After being activated,TiFe alloys are widely concerned for their high hydrogen storage density due to their large reversible absorption and desorption capacity of hydrogen at room temperature,low price,abundant resour...After being activated,TiFe alloys are widely concerned for their high hydrogen storage density due to their large reversible absorption and desorption capacity of hydrogen at room temperature,low price,abundant resources,moderate hydride decomposition pressure,and good hydrogen absorption and desorption kinetic performance.Meanwhile,TiFe alloys can be used as anode materials for secondary batteries,catalysts for hydrogenation,and storage media for thermal,solar,and wind energy,which has wide industrial application prospects.However,TiFe alloys have disadvantages such as difficult activation,easy toxicity,and large hysteresis.This review introduces the current research status and performance characteristics of TiFe-based hydrogen storage alloys,the phase structure,hydride phase structure,kinetic and thermodynamic models of TiFe alloys,as well as the application prospects of TiFe-based hydrogen storage alloys in practical production and the ways to improve their hydrogen storage performance,and presents the views on the future research priorities and development directions of TiFe-based hydrogen storage alloys.展开更多
Ti–Mn-based hydrogen storage alloys are considered to be one of the most promising hydrogen storage alloys for proton exchange membrane fuel cell applications,because of their good hydrogen absorption and desorption ...Ti–Mn-based hydrogen storage alloys are considered to be one of the most promising hydrogen storage alloys for proton exchange membrane fuel cell applications,because of their good hydrogen absorption and desorption kinetics,low price,good activation performance,possession of high electrochemical capacity,and good cycling performance.The structure,performance characteristics,crystal structure of hydrides,development and application status of Ti–Mn-based hydrogen storage alloys were reviewed,and the methods to improve Ti–Mn-based hydrogen storage alloys were discussed:optimization of the preparation process,element substitution,and surface treatment.(1)In the study of the alloy preparation process,it was found that the use of the annealing process can significantly improve the high rate discharge performance,and cycling stability performance,increasing the maximum discharge capacity of the alloy electrode.In addition,using vacuum plasma spraying to prepare the electrode has better cycling stability and kinetic performance.(2)In element substitution,the effects of using Zr elements to partially replace Ti and Mn with Cr,V,Mo,and Fe on the hydrogen storage properties of Ti–Mn-based alloys were investigated.(3)In the study of surface treatment,palladium was plated on the surface of TiMn_(1.5) alloy by chemical deposition,and the strong affinity of palladium for hydrogen accelerated the cleavage of hydrogen molecules,which significantly improved the hydrogen absorption kinetics of TiMn_(1.5) alloy.Meanwhile,a new binary alloy system was formed by adding TiMn_(2) to MgH_(2),and it was shown that the addition of TiMn_(2) significantly improved the hydrogen absorption/desorption kinetics of the MgH_(2) alloy.Finally,the prospect of the application of Ti–Mn-based hydrogen storage alloys is presented,and the insight of further development of the alloy is offered.展开更多
To address the challenges posed by high reaction temperatures and the slow kinetics of Mg-based alloys with high hydrogen storage density,Mg−RE−TM(RE=rare earth,TM=metallic element)alloys have been extensively researc...To address the challenges posed by high reaction temperatures and the slow kinetics of Mg-based alloys with high hydrogen storage density,Mg−RE−TM(RE=rare earth,TM=metallic element)alloys have been extensively researched and hold great promise.In this study,a series of Mg−RE−TM based Mg_(90)Y_(2)Ce_(2)Ni_(3)Al_(3-x)Sc_(x)(x=0,0.3,0.6,0.9,1.2)alloys were prepared.The addition of Sc element has been found to enhance the activation and kinetic properties of the alloy.Compared with the significant differences in the first four dehydrogenation curves of the Sc0 sample,the first activated dehydrogenation curve of the Sc1.2 alloy overlaps with the fully activated dehydrogenation curve.The