with minimal hysteresis and low remanent polarization due to its nanoscale high dynamic polarization configuration with diverse symmetries(rhombohedral,tetragonal,and cubic)resulting from randomly dispersed A-site ions.The excellent mechanical property is related to the dislocation-blocking effect,solid solution strengthening effect,and domain boundary effect.The findings of this study offer a comprehensive and novel perspective on A-site disordered high-entropy relaxor ferroelectric ceramics.展开更多
Hydrothermal-sintering method was employed to obtain pure and Li,Co,Mn,Cu and Zn doped La_(2)Ti_(2)O_(7) solid solutions.The substitution sites of doping ions are discussed.X-ray diffraction(XRD)results indicate that ...Hydrothermal-sintering method was employed to obtain pure and Li,Co,Mn,Cu and Zn doped La_(2)Ti_(2)O_(7) solid solutions.The substitution sites of doping ions are discussed.X-ray diffraction(XRD)results indicate that the doped ions were incorporated into the lattice of La_(2)Ti_(2)O_(7) successfully.Transmission electron microscopy(TEM)measurements prove that the doped ions with smaller radius induce the contraction of lattice.The re sults of UV and photo luminescence(PL)tests show that the doped ions cause the red-shift of band gap energies and enhance the concentrations of oxygen vacancies and defects.The electrochemical hydrogen storage properties of the samples were measured at 303 and 333 K,respectively.The discharge capacities of the doped samples keep growing by increasing the cycle number at 333 K.Meanwhile,the doped samples possess better kinetic performances than the pure La_(2)Ti_(2)O_(7).Among the samples,the Mn,Co and Li ions doped samples exhibit better electrochemical hydrogen storage properties.The hydrogen storage properties are closely related with the characteristics of doped ions,crystallite sizes,the content of the oxygen vacancies and defects in the lattice of La_(2)Ti_(2)O_(7).展开更多
This review details the advancement in the development of V–Ti-based hydrogen storage materials for using in metal hydride(MH)tanks to supply hydrogen to fuel cells at relatively ambient temperatures and pressures.V...This review details the advancement in the development of V–Ti-based hydrogen storage materials for using in metal hydride(MH)tanks to supply hydrogen to fuel cells at relatively ambient temperatures and pressures.V–Tibased solid solution alloys are excellent hydrogen storage materials among many metal hydrides due to their high reversible hydrogen storage capacity which is over 2 wt%at ambient temperature.The preparation methods,structure characteristics,improvement methods of hydrogen storage performance,and attenuation mechanism are systematically summarized and discussed.The relationships between hydrogen storage properties and alloy compositions as well as phase structures are discussed emphatically.For large-scale applications on MH tanks,it is necessary to develop low-cost and high-performance V–Ti-based solid solution alloys with high reversible hydrogen storage capacity,good cyclic durability,and excellent activation performance.展开更多
MgH_(2)is a promising solid-state hydrogen storage material.However,its high thermodynamics and sluggish kinetics hinder its practical application.Catalytic strategy is effective in improving its kinetic performance.N...MgH_(2)is a promising solid-state hydrogen storage material.However,its high thermodynamics and sluggish kinetics hinder its practical application.Catalytic strategy is effective in improving its kinetic performance.Nevertheless,the highly efficient catalysts or additives are normally of low-yield in fabrication with high cost.In this work,a novel structural LaVO_(4)fabricated by a low-cost method of spraying dry followed by a calcination is used as a catalytic additive for the hydrogen storage of MgH_(2).With an optimized addition of LaVO_(4),the overall hydrogen storage performances of MgH_(2)are significantly improved.An onset dehydrogenation temperature of only 183℃is obtained after an initial activation of dehydrogenation and hydrogenation.The system can desorb 5.7 wt%H_(2)at 250℃within 10 min and maintains a dehydrogenation capacity of 5.0 wt%H_(2)after 50 cycles.It is found that LaVO_(4)is transferred to lanthanum hydride and metallic vanadium in the initial dehydrogenation process,the former acts as a highly effective catalyst for the hydrogen storage of MgH_(2)and the latter undergoes reversible hydrogenation and dehydrogenation in the subsequent cycles.The structural design of the catalyst and its scalable fabrication are highly valuable in realizing the practical application of catalytic strategy for the hydrogen storage of MgH_(2).展开更多
Introduction Pure NBT exhibits the frequency-dependent Curie temperature,indicating that its dielectric properties are affected by temperature,measurement frequency,and material processing condition.To enhance the die...Introduction Pure NBT exhibits the frequency-dependent Curie temperature,indicating that its dielectric properties are affected by temperature,measurement frequency,and material processing condition.To enhance the dielectric and relaxor properties of NBT,various dopants such as Sr,K,Li and Bi are incorporated into the NBT structure.These modifications significantly alter the dielectric constant and relaxation behavior,demonstrating a dominant influence of dopant on the material properties.Among these,the solid solution of BaTiO_(3)(BT)with NBT is widely investigated due to its ability to stabilize the perovskite structure and improve dielectric performance.However,the temperature-dependent stability of dielectric properties remains a critical challenge for high-temperature applications.In this study,(1-x)(0.75Na_(0.5)Bi_(0.5)TiO_(3)-0.25BaTiO_(3))-xBaZrO_(3)(NBT-BT-xBZ,x=0,0.08,0.14,and 0.20)ceramics were prepared by a solid-state reaction method.The effect of BaZrO_(3)(BZ)addition on the structural,dielectric,and energy storage properties was systematically investigated.In addition,the phase transition and relaxation behaviors were also analyzed based on the modified Curie-Weiss law,Vogel-Fulcher relation,and Lorentz-type empirical law.Methods The starting materials were powders of high purity Na_(2)CO_(3),Bi_(2)O_(3),TiO_(2),BaCO_(3),and ZrO_(2).The powders were weighed according to a stoichiometric ratio(with 1%excess of Na and Bi)and ground with ethanol in a ball mill at 300 r/min for more than 12 h,and the weight ratio of raw material to ethanol and zirconium balls was 1:1:2.The dried material was heat-treated at 850℃ for 2 h to promote the formation of NBT-BT-BZ.After further grinding for 12 h,the samples were mixed with a small amount of polyvinyl alcohol(PVA).The samples were sintered in air at 1150℃for 2 h and cooled to room temperature.The phase composition of the ceramic samples was determined by an model D8 ADVANDCE X-ray diffractometer(D8 ADVANDCEXRD,Bruker AXS Ltd.,Germany)with Cu target Kαrays,at X-ray wavelengthλof 1.5406Å,2θin the range of 10°to 80°,applied voltage of 40 kV,and a current of 500 mA.A silver paste was coated on the two surfaces as electrodes and heat-treated at 700℃ for 10 min.The dielectric properties of the ceramic samples were determined at different frequencies by a model DMS-1000 high-temperature dielectric temperature spectroscope(BALAB Tech.Co.,China)with at a ramp rate of 3(°)/min in a temperature range from room temperature to 450℃.The overdamped(200Ω)discharge tests for bulk ceramic samples were performed by a model CFD-005 discharge tester(Gogo(GG)Instruments Technology,China)).Results and discussion The XRD patterns indicate that all the ceramic samples have a perovskite structure without any detectable secondary phase,proving that zirconium ions can completely enter the lattice and form a solid solution.Based on the locally magnified XRD peaks,the XRD peak shape shifts towards lower angles as a whole as the BZ content increases.This indicates that the overall volume of the crystal cell shows an expansion as the Zr ions replace Ti ions due to different ionic radii of Zr and Ti ions.The SEM images show that the grain size gradually increases with increasing the BZ content.The addition of BZ promotes the grain growth.However,this gradually slows down with the increase of content up to x of 0.20.The limited grain size variation appears in the latter two samples.All the samples show a relatively dense morphology.The Curie temperature of the NBT-0.25BT ceramic samples is 256℃,which is similar to the reported results.The Curie temperature decreases gradually with the increase of BZ additive,and the dielectric temperature spectrum flattens out,indicating that the enhanced structural and temperature stability of the NBT-BT-BZ ceramics.The maximum values of all dielectric constants correspond to temperatures that increase with frequency,indicating a dielectric relaxor behavior.A frequency dispersion is accompanied at near the Curie temperature,which can be ascribed to the thermal evolution of the tetragonal polar nanoregions(PNRs)and the mixing effect of the transition from tripartite to tetragonal PNRs.Theγvalues obtained from the experimental data at 100 kHz are 1.79,1.83,1.89,and 1.92 for NBT-BT,NBT-BT-0.08BZ,NBT-BT-0.14BZ,and NBT-BT-0.20BZ,respectively.Theγvalue increases gradually with the addition of the BZ content,showing an enhanced relaxation of the NBT-BT-BZ ceramics.The comparison of discharge current curves and energy density of all the ceramics indicate that the addition of BZ significantly improves the discharge current and energy storage performance.A high discharging energy density(Wd)of 1.6 J·cm^(-3) with a fast discharging speed(τ0.9)of 75 ns is obtained for the ceramic samples with x of 0.14.This can be attributed to an increased relaxation as the BZ content increases.Conclusions NBT-BT-BZ ceramics were prepared by a solid-state reaction method.The XRD patterns revealed a phase transition from a tetragonal phase to a pseudocubic phase as the BZ content increased.The dielectric relaxation behavior of the ceramics could be described by three empirical laws(i.e.,modified Curie-Weiss law,Vogel-Fulcher relation and Lorentz-type empirical law).The dielectric relaxation followed the modified Curie-Weiss law and the Vogel-Fulcher relationship.The parametersγand Ea,which were obtained to evaluate the relaxation behavior,increased at a higher BZ content.The Lorentz-type relationship effectively described the temperature dependence of the dielectric constant on both the low-and high-temperature sides within a specific temperature range for all the ceramics.展开更多
ZrMn2 alloy was electro-synthesized directly from cathode pellets compacted with powdered mixture of MnO2 and ZrO2 in molten calcium chloride. Sintering temperature, cell voltage and electrolysis time were the dominan...ZrMn2 alloy was electro-synthesized directly from cathode pellets compacted with powdered mixture of MnO2 and ZrO2 in molten calcium chloride. Sintering temperature, cell voltage and electrolysis time were the dominant factors that affected the characteristics of the final product. The results confirmed the formation of pure ZrMn2 alloy through the electro-deoxidation of the mixed oxide pellets at 3.1 V for 12 h in 900 °C CaCl2 melt. The X-ray diffraction（XRD） and cyclic voltammetry analysis suggested that the electro-deoxidation proceeded from the reduction of manganese oxides to Mn, followed by ZrO2 or CaZrO3 reduction on the pre-formed Mn to ZrMn2 alloy. The cyclic voltammetry measurements using powder microelectrode showed that the prepared ZrMn2 alloy has a good electrochemical hydrogen storage property.展开更多
MgH_(2)is a promising solid-state hydrogen storage material;one of the limitations of its scale-application is the slow rate of hydrogen uptake and release.The addition of catalyst to improve the kinetics of MgH_(2)ha...MgH_(2)is a promising solid-state hydrogen storage material;one of the limitations of its scale-application is the slow rate of hydrogen uptake and release.The addition of catalyst to improve the kinetics of MgH_(2)has achieved remarkable results.However,these studies require high-speed ball milling(400-500 rpm)to achieve the combination of MgH_(2)and catalyst,and such harsh processing conditions are difficult to achieve in industrial production.In this work,the catalyst and MgH_(2)were efficiently combined at lower milling speed(300 rpm)by introducing tetrahydrofuran C4H8O(THF)as an auxiliary agent.Moreover,milling with THF promotes the nanocrystallization of MgH_(2),which further improves its performance.Results show that THF-assisted MgH_(2)absorbed 6.1 wt%at 90℃and desorbed 6.1 wt%at 275℃,while the MgH_(2)milling under the same speed without THF cannot absorb hydrogen and only desorbed 3.3 wt%.It reveals that the synergistic effect produced by nano-crystallization and nano-hydrogen pump is the key mechanism of improving the performance of MgH_(2)after introducing THF.This work proposes a novel synergistic strategy for modifying MgH_(2),offering practical insights for enhancing its hydrogen storage performance under low-speed ball milling.展开更多
Black phosphorus(BP)is recognized as a promising anode for sodium-ion batteries(SIBs)due to its high safety and theoretical capacity.However,traditional ball milling methodologies for fabricating BP composite anodes h...Black phosphorus(BP)is recognized as a promising anode for sodium-ion batteries(SIBs)due to its high safety and theoretical capacity.However,traditional ball milling methodologies for fabricating BP composite anodes have not satisfactorily addressed the challenges of poor rate performance and short cycle life.To fill this scientific gap,we herein pioneer incorporating the sodium fast ionic conductorβ"-Al_(2)O_(3)into ball-milled BP with carbon,which facilitates the formation of three-dimensional mass transfer channels in the resulting composite.To stabilize these channels,we develop a novel and environmentally friendly functional binder that outperforms traditional binders in thermal stability,wettability,and mechanical properties.The newly established binder is capable of remarkably mitigating volume expansion and interfacial side reactions in the BP/β"-Al_(2)O_(3)/C composite anode.Additionally,we identify synergistic effects of the binder interacting with the BP/β"-Al_(2)O_(3)/C composite during cycling,characterized by the in-situ formation of P-O-C bonds,which is the first instance of a strong,durable chemical bond between the binder and the active material to the best of our knowledge.These advancements allow the composite electrode to exhibit exceptional sodium storage,including high initial Coulombic efficiency and long-term cycling stability,which surpasses most previous phosphorus-based anodes fabricated via traditional approaches.Notably,when paired with a Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_7(NFPP)cathode,the full cell exhibits unexpectedly high energy and power densities,highlighting the BP potential in SIBs.The findings presented in the present work contribute to the promotion of economical and efficient applications of phosphorus-based anode materials.展开更多