dehydrogenation activation energy decreased from 96.56 kJ/mol in the Sc0 alloy to 63.69 kJ/mol in the Sc0.9 alloy.Through analysis of the microstructure,phase composition,and hydrogen absorption and desorption kinetics of the alloy,the mechanisms for improving the hydrogen storage properties of the alloy were elucidated.The nucleation-growth-impingement Avrami model was employed to accurately simulate the hydrogen storage kinetics.The results showed that stage II was prolonged and accelerated at high temperature,and the growth rate and hydrogen storage of stage I were increased at low temperature in hydrogen absorption.Microstructure analysis revealed the presence of Mg,CeMg_(12),Mg_(47)Y,and YNi_(2)Al_(3) phases in the Sc0 sample.Upon the addition of Sc element,a new phase,ScNiAl,was formed,and the coarse grain size of the main phase was significantly refined.This refinement provides faster diffusion channels for hydrogen atoms,accelerating the phase transition between Mg alloys and hydrides.The microstructure changes explain the improved activation properties,effective hydrogen absorption and desorption capacity,and kinetic properties of the Mg-based samples.展开更多
Rare earth(RE)elements have been successfully utilized in solid-state hydrogen storage as hydrogen-absorbing elements with excellent hydrogen storage properties in terms of safety and efficiency.RE-Mg-based hydrogen s...Rare earth(RE)elements have been successfully utilized in solid-state hydrogen storage as hydrogen-absorbing elements with excellent hydrogen storage properties in terms of safety and efficiency.RE-Mg-based hydrogen storage materials with high magnesium content are considered to be one of the most promising hydrogen storage materials for application due to their high mass/volume hydrogen storage density,moderate required hydrogen pressure,good reversibility,non-toxicity,and harmlessness.Furthermore,RE-Mg-based materials with low magnesium content and superlattice structure show great potential for application in the field of solid-state hydrogen storage.They are also widely used as anode materials for nickel-metal hydride batteries.In this paper,we comprehensively summarized and evaluated the organization and hydrogen storage properties of different RE-Mg system alloys(Mg-RE,Mg-RE-TM(TM=transition metals),and superlattice-type RE-Mg-TM)and the catalytic effect and mechanisms of catalysts on RE-Mg system alloys.The interactions between the types of RE elements,the contents of RE elements,the crystal structures,and the catalysts with the microstructure morphology and hydrogen storage properties of RE-Mg-based hydrogen storage alloys were established.The intrinsic mechanisms between microstructure morphology,phase structure,phase composition,and hydrogen storage properties of alloys with different RE-Mg-based systems were elucidated.By comparing the differences and characteristics between the organizational structures and hydrogen storage properties of different RE-Mg systems,a feasible idea and solution for the rational design and development of RE-Mg-based alloys with high hydrogen storage capacity,low cost,and fast hydrogen absorption and desorption kinetics was proposed.展开更多
The La_(1.7)Pr_(0.3)Mg_(16)Ni hydrogen storage alloy was prepared by medium-frequency induction melting,and then the composite hydrogen storage alloy powder of La_(1.7)Pr_(0.3)Mg_(16)Ni+x wt.%(x=0,2,4,and 6)graphene w...The La_(1.7)Pr_(0.3)Mg_(16)Ni hydrogen storage alloy was prepared by medium-frequency induction melting,and then the composite hydrogen storage alloy powder of La_(1.7)Pr_(0.3)Mg_(16)Ni+x wt.%(x=0,2,4,and 6)graphene was prepared by ball milling for 10 h.The effect of the addition of graphene on the activation and hydrogen de/absorption properties of La_(1.7)Pr_(0.3)Mg_(16)Ni alloy was studied.The result demonstrated that these composite alloys were composed of La_(2)Mg_(17),La_(2)Ni_(3),and Mg_(2)Ni phases.After saturated hydrogen absorption,it was composed of LaH_(3),Mg_(2)NiH_(4),and MgH_(2)phases,while during the dehydrogenation process,it was composed of LaH_(3),Mg,and Mg_(2)Ni phases.The addition of graphene can help get a more homogeneous granule after ball milling and accelerate the first activation of dehydrogenation/hydrogen absorption.The hydrogen release activation energy of the alloys first decreases and then increases as the graphene content increases from x=0 wt.%to x=6 wt.%.The minimum activation energy of the composite hydrogen storage alloy is 51.22 kJ mol^(-1) when x=4 wt.%.展开更多