Three types of carbon nano-onions（CNOs） including Ni@CNOs.Fe3C@CNOs and Fe0.64Ni0.36@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy c...Three types of carbon nano-onions（CNOs） including Ni@CNOs.Fe3C@CNOs and Fe0.64Ni0.36@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy catalysts.Comparative and systematic studies have been carried out on the morphology,structural characteristics and graphitic crystallinity of these CNOs products.Furthermore,the electrochemical hydrogen storage properties of three types of CNOs have been investigated.Measurements show that the Ni@CNOs have the highest discharge capacity of 387.2 mAh/g,coiTesponding to a hydrogen storage of 1.42%.This comparison study shows the advantages of each catalyst in the growth of CNOs.enabling the controllable synthesis and tuning the properties of CNOs by mediating different metals and their alloy for using in the fuel cell system.展开更多
The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results stow that the modified alloys can be activated without any thermal treatment at room temperature due t...The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results stow that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in (lie alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.展开更多
A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The...A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T≤623 K) for hydriding and Igp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-a)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31kJ/(mol.H2) and 59.9±2.99kJ/(mol.H2)respectively.展开更多
The La0.55Pr0.05Nd0.15Mg0.25Ni3.5（Co0.5Al0.5）x（x=0.0, 0.1, 0.3, 0.5） alloys were prepared by magnetic levitation melting under an Ar atmosphere, and the effects of Co and Al on the hydrogen storage and electrochem...The La0.55Pr0.05Nd0.15Mg0.25Ni3.5（Co0.5Al0.5）x（x=0.0, 0.1, 0.3, 0.5） alloys were prepared by magnetic levitation melting under an Ar atmosphere, and the effects of Co and Al on the hydrogen storage and electrochemical properties were systematically investigated by pressure composition isotherms, cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy testing. The results showed that the alloy phases were mainly consisted of （La,Pr）（Ni,Co）5, LaMg2Ni9, （La,Nd）2Ni7 and LaNi3 phases, and the cell volumes of （La,Pr）（Ni,Co）5, LaMg2Ni9, （La,Nd）2Ni7 and LaNi3 phases expanded with Co and Al element added. The hydrogen storage capacity initially increased from 1.36 （x=0） to 1.47 wt.% （x=0.3） and then decreased to 1.22 wt.% （x=0.5）. The discharge capacity retention and cycle stability of the alloy electrodes were improved with the increase of Co and Al contents. The La0.55Pr0.05Nd0.15Mg0.25Ni3.5（Co0.5Al0.5）0.3 alloy electrode possessed better electrochemical kinetic characteristic.展开更多
The present study dealt with investigations on the effects of annealing on the hydrogen storage properties of La 1.6 Ti 0.4 MgNi 9 alloys.The experimental alloys were prepared by magnetic levitation melting followed b...The present study dealt with investigations on the effects of annealing on the hydrogen storage properties of La 1.6 Ti 0.4 MgNi 9 alloys.The experimental alloys were prepared by magnetic levitation melting followed by annealing treatment.For La 1.6 Ti 0.4 MgNi 9 alloys,LaNi 5,LaNi 3 and LaMg 2 Ni 9 were the main phases,Ti 2 Ni phase appeared at 900℃.Annealing not only enhanced the maximum and effective hydrogen storage capacity,improved the hydrogen absorption/desorption kinetics,but also increased the discharge capacity.The cyclic stability had been improved markedly by annealing,e.g.,when the discharge capacity reduced to 60% of maximum discharge capacity,the charge/discharge cycles increased from 66（as-cast） to 89（annealed at 800℃） and 127 times（annealed at 900℃）.La 1.6 Ti 0.4 MgNi 9 alloy annealed at 900℃ exhibited better electrochemical properties compared to the other two alloy electrodes.展开更多
The hydriding and dehydriding behaviors of tetrahydrofuran modified Mg,its electronic struc- ture,crystal structure,micro-morphology as well as its stability have been investigated.The modifield Mg absorbs 3.5 wt-％ h...The hydriding and dehydriding behaviors of tetrahydrofuran modified Mg,its electronic struc- ture,crystal structure,micro-morphology as well as its stability have been investigated.The modifield Mg absorbs 3.5 wt-％ hydrogen at 643 K in 3.5 MPa H_2,its hydride gives off 3.2 wt-％ hydrogen at 643 K in a vaccum of 1.3 Pa after 20 cycles of hydriding and dehydriding. Tetrahydrofuran alters the electronic structure of Mg but keeps its crystal strueture unchanged.In hydriding products,a new hydride phase is found in addition to the known MgH_2 phase.The hydride formed from Mg is polv-erystalline.The wide-spreading slip bands and twins within crystals indicate that the transformation during absorption of hydrogen causes serious lattice distortions.展开更多
A novel approach based on thermal diffusion was used to achieve controllable Mg content in A_(2)B_(7)-type La-Mg-Ni-based alloys.The formation mechanism of the A_(2)B_(7)-type phase as a result of the thermal diffusio...A novel approach based on thermal diffusion was used to achieve controllable Mg content in A_(2)B_(7)-type La-Mg-Ni-based alloys.The formation mechanism of the A_(2)B_(7)-type phase as a result of the thermal diffusion process and the effect of Mg content on hydrogen storage performance were investigated.X-ray diffraction(XRD)patterns and Rietveld refinement results showed that increased Mg transformed the LaNi_(5)phase in the La_(0.74)Sm_(0.03)Y_(0.23)Ni_(4.32)Al_(0.04)precursor alloy into a superlattice structure.Scanning electron microscopy(SEM)images showed that Mg was evenly distributed in the alloy bulk.Mg in the superlattice significantly inhibited the phase decomposition of the superlattice structure during the hydrogen absorption/desorption cycles.An A_(2)B_(7)-type La_(0.57)Sm_(0.02)Y_(0.18)Mg_(0.23)Ni_(3.38)Al_(0.03)alloy composed of Gd_(2)Co_(7)and Ce_(2)Ni_(7)phases was successfully synthesized.The pressure-composition isotherm profiles showed that the alloy had a hydrogen storage capacity as high as 1.73 wt%,with good cycling stability.After 50 cycles of hydrogen absorption/desorption,the alloy retained a hydrogen storage capacity of 1.45 wt%,with a capacity retention rate of up to 84.28%.The Mg thermal diffusion process thus provides a new approach for the controlled preparation of La-Mg-Ni-based alloys.展开更多