Magnesium and magnesium-based alloy hydrides remain attractive hydrogen storage materials owing to high hydrogen capacity and rich reserves in the earth＇s crust. A high stability of hydride and sluggish hydriding/deh...Magnesium and magnesium-based alloy hydrides remain attractive hydrogen storage materials owing to high hydrogen capacity and rich reserves in the earth＇s crust. A high stability of hydride and sluggish hydriding/dehydriding kinetics at practical temperatures for the materials drove researchers into alloying with other elements, using different preparation techniques, using catalyst and thin film hydride to improve the hydrogen absorption/desorption properties. In this review, the development of these approaches and their effects on the thermodynamic and kinetics properties of magnesium and magnesium-based alloy hydrides were descript in details.展开更多
La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the s...La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.展开更多
The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT cha...The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT characterization methods.The result shows that the activated alloys are composed of Mg/MgH2 and corresponding REH2+x with nanoscale.The REH2+x grain with Ce and La or Nd functional group have lower nucleation potential barriers than CeH2+x grains as the nucleation location,thus improve the hydrogen absorption kinetics of these alloys among which the Mg90Ce5Nd5 alloy can absorb 90%of the hydrogen within 2 min at 320℃.In addition,the Mg90Ce10 alloy has the lowest activation energy with 103.2 kJ mol-1 and the fastest desorption kinetics,which can release 5 wt%of the hydrogen within 20 min at 320℃.This is a correlation with grain size and the in-suit formed CeH2.73/CeO2 interface.Moreover,the co-doping Ce and La or Nd can effectively disorganize the thermodynamic stability of Mg-based hydrogen storage alloys to a certain degree,but the dehydrogenation kinetics of that still is restricted by the recombination energy of hydrogen ions on the surface.展开更多
To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of di...To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.展开更多
The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermod...The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermodynamics of TiFe-type Ti−Fe−Mn-based alloy were investigated.The as-spun alloys hold the TiFe single phase,which transforms to TiFeH_(0.06),TiFeH,and TiFeH_(2) hydrides after hydrogenation.La substitution promotes the formation of micro-defects(such as dislocations and grain boundaries)in the alloys,thus facilitating hydrogen diffusion.In addition,the hydrogen storage kinetics properties are improved after introducing La element.With the rise of La content,the hydrogen storage capacity decreases firstly and then increases,but the absolute value of hydriding enthalpy change(|ΔH|)increases firstly and then reduces.When x=0.01,the maximum value of|ΔH|is obtained to be(25.23±0.50)kJ/mol for hydriding,and the alloy has the maximum hydrogen absorption capacity of(1.80±0.04)wt.%under the conditions of 323 K and 3 MPa.展开更多
La-Mg-Ni-Mn-based AB2-type La（1–x）CexMgNi（3.5）Mn（0.5）（x=0–0.4） alloys were prepared by melt spinning technology. The detections of X-ray diffraction（XRD） and scanning electron microscopy（SEM） indicated t...La-Mg-Ni-Mn-based AB2-type La（1–x）CexMgNi（3.5）Mn（0.5）（x=0–0.4） alloys were prepared by melt spinning technology. The detections of X-ray diffraction（XRD） and scanning electron microscopy（SEM） indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.展开更多
Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydr...Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C(100)~a) and hydrogen absorption saturation ratio(R(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.展开更多
The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 （x = 0, 0.1, 0.2, 0.3, and 0.4） electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the s...The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 （x = 0, 0.1, 0.2, 0.3, and 0.4） electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases： （La,Mg）2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCus-type structure as well as some residual phases of LaNi3 and NdNis. The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.展开更多
La was partially substituted by Ce with the aim of improving the electrochemical hydrogen storage performances ofLa1–xCexMgNi3.5Mn0.5 (x=0, 0.1, 0.2, 0.3, 0.4) alloys, and melt spinning technology was adopted to fabr...La was partially substituted by Ce with the aim of improving the electrochemical hydrogen storage performances ofLa1–xCexMgNi3.5Mn0.5 (x=0, 0.1, 0.2, 0.3, 0.4) alloys, and melt spinning technology was adopted to fabricate the alloys. Theidentification of XRD and SEM reveals that the experimental alloys consist of a major phase LaMgNi4 and a secondary phase LaNi5.The growth of spinning rate results in that the lattice constants and cell volume increase and the grains are markedly refined. Theelectrochemical measurement shows that the as-cast and spun alloys can obtain the maximum discharge capacities just at the firstcycle without any activation needed. With the increase of spinning rate, the discharge capacities of the alloys first increase and thendecline, whereas their cycle stabilities always grow. Moreover, the electrochemical kinetic performances of the alloys first increaseand then decrease with spinning rate growing.展开更多
The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and ...The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.展开更多
Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase st...Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase structure and microstructure of the samples were investigated using X-ray diffraction and scanning electron microscope, respectively. The complex permeability was measured using the impedance analyzer in the range of 1-100 MHz. The results indicate that with increasing Nd^3＋ content, the relative density and lattice parameter a of the sintered samples increase, whereas the real part of permeability （μ′） and the magnetic loss tangent （tan δ） decrease. The substitution of Nd^3＋ for Fe^3＋ forms a secondary phase on the grain boundary of the matrix, which strongly restrains the grain growth of the matrix.展开更多
Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydroge...Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM) and pressure-composition isotherms(PCI) measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases(Ce,Sm)5 Mg41 and the minor phases(Ce,Sm)Mg12.After hydrogen absorption,these phases transform into the MgH2 and(Ce,Sm)H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the(Ce,Sm)H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of(Ce,Sm)H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.展开更多
Nanocrystalline and amorphous LaMg11Ni+x%Ni(x=100,200,mass fraction)alloys were synthesized by mechanicalmilling.The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galv...Nanocrystalline and amorphous LaMg11Ni+x%Ni(x=100,200,mass fraction)alloys were synthesized by mechanicalmilling.The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system.The gaseous hydrogen absorption and desorption properties were investigated by Sievert’s apparatus and differential scanningcalorimeter(DSC)connected with a H2detector.The results indicated that increasing Ni content significantly improves the gaseousand electrochemical hydrogen storage performances of the as-milled alloys.The gaseous hydrogen absorption capacities andabsorption rates of the as-milled alloys have the maximum values with the variation of the milling time.But the hydrogen desorptionkinetics of the alloys always increases with the extending of milling time.In addition,the electrochemical discharge capacity andhigh rate discharge(HRD)ability of the as-milled alloys both increase first and then decrease with milling time prolonging.展开更多