In this work,a Mg-based composite material with in-situ formed LaH3, Mg2 NiH4-LiBH4 ＋ 20 wt% LaH3,was prepared by ball milling LiBH4 and hydrogenated LaMg2 Ni and Mg2 Ni powder mixture, followed by heat treatment at ...In this work,a Mg-based composite material with in-situ formed LaH3, Mg2 NiH4-LiBH4 ＋ 20 wt% LaH3,was prepared by ball milling LiBH4 and hydrogenated LaMg2 Ni and Mg2 Ni powder mixture, followed by heat treatment at 573 K. The onset dehydrogenation temperature of the composite is reduced by 50 K compared with that of Mg2 NiH4-LiBH4. The LaH3-doped composite shows faster kinetics,absorbing1.43 wt% hydrogen within 100 s at 423 K,which is 6.5 times faster than Mg2 NiH4-LiBH4. Moreover,the composite releases 1.24 wt% hydrogen within 500 s at 573 K,0.69 wt% higher than Mg2 NiH4-LiBH4. The activation energy of the composite is reduced by 8.2 and 80 kJ/mol compared with that of Mg2 NiH4-LiBH4 and commercial MgH2, respectively. The improvement in hydrogen storage properties is attributed to the fact that LaH3 promotes the generation of nano-sized spongy Mg structure, which has good catalytic activity during the subsequent hydrogenation/dehydrogenation process.展开更多
Zr1-xTixCo(x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-tempera...Zr1-xTixCo(x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-temperature(PCT) measurements were carried out using Sievert’s type volumetric apparatus for ZrCo(at 473 K, 573 K and 673 K) and Zr1-xTixCo alloys(at 673 K), respectively. Products after dehydrogenation were characterized by X-ray diffraction(XRD). In addition, the kinetics of Zr1-xTixCo hydride was investigated at 473 K and 673 K,respectively, under hydrogen pressure of 5 MPa. Results showed that Ti substitution for Zr did not change the crystal structure of ZrCo phase.With the increase of temperature from 473 K to 673 K, the extent of disproportionation for ZrCo alloy increased. With Ti content increasing at 673 K, the desorption equilibrium pressure of Zr1-xTixCo-H2 systems elevated and the disproportionation reaction of Zr1-xTixCo alloys was inhibited effectively. Ti substitution decreased the kinetics rate and the effective hydrogen storage capacity of Zr1-xTixCo alloys slightly.Generally speaking, it was found that Zr0.8Ti0.2Co alloy had better anti-disproportionation property with less decrease of effective hydrogen storage capacity which was beneficial to tritium application in the International Thermonuclear Experimental Reactor(ITER).展开更多
In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on ...In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4-MgH2 system was investigated. The experimental results show that LiBH4-MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320℃, and there is a long period of incubation time（around 220 min） for the occurrence of the second decomposition step even at high temperature of 450℃. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150℃, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.展开更多
The Ni−25%X(X=Fe,Co,Cu,molar fraction)solid solutions were prepared and then doped into MgH_(2) through high-energy ball milling.The initial dehydrogenation temperatures of MgH_(2)/Ni−25%X composites are all decreased...The Ni−25%X(X=Fe,Co,Cu,molar fraction)solid solutions were prepared and then doped into MgH_(2) through high-energy ball milling.The initial dehydrogenation temperatures of MgH_(2)/Ni−25%X composites are all decreased by about 90℃relative to the as-milled pristine MgH_(2).The Ni−25%Co solid solution exhibits the most excellent catalytic effect,and the milled MgH_(2)/Ni−25%Co composite can release 5.19 wt.%hydrogen within 10 min at 300℃,while the as-milled pristine MgH_(2) can only release 1.78 wt.%hydrogen.More importantly,the dehydrogenated MgH_(2)/Ni−25%Co composite can absorb 5.39 wt.%hydrogen at 275℃within 3 min.The superior hydrogen sorption kinetics of MgH_(2)/Ni−25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg_(2)Ni(Co)compounds.First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH_(2) systems decrease significantly after doping with transition metal atoms,which interprets well the improved hydrogen sorption properties of MgH_(2) catalyzed by Ni-based solid solutions.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51804116)the Science Technology Talents Lifting Project of Hunan Province(No.2022TJ–N16)+3 种基金the Natural Science Foundation of Hunan Province(No.2024JJ4022,2023JJ30277)the China Postdoctoral Fellowship Program(GZC20233205)the Science and Technology Innovation Program of Hunan Province(No.2022RC3037)the National Innovation and Entrepreneurship Training Program for College Students(No.S202410543035).
文摘Due to their high theoretical capacity and abundant resources,transition metal sulfides are regarded as a prospering alternative to replace the commercial graphite anode in lithium-ion batteries(LIBs),particularly for large-scale energy storage and conversion applications.Nonetheless,low conductivity,easy agglomeration and obvious volume change greatly impede their practical application.In this work,a novel crystalline/non-crystalline carbon co-modified strategy is proposed to fabricate N,S co-doped carbon(NSC)layer wrapped Fe_(0.95)S_(1.05)/carbon nanotubes(CNTs)composite(Fe_(0.95)S_(1.05)/CNTs@NSC)through a simple Fenton reaction followed by a sulfurization process.Systematical characterizations and analyses reveal that this strategy well combines the advantages of crystalline CNTs and non-crystalline NSC,ensuring good conductivity and a high contribution to capacity from the carbon matrix.Meanwhile,the joint encapsulation of Fe_(0.95)S_(1.05)by both CNTs and NSC can significantly mitigate the agglomeration and volume change of Fe_(0.95)S_(1.05)during the continuous charge/discharge process.Benefiting from these advantageous features,the resultant Fe_(0.95)S_(1.05)/CNTs@NSC composite displays much improved cycling stability and rate capability when compared to the counterparts.Clearly,our research offers a distinct and innovative approach to design and construct advanced transition metal sulfides/carbon composite anodes for LIBs.
基金supported by Guangdong Basic and Applied Basic Research Foundation and Project of General Colleges and Universities in Guangdong Province(Nos.2022A1515140002 and 2019GKQNCX127)the Special Innovation Projects of Department of Education’s of Guangdong Provincial(No.2018KTSCX220)+4 种基金the International Cooperation Project of Guangdong Province(No.2019A050510049)the Program for Innovative Research Team of Guangdong Province&Huizhou University(IRTHZU)Indigenous Innovation’s Capability Development Program of Huizhou University(No.HZU202014)the Open Project Program of Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices,Huizhou University(No.EFMD2022015M)the National Natural Science Foundation of China(No.12102068).
文摘High-entropy perovskite ferroelectric materials have attracted significant attention due to their remarkably low remnant polarizations and narrow hysteresis.Thus,these materials offer high-energy density and efficiency,making them suitable for energy storage applications.Despite significant advancements in experimental research,understanding of the properties associated with structure remains incomplete.This study aims to study the structural,electric,and mechanical performances at various scales of the high-entropy(Na_(0.2)Bi_(0.2)Ca_(0.2)Sr_(0.2)Ba_(0.2))TiO_(3)(NBCSB)material.The results of first-principles calculations indicated that the pseudo-intralayer distortion was obviously smaller compared to the interlayer distortion.Among the various bonds,Bi-O,Ca-O,and Na-O experienced the greatest displacement.Similarly,the hybridization between O 2p and Ti 3d states with Bi 6p states was particularly strong,affecting both the ferroelectric polarization and relaxor behavior.The NBCSB materials produced using a typical solid-state process demonstrated exceptional performance in energy storage with a recoverable density of 1.53 J·cm^(-3)and a high efficiency of 89%when subjected to a small electric field of 120 kV·cm^(-1).In addition,these ceramics displayed a remarkable hardness of around 7.23 GPa.NBCSB ceramics exhibited exceptional relaxation characteristics with minimal hysteresis and low remanent polarization due to its nanoscale high dynamic polarization configuration with diverse symmetries(rhombohedral,tetragonal,and cubic)resulting from randomly dispersed A-site ions.The excellent mechanical property is related to the dislocation-blocking effect,solid solution strengthening effect,and domain boundary effect.The findings of this study offer a comprehensive and novel perspective on A-site disordered high-entropy relaxor ferroelectric ceramics.
基金Project supported by the National Natural Science Foundation of China(51962028,51961032,52061036)Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(NJYT23007,NJYT23005,NJYT22064)+1 种基金Natural Science Foundation of Inner Mongolia(2022LHMS05021,2022MS05018)Basic Research Funds for Universities Directly Under the Inner Mongolia Autonomous Region(2023QNJS033)。
文摘Hydrothermal-sintering method was employed to obtain pure and Li,Co,Mn,Cu and Zn doped La_(2)Ti_(2)O_(7) solid solutions.The substitution sites of doping ions are discussed.X-ray diffraction(XRD)results indicate that the doped ions were incorporated into the lattice of La_(2)Ti_(2)O_(7) successfully.Transmission electron microscopy(TEM)measurements prove that the doped ions with smaller radius induce the contraction of lattice.The re sults of UV and photo luminescence(PL)tests show that the doped ions cause the red-shift of band gap energies and enhance the concentrations of oxygen vacancies and defects.The electrochemical hydrogen storage properties of the samples were measured at 303 and 333 K,respectively.The discharge capacities of the doped samples keep growing by increasing the cycle number at 333 K.Meanwhile,the doped samples possess better kinetic performances than the pure La_(2)Ti_(2)O_(7).Among the samples,the Mn,Co and Li ions doped samples exhibit better electrochemical hydrogen storage properties.The hydrogen storage properties are closely related with the characteristics of doped ions,crystallite sizes,the content of the oxygen vacancies and defects in the lattice of La_(2)Ti_(2)O_(7).
基金supported by the Key-Area Research and Development Program of Guangdong Province(No.2023B0909060001)the National Natural Science Foundation of China(No.52271213)。
文摘This review details the advancement in the development of V–Ti-based hydrogen storage materials for using in metal hydride(MH)tanks to supply hydrogen to fuel cells at relatively ambient temperatures and pressures.V–Tibased solid solution alloys are excellent hydrogen storage materials among many metal hydrides due to their high reversible hydrogen storage capacity which is over 2 wt%at ambient temperature.The preparation methods,structure characteristics,improvement methods of hydrogen storage performance,and attenuation mechanism are systematically summarized and discussed.The relationships between hydrogen storage properties and alloy compositions as well as phase structures are discussed emphatically.For large-scale applications on MH tanks,it is necessary to develop low-cost and high-performance V–Ti-based solid solution alloys with high reversible hydrogen storage capacity,good cyclic durability,and excellent activation performance.
基金supported by the National Natural Science Foundation of PR China(Nos.52071287,52125104 and 52072342)Natural Science Foundation of Zhejiang Province,PR China(No.LZ23E010002).
文摘MgH_(2)is a promising solid-state hydrogen storage material.However,its high thermodynamics and sluggish kinetics hinder its practical application.Catalytic strategy is effective in improving its kinetic performance.Nevertheless,the highly efficient catalysts or additives are normally of low-yield in fabrication with high cost.In this work,a novel structural LaVO_(4)fabricated by a low-cost method of spraying dry followed by a calcination is used as a catalytic additive for the hydrogen storage of MgH_(2).With an optimized addition of LaVO_(4),the overall hydrogen storage performances of MgH_(2)are significantly improved.An onset dehydrogenation temperature of only 183℃is obtained after an initial activation of dehydrogenation and hydrogenation.The system can desorb 5.7 wt%H_(2)at 250℃within 10 min and maintains a dehydrogenation capacity of 5.0 wt%H_(2)after 50 cycles.It is found that LaVO_(4)is transferred to lanthanum hydride and metallic vanadium in the initial dehydrogenation process,the former acts as a highly effective catalyst for the hydrogen storage of MgH_(2)and the latter undergoes reversible hydrogenation and dehydrogenation in the subsequent cycles.The structural design of the catalyst and its scalable fabrication are highly valuable in realizing the practical application of catalytic strategy for the hydrogen storage of MgH_(2).