In order to improve the electrochemical cycle stability of the RE–Mg–Ni-based A2B7-type electrode alloys, a small amount of Si has been added into the alloys.The casting and annealing technologies were adopted to fa...In order to improve the electrochemical cycle stability of the RE–Mg–Ni-based A2B7-type electrode alloys, a small amount of Si has been added into the alloys.The casting and annealing technologies were adopted to fabricate the La0.8Mg0.2Ni3.3Co0.2Six(x = 0–0.2) electrode alloys. The impacts of the addition of Si and annealing treatment on the structures and electrochemical performances of the alloys were investigated systematically. The results obtained by XRD and SEM show that all the as-cast and annealed alloys are of a multiphase structure, involving two main phases(La, Mg)2Ni7and La Ni5 as well as a residual phase La Ni3. Both adding Si and the annealing treatment lead to an evident change in the phase abundance and cell parameters of(La, Mg)2Ni7and La Ni5 major phases of the alloy without altering its main phase component. Moreover, the annealing treatment has the composition of the alloy distributed more homogeneously overall and simultaneously causes the grain of the alloy to be coarsened obviously. The electrochemical measurements indicate that adding Si and the annealing treatment give a significant rise to the influence on the electrochemical performances of the alloys. In brief, the cycle stability of the as-cast and annealed alloys evidently increases with the rising of Si content, while their discharge capacities obviously decrease under the same circumstances. Furthermore, the electrochemical kineticproperties of the electrode alloys, including the high rate discharge ability, the limiting current density(IL), hydrogen diffusion coefficient(D), and the charge-transfer resistance, first augment and then decline with the rising of Si content. Similarly, it is found that the above-mentioned electrochemical properties first mount up and then go down with the rising annealing temperature.展开更多
In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology ...In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology was used to fabricate the La_(0.75-x)M_xMg_0.25Ni_3.2Co_0.2Al_0.1 (M = Zr, Pr; x = 0, 0.1) electrode alloys. The influences of the melt spinning and substituting La with M (M = Zr, Pr) on the structures and the electrochemical hydrogen storage characteristics of the alloys were investigated. The analysis of XRD, SEM, and TEM reveals that the as-cast and spun alloys have a multiphase structure composed of two main phases (La, Mg)_2Ni_7 and LaNi_5 as well as a residual phase LaNi_2 . The as-spun (M = Pr) alloy displays an entire nanocrystalline structure, while an amorphous-like structure is detected in the as-spun (M = Zr) alloy, implying that the substitution of Zr for La facilitates the amorphous formation. The electrochemical measurements exhibit that the substitution of Pr for La clearly increases the discharge capacity of the alloys; however, the Zr substitution brings on an adverse impact. Meanwhile, the M (M = Zr, Pr) substitution significantly enhances its cycle stability. The melt spinning exerts an evident effect on the electrochemical performances of the alloys, whose discharge capacity and high rate discharge ability (HRD) first mount up and then fall with the growing spinning rate, whereas their cycle stabilities monotonously augment as the spinning rate increases.展开更多
基金National Natural Science Foundation of China(51761032)Natural Science Foundation of Inner Mongolia,China(No.2019BS05005)Inner Mongolia University of Science and Technology Innovation Fund-(2019QDL-B11).
文摘After being activated,TiFe alloys are widely concerned for their high hydrogen storage density due to their large reversible absorption and desorption capacity of hydrogen at room temperature,low price,abundant resources,moderate hydride decomposition pressure,and good hydrogen absorption and desorption kinetic performance.Meanwhile,TiFe alloys can be used as anode materials for secondary batteries,catalysts for hydrogenation,and storage media for thermal,solar,and wind energy,which has wide industrial application prospects.However,TiFe alloys have disadvantages such as difficult activation,easy toxicity,and large hysteresis.This review introduces the current research status and performance characteristics of TiFe-based hydrogen storage alloys,the phase structure,hydride phase structure,kinetic and thermodynamic models of TiFe alloys,as well as the application prospects of TiFe-based hydrogen storage alloys in practical production and the ways to improve their hydrogen storage performance,and presents the views on the future research priorities and development directions of TiFe-based hydrogen storage alloys.
基金It is sincere thanks to the National Natural Science Foundations of China(Grant.Nos.51761032,51871125 and 51731002)for financial support of the work.