基金国家自然科学基金(12104188,12474095 and 52402323)开放基金(2023KF03,KYCX24-4102)。
文摘Introduction Pure NBT exhibits the frequency-dependent Curie temperature,indicating that its dielectric properties are affected by temperature,measurement frequency,and material processing condition.To enhance the dielectric and relaxor properties of NBT,various dopants such as Sr,K,Li and Bi are incorporated into the NBT structure.These modifications significantly alter the dielectric constant and relaxation behavior,demonstrating a dominant influence of dopant on the material properties.Among these,the solid solution of BaTiO_(3)(BT)with NBT is widely investigated due to its ability to stabilize the perovskite structure and improve dielectric performance.However,the temperature-dependent stability of dielectric properties remains a critical challenge for high-temperature applications.In this study,(1-x)(0.75Na_(0.5)Bi_(0.5)TiO_(3)-0.25BaTiO_(3))-xBaZrO_(3)(NBT-BT-xBZ,x=0,0.08,0.14,and 0.20)ceramics were prepared by a solid-state reaction method.The effect of BaZrO_(3)(BZ)addition on the structural,dielectric,and energy storage properties was systematically investigated.In addition,the phase transition and relaxation behaviors were also analyzed based on the modified Curie-Weiss law,Vogel-Fulcher relation,and Lorentz-type empirical law.Methods The starting materials were powders of high purity Na_(2)CO_(3),Bi_(2)O_(3),TiO_(2),BaCO_(3),and ZrO_(2).The powders were weighed according to a stoichiometric ratio(with 1%excess of Na and Bi)and ground with ethanol in a ball mill at 300 r/min for more than 12 h,and the weight ratio of raw material to ethanol and zirconium balls was 1:1:2.The dried material was heat-treated at 850℃ for 2 h to promote the formation of NBT-BT-BZ.After further grinding for 12 h,the samples were mixed with a small amount of polyvinyl alcohol(PVA).The samples were sintered in air at 1150℃for 2 h and cooled to room temperature.The phase composition of the ceramic samples was determined by an model D8 ADVANDCE X-ray diffractometer(D8 ADVANDCEXRD,Bruker AXS Ltd.,Germany)with Cu target Kαrays,at X-ray wavelengthλof 1.5406Å,2θin the range of 10°to 80°,applied voltage of 40 kV,and a current of 500 mA.A silver paste was coated on the two surfaces as electrodes and heat-treated at 700℃ for 10 min.The dielectric properties of the ceramic samples were determined at different frequencies by a model DMS-1000 high-temperature dielectric temperature spectroscope(BALAB Tech.Co.,China)with at a ramp rate of 3(°)/min in a temperature range from room temperature to 450℃.The overdamped(200Ω)discharge tests for bulk ceramic samples were performed by a model CFD-005 discharge tester(Gogo(GG)Instruments Technology,China)).Results and discussion The XRD patterns indicate that all the ceramic samples have a perovskite structure without any detectable secondary phase,proving that zirconium ions can completely enter the lattice and form a solid solution.Based on the locally magnified XRD peaks,the XRD peak shape shifts towards lower angles as a whole as the BZ content increases.This indicates that the overall volume of the crystal cell shows an expansion as the Zr ions replace Ti ions due to different ionic radii of Zr and Ti ions.The SEM images show that the grain size gradually increases with increasing the BZ content.The addition of BZ promotes the grain growth.However,this gradually slows down with the increase of content up to x of 0.20.The limited grain size variation appears in the latter two samples.All the samples show a relatively dense morphology.The Curie temperature of the NBT-0.25BT ceramic samples is 256℃,which is similar to the reported results.The Curie temperature decreases gradually with the increase of BZ additive,and the dielectric temperature spectrum flattens out,indicating that the enhanced structural and temperature stability of the NBT-BT-BZ ceramics.The maximum values of all dielectric constants correspond to temperatures that increase with frequency,indicating a dielectric relaxor behavior.A frequency dispersion is accompanied at near the Curie temperature,which can be ascribed to the thermal evolution of the tetragonal polar nanoregions(PNRs)and the mixing effect of the transition from tripartite to tetragonal PNRs.Theγvalues obtained from the experimental data at 100 kHz are 1.79,1.83,1.89,and 1.92 for NBT-BT,NBT-BT-0.08BZ,NBT-BT-0.14BZ,and NBT-BT-0.20BZ,respectively.Theγvalue increases gradually with the addition of the BZ content,showing an enhanced relaxation of the NBT-BT-BZ ceramics.The comparison of discharge current curves and energy density of all the ceramics indicate that the addition of BZ significantly improves the discharge current and energy storage performance.A high discharging energy density(Wd)of 1.6 J·cm^(-3) with a fast discharging speed(τ0.9)of 75 ns is obtained for the ceramic samples with x of 0.14.This can be attributed to an increased relaxation as the BZ content increases.Conclusions NBT-BT-BZ ceramics were prepared by a solid-state reaction method.The XRD patterns revealed a phase transition from a tetragonal phase to a pseudocubic phase as the BZ content increased.The dielectric relaxation behavior of the ceramics could be described by three empirical laws(i.e.,modified Curie-Weiss law,Vogel-Fulcher relation and Lorentz-type empirical law).The dielectric relaxation followed the modified Curie-Weiss law and the Vogel-Fulcher relationship.The parametersγand Ea,which were obtained to evaluate the relaxation behavior,increased at a higher BZ content.The Lorentz-type relationship effectively described the temperature dependence of the dielectric constant on both the low-and high-temperature sides within a specific temperature range for all the ceramics.
基金Project(51201058)supported by the National Natural Science Foundation of ChinaProjects(E2010000941,E2014209009)supported by Hebei Provincial Natural Science Foundation of China
文摘ZrMn2 alloy was electro-synthesized directly from cathode pellets compacted with powdered mixture of MnO2 and ZrO2 in molten calcium chloride. Sintering temperature, cell voltage and electrolysis time were the dominant factors that affected the characteristics of the final product. The results confirmed the formation of pure ZrMn2 alloy through the electro-deoxidation of the mixed oxide pellets at 3.1 V for 12 h in 900 °C CaCl2 melt. The X-ray diffraction（XRD） and cyclic voltammetry analysis suggested that the electro-deoxidation proceeded from the reduction of manganese oxides to Mn, followed by ZrO2 or CaZrO3 reduction on the pre-formed Mn to ZrMn2 alloy. The cyclic voltammetry measurements using powder microelectrode showed that the prepared ZrMn2 alloy has a good electrochemical hydrogen storage property.
基金financially supported by the Natural Science Foundation of Zhejiang Province(No.LQ24E010003)the Baima Lake Laboratory Joint Funds of the Zhejiang Provincial Natural Science Foundation of China(Nos.LBMHY24E060004,LBMHY24E060005)
文摘MgH_(2)is a promising solid-state hydrogen storage material;one of the limitations of its scale-application is the slow rate of hydrogen uptake and release.The addition of catalyst to improve the kinetics of MgH_(2)has achieved remarkable results.However,these studies require high-speed ball milling(400-500 rpm)to achieve the combination of MgH_(2)and catalyst,and such harsh processing conditions are difficult to achieve in industrial production.In this work,the catalyst and MgH_(2)were efficiently combined at lower milling speed(300 rpm)by introducing tetrahydrofuran C4H8O(THF)as an auxiliary agent.Moreover,milling with THF promotes the nanocrystallization of MgH_(2),which further improves its performance.Results show that THF-assisted MgH_(2)absorbed 6.1 wt%at 90℃and desorbed 6.1 wt%at 275℃,while the MgH_(2)milling under the same speed without THF cannot absorb hydrogen and only desorbed 3.3 wt%.It reveals that the synergistic effect produced by nano-crystallization and nano-hydrogen pump is the key mechanism of improving the performance of MgH_(2)after introducing THF.This work proposes a novel synergistic strategy for modifying MgH_(2),offering practical insights for enhancing its hydrogen storage performance under low-speed ball milling.