文摘Ti–Mn-based hydrogen storage alloys are considered to be one of the most promising hydrogen storage alloys for proton exchange membrane fuel cell applications,because of their good hydrogen absorption and desorption kinetics,low price,good activation performance,possession of high electrochemical capacity,and good cycling performance.The structure,performance characteristics,crystal structure of hydrides,development and application status of Ti–Mn-based hydrogen storage alloys were reviewed,and the methods to improve Ti–Mn-based hydrogen storage alloys were discussed:optimization of the preparation process,element substitution,and surface treatment.(1)In the study of the alloy preparation process,it was found that the use of the annealing process can significantly improve the high rate discharge performance,and cycling stability performance,increasing the maximum discharge capacity of the alloy electrode.In addition,using vacuum plasma spraying to prepare the electrode has better cycling stability and kinetic performance.(2)In element substitution,the effects of using Zr elements to partially replace Ti and Mn with Cr,V,Mo,and Fe on the hydrogen storage properties of Ti–Mn-based alloys were investigated.(3)In the study of surface treatment,palladium was plated on the surface of TiMn_(1.5) alloy by chemical deposition,and the strong affinity of palladium for hydrogen accelerated the cleavage of hydrogen molecules,which significantly improved the hydrogen absorption kinetics of TiMn_(1.5) alloy.Meanwhile,a new binary alloy system was formed by adding TiMn_(2) to MgH_(2),and it was shown that the addition of TiMn_(2) significantly improved the hydrogen absorption/desorption kinetics of the MgH_(2) alloy.Finally,the prospect of the application of Ti–Mn-based hydrogen storage alloys is presented,and the insight of further development of the alloy is offered.
基金National Natural Science Foundation of China(51871125)the Major Programs of Central Iron and Steel Research Institute(No.23020230ZD)for financial support of the work.
文摘To address the challenges posed by high reaction temperatures and the slow kinetics of Mg-based alloys with high hydrogen storage density,Mg−RE−TM(RE=rare earth,TM=metallic element)alloys have been extensively researched and hold great promise.In this study,a series of Mg−RE−TM based Mg_(90)Y_(2)Ce_(2)Ni_(3)Al_(3-x)Sc_(x)(x=0,0.3,0.6,0.9,1.2)alloys were prepared.The addition of Sc element has been found to enhance the activation and kinetic properties of the alloy.Compared with the significant differences in the first four dehydrogenation curves of the Sc0 sample,the first activated dehydrogenation curve of the Sc1.2 alloy overlaps with the fully activated dehydrogenation curve.The dehydrogenation activation energy decreased from 96.56 kJ/mol in the Sc0 alloy to 63.69 kJ/mol in the Sc0.9 alloy.Through analysis of the microstructure,phase composition,and hydrogen absorption and desorption kinetics of the alloy,the mechanisms for improving the hydrogen storage properties of the alloy were elucidated.The nucleation-growth-impingement Avrami model was employed to accurately simulate the hydrogen storage kinetics.The results showed that stage II was prolonged and accelerated at high temperature,and the growth rate and hydrogen storage of stage I were increased at low temperature in hydrogen absorption.Microstructure analysis revealed the presence of Mg,CeMg_(12),Mg_(47)Y,and YNi_(2)Al_(3) phases in the Sc0 sample.Upon the addition of Sc element,a new phase,ScNiAl,was formed,and the coarse grain size of the main phase was significantly refined.This refinement provides faster diffusion channels for hydrogen atoms,accelerating the phase transition between Mg alloys and hydrides.The microstructure changes explain the improved activation properties,effective hydrogen absorption and desorption capacity,and kinetic properties of the Mg-based samples.
基金supported by the National Natural Science Foundation of China(51871125)the Major Programs of Central Iron and Steel Research Institute(No.23020230ZD).