基金supported by the National Key R&D Program of China(2022YFB3807700)the National Natural Science Foundation of China(52072217,22179071,51772169,and 52104313)+3 种基金the Hubei Provincial Natural Science Foundation of China(2023AFB618 and 2024AFB993)the Hubei Natural Science Foundation Innovation Group Project(2022CFA020)the Joint Funds of the Hubei Natural Science Foundation Innovation and Development(2022CFD034)the Major Technological Innovation Project of Hubei Science and Technology Department(2019AAA164)。
文摘Black phosphorus(BP)is recognized as a promising anode for sodium-ion batteries(SIBs)due to its high safety and theoretical capacity.However,traditional ball milling methodologies for fabricating BP composite anodes have not satisfactorily addressed the challenges of poor rate performance and short cycle life.To fill this scientific gap,we herein pioneer incorporating the sodium fast ionic conductorβ"-Al_(2)O_(3)into ball-milled BP with carbon,which facilitates the formation of three-dimensional mass transfer channels in the resulting composite.To stabilize these channels,we develop a novel and environmentally friendly functional binder that outperforms traditional binders in thermal stability,wettability,and mechanical properties.The newly established binder is capable of remarkably mitigating volume expansion and interfacial side reactions in the BP/β"-Al_(2)O_(3)/C composite anode.Additionally,we identify synergistic effects of the binder interacting with the BP/β"-Al_(2)O_(3)/C composite during cycling,characterized by the in-situ formation of P-O-C bonds,which is the first instance of a strong,durable chemical bond between the binder and the active material to the best of our knowledge.These advancements allow the composite electrode to exhibit exceptional sodium storage,including high initial Coulombic efficiency and long-term cycling stability,which surpasses most previous phosphorus-based anodes fabricated via traditional approaches.Notably,when paired with a Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_7(NFPP)cathode,the full cell exhibits unexpectedly high energy and power densities,highlighting the BP potential in SIBs.The findings presented in the present work contribute to the promotion of economical and efficient applications of phosphorus-based anode materials.
基金supported by the National Natural Science Foundation of China(51272173,51002188)the National Basic Research Program of China(2010CB934703)Tianjin Municipal Science and Technology Commission(12ZCZDGX00800)
文摘Three types of carbon nano-onions（CNOs） including Ni@CNOs.Fe3C@CNOs and Fe0.64Ni0.36@CNOs nanoparticles have been synthesized by catalytic decomposition of methane at 850 ℃ using nickel,iron and iron-nickel alloy catalysts.Comparative and systematic studies have been carried out on the morphology,structural characteristics and graphitic crystallinity of these CNOs products.Furthermore,the electrochemical hydrogen storage properties of three types of CNOs have been investigated.Measurements show that the Ni@CNOs have the highest discharge capacity of 387.2 mAh/g,coiTesponding to a hydrogen storage of 1.42%.This comparison study shows the advantages of each catalyst in the growth of CNOs.enabling the controllable synthesis and tuning the properties of CNOs by mediating different metals and their alloy for using in the fuel cell system.
基金This research was financially supported by the State Key Project for Fundamental Research (G2 000026406).]
文摘The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results stow that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in (lie alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.
文摘A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T≤623 K) for hydriding and Igp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-a)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31kJ/(mol.H2) and 59.9±2.99kJ/(mol.H2)respectively.
基金Project supported by National Natural Science Foundation of China (50861003, 51071054)the Natural Science Foundation of Guangxi (2010GXNSFD013004, 2011GXNSFA018034)
文摘The La0.55Pr0.05Nd0.15Mg0.25Ni3.5（Co0.5Al0.5）x（x=0.0, 0.1, 0.3, 0.5） alloys were prepared by magnetic levitation melting under an Ar atmosphere, and the effects of Co and Al on the hydrogen storage and electrochemical properties were systematically investigated by pressure composition isotherms, cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy testing. The results showed that the alloy phases were mainly consisted of （La,Pr）（Ni,Co）5, LaMg2Ni9, （La,Nd）2Ni7 and LaNi3 phases, and the cell volumes of （La,Pr）（Ni,Co）5, LaMg2Ni9, （La,Nd）2Ni7 and LaNi3 phases expanded with Co and Al element added. The hydrogen storage capacity initially increased from 1.36 （x=0） to 1.47 wt.% （x=0.3） and then decreased to 1.22 wt.% （x=0.5）. The discharge capacity retention and cycle stability of the alloy electrodes were improved with the increase of Co and Al contents. The La0.55Pr0.05Nd0.15Mg0.25Ni3.5（Co0.5Al0.5）0.3 alloy electrode possessed better electrochemical kinetic characteristic.
基金supported by National Natural Science Foundation of China (50861003,51071054)Natural Science Foundation of Guangxi(2010GXNSFD013004,2012GXNSFBA053149)+1 种基金the Foundation of Key Laboratory of National Education Ministry for Nonferrous Metals and Materials Processing Technology (GXKFJ09-15)the Guangxi University Program for Science and Technology Research (XBZ110379)
文摘The present study dealt with investigations on the effects of annealing on the hydrogen storage properties of La 1.6 Ti 0.4 MgNi 9 alloys.The experimental alloys were prepared by magnetic levitation melting followed by annealing treatment.For La 1.6 Ti 0.4 MgNi 9 alloys,LaNi 5,LaNi 3 and LaMg 2 Ni 9 were the main phases,Ti 2 Ni phase appeared at 900℃.Annealing not only enhanced the maximum and effective hydrogen storage capacity,improved the hydrogen absorption/desorption kinetics,but also increased the discharge capacity.The cyclic stability had been improved markedly by annealing,e.g.,when the discharge capacity reduced to 60% of maximum discharge capacity,the charge/discharge cycles increased from 66（as-cast） to 89（annealed at 800℃） and 127 times（annealed at 900℃）.La 1.6 Ti 0.4 MgNi 9 alloy annealed at 900℃ exhibited better electrochemical properties compared to the other two alloy electrodes.
文摘The hydriding and dehydriding behaviors of tetrahydrofuran modified Mg,its electronic struc- ture,crystal structure,micro-morphology as well as its stability have been investigated.The modifield Mg absorbs 3.5 wt-％ hydrogen at 643 K in 3.5 MPa H_2,its hydride gives off 3.2 wt-％ hydrogen at 643 K in a vaccum of 1.3 Pa after 20 cycles of hydriding and dehydriding. Tetrahydrofuran alters the electronic structure of Mg but keeps its crystal strueture unchanged.In hydriding products,a new hydride phase is found in addition to the known MgH_2 phase.The hydride formed from Mg is polv-erystalline.The wide-spreading slip bands and twins within crystals indicate that the transformation during absorption of hydrogen causes serious lattice distortions.
基金financially supported by the National Key Research and Development Program of China(2022YFB3803804)the National Natural Science Foundation of China(Nos.51971197,52071281 and 52201282)+3 种基金Basic Innovation Research Project in Yanshan University(No.2022LGZD004)China Postdoctoral Science Foundation(2023M742945)Postdoctoral research project of Hebei Province(B2023003023)Subsidy for Hebei Key Laboratory of Applied Chemistry after Operation Performance(No.22567616H)。
文摘A novel approach based on thermal diffusion was used to achieve controllable Mg content in A_(2)B_(7)-type La-Mg-Ni-based alloys.The formation mechanism of the A_(2)B_(7)-type phase as a result of the thermal diffusion process and the effect of Mg content on hydrogen storage performance were investigated.X-ray diffraction(XRD)patterns and Rietveld refinement results showed that increased Mg transformed the LaNi_(5)phase in the La_(0.74)Sm_(0.03)Y_(0.23)Ni_(4.32)Al_(0.04)precursor alloy into a superlattice structure.Scanning electron microscopy(SEM)images showed that Mg was evenly distributed in the alloy bulk.Mg in the superlattice significantly inhibited the phase decomposition of the superlattice structure during the hydrogen absorption/desorption cycles.An A_(2)B_(7)-type La_(0.57)Sm_(0.02)Y_(0.18)Mg_(0.23)Ni_(3.38)Al_(0.03)alloy composed of Gd_(2)Co_(7)and Ce_(2)Ni_(7)phases was successfully synthesized.The pressure-composition isotherm profiles showed that the alloy had a hydrogen storage capacity as high as 1.73 wt%,with good cycling stability.After 50 cycles of hydrogen absorption/desorption,the alloy retained a hydrogen storage capacity of 1.45 wt%,with a capacity retention rate of up to 84.28%.The Mg thermal diffusion process thus provides a new approach for the controlled preparation of La-Mg-Ni-based alloys.
基金supported by the National Natural Science Foundation of China(51771164,51571173)China Postdoctoral Science Foundation(2016M601281)Scientific Research Projects in Colleges and Universities in Hebei Province,China(ZD2014004,QN2016002)
文摘In this work,a Mg-based composite material with in-situ formed LaH3, Mg2 NiH4-LiBH4 ＋ 20 wt% LaH3,was prepared by ball milling LiBH4 and hydrogenated LaMg2 Ni and Mg2 Ni powder mixture, followed by heat treatment at 573 K. The onset dehydrogenation temperature of the composite is reduced by 50 K compared with that of Mg2 NiH4-LiBH4. The LaH3-doped composite shows faster kinetics,absorbing1.43 wt% hydrogen within 100 s at 423 K,which is 6.5 times faster than Mg2 NiH4-LiBH4. Moreover,the composite releases 1.24 wt% hydrogen within 500 s at 573 K,0.69 wt% higher than Mg2 NiH4-LiBH4. The activation energy of the composite is reduced by 8.2 and 80 kJ/mol compared with that of Mg2 NiH4-LiBH4 and commercial MgH2, respectively. The improvement in hydrogen storage properties is attributed to the fact that LaH3 promotes the generation of nano-sized spongy Mg structure, which has good catalytic activity during the subsequent hydrogenation/dehydrogenation process.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Grant No.2011GB111003)the National HighTech Research and Development Program of China(Grant No.2011AA03A408)
文摘Zr1-xTixCo(x = 0, 0.1, 0.2, 0.3) alloys were prepared by arc-melting method and the effect of Ti substitution on hydrogen storage properties was studied systematically. Hydrogen desorption pressure-composition-temperature(PCT) measurements were carried out using Sievert’s type volumetric apparatus for ZrCo(at 473 K, 573 K and 673 K) and Zr1-xTixCo alloys(at 673 K), respectively. Products after dehydrogenation were characterized by X-ray diffraction(XRD). In addition, the kinetics of Zr1-xTixCo hydride was investigated at 473 K and 673 K,respectively, under hydrogen pressure of 5 MPa. Results showed that Ti substitution for Zr did not change the crystal structure of ZrCo phase.With the increase of temperature from 473 K to 673 K, the extent of disproportionation for ZrCo alloy increased. With Ti content increasing at 673 K, the desorption equilibrium pressure of Zr1-xTixCo-H2 systems elevated and the disproportionation reaction of Zr1-xTixCo alloys was inhibited effectively. Ti substitution decreased the kinetics rate and the effective hydrogen storage capacity of Zr1-xTixCo alloys slightly.Generally speaking, it was found that Zr0.8Ti0.2Co alloy had better anti-disproportionation property with less decrease of effective hydrogen storage capacity which was beneficial to tritium application in the International Thermonuclear Experimental Reactor(ITER).
基金financially supported by the National Natural Science Foundation of China(Nos.51471149 and 51171168)the Public Project of Zhejiang Province(No.2015C31029)
文摘In order to improve the hydrogen storage properties of LiBH4-MgH2 composite, two different kinds of Nb-based catalysts, NbC and NbF5, were added to LiBH4-MgH2 composite by ball milling, and the effect of catalysts on hydrogen storage properties of the modified LiBH4-MgH2 system was investigated. The experimental results show that LiBH4-MgH2 composite is a two-step dehydrogenation process, and Nb-based compounds can remarkably enhance its dehydrogenation kinetics. For the composite without addition of catalysts, the starting decomposition temperature for the first dehydrogenation step is around 320℃, and there is a long period of incubation time（around 220 min） for the occurrence of the second decomposition step even at high temperature of 450℃. It needs more than 10 h to complete the decomposition process and release around 9 wt% H2. After addition of 5 mol% NbF5, the starting decomposition temperature for the first dehydrogenation step is around 150℃, there is no incubation time for the second decomposition step, and it takes around 40 min to complete the second step and reaches a total dehydrogenation capacity of 9.5 wt%. NbF5 has better catalytic effect than NbC. Based on the hydrogenation/dehydrogenation behaviors and structural variation, the mechanism of catalytic effect was discussed.
基金the National Natural Science Foundation of China(Nos.51874049,51904036)the Science Research Project of Hunan Province Office of Education,China(No.20A024)+2 种基金the Changsha Science and Technology Program Project(No.kq1907092)the Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation,China(No.2019CL03)the Research and Innovation Project of Graduate Students in Changsha University of Science and Technology,China(No.CX2020SS35).
文摘The Ni−25%X(X=Fe,Co,Cu,molar fraction)solid solutions were prepared and then doped into MgH_(2) through high-energy ball milling.The initial dehydrogenation temperatures of MgH_(2)/Ni−25%X composites are all decreased by about 90℃relative to the as-milled pristine MgH_(2).The Ni−25%Co solid solution exhibits the most excellent catalytic effect,and the milled MgH_(2)/Ni−25%Co composite can release 5.19 wt.%hydrogen within 10 min at 300℃,while the as-milled pristine MgH_(2) can only release 1.78 wt.%hydrogen.More importantly,the dehydrogenated MgH_(2)/Ni−25%Co composite can absorb 5.39 wt.%hydrogen at 275℃within 3 min.The superior hydrogen sorption kinetics of MgH_(2)/Ni−25%Co can be ascribed to the actual catalytic effect of in-situ formed Mg_(2)Ni(Co)compounds.First-principles calculations show that the hydrogen absorption/desorption energy barriers of Mg/MgH_(2) systems decrease significantly after doping with transition metal atoms,which interprets well the improved hydrogen sorption properties of MgH_(2) catalyzed by Ni-based solid solutions.