文摘Rare earth(RE)elements have been successfully utilized in solid-state hydrogen storage as hydrogen-absorbing elements with excellent hydrogen storage properties in terms of safety and efficiency.RE-Mg-based hydrogen storage materials with high magnesium content are considered to be one of the most promising hydrogen storage materials for application due to their high mass/volume hydrogen storage density,moderate required hydrogen pressure,good reversibility,non-toxicity,and harmlessness.Furthermore,RE-Mg-based materials with low magnesium content and superlattice structure show great potential for application in the field of solid-state hydrogen storage.They are also widely used as anode materials for nickel-metal hydride batteries.In this paper,we comprehensively summarized and evaluated the organization and hydrogen storage properties of different RE-Mg system alloys(Mg-RE,Mg-RE-TM(TM=transition metals),and superlattice-type RE-Mg-TM)and the catalytic effect and mechanisms of catalysts on RE-Mg system alloys.The interactions between the types of RE elements,the contents of RE elements,the crystal structures,and the catalysts with the microstructure morphology and hydrogen storage properties of RE-Mg-based hydrogen storage alloys were established.The intrinsic mechanisms between microstructure morphology,phase structure,phase composition,and hydrogen storage properties of alloys with different RE-Mg-based systems were elucidated.By comparing the differences and characteristics between the organizational structures and hydrogen storage properties of different RE-Mg systems,a feasible idea and solution for the rational design and development of RE-Mg-based alloys with high hydrogen storage capacity,low cost,and fast hydrogen absorption and desorption kinetics was proposed.
基金supported by the Inner Mongolia Natural Science Foundation(2021MS05064)China Northern Rare Earth Group High-Tech Co.,Ltd.(Bayan Obo rare earth resources extraction and application research and key technology development,2022151).
文摘The La_(1.7)Pr_(0.3)Mg_(16)Ni hydrogen storage alloy was prepared by medium-frequency induction melting,and then the composite hydrogen storage alloy powder of La_(1.7)Pr_(0.3)Mg_(16)Ni+x wt.%(x=0,2,4,and 6)graphene was prepared by ball milling for 10 h.The effect of the addition of graphene on the activation and hydrogen de/absorption properties of La_(1.7)Pr_(0.3)Mg_(16)Ni alloy was studied.The result demonstrated that these composite alloys were composed of La_(2)Mg_(17),La_(2)Ni_(3),and Mg_(2)Ni phases.After saturated hydrogen absorption,it was composed of LaH_(3),Mg_(2)NiH_(4),and MgH_(2)phases,while during the dehydrogenation process,it was composed of LaH_(3),Mg,and Mg_(2)Ni phases.The addition of graphene can help get a more homogeneous granule after ball milling and accelerate the first activation of dehydrogenation/hydrogen absorption.The hydrogen release activation energy of the alloys first decreases and then increases as the graphene content increases from x=0 wt.%to x=6 wt.%.The minimum activation energy of the composite hydrogen storage alloy is 51.22 kJ mol^(-1) when x=4 wt.%.
基金financially supported by the National Natural Science Foundation of China (Nos. 51161015 and 51371094)
文摘Magnesium and magnesium-based alloy hydrides remain attractive hydrogen storage materials owing to high hydrogen capacity and rich reserves in the earth＇s crust. A high stability of hydride and sluggish hydriding/dehydriding kinetics at practical temperatures for the materials drove researchers into alloying with other elements, using different preparation techniques, using catalyst and thin film hydride to improve the hydrogen absorption/desorption properties. In this review, the development of these approaches and their effects on the thermodynamic and kinetics properties of magnesium and magnesium-based alloy hydrides were descript in details.
基金Project supported by National 863 Program of China (2007AA03Z227, 2007AA03Z230)Natural Science Foundation of Hebei Province (E2010000301)+1 种基金Natural Science Research Planned Project of Hebei University (2009-152)Undergraduate Science and Technology Innovation Project of Hebei University (2010060)
文摘La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.
基金supported financially by the National Natural Science Foundations of China(Nos.51901105,51761032 and 51871125)the Natural Science Foundation of Inner Mongolia,China(No.2019BS05005)the Inner Mongolia University of Science and Technology Innovation Fund(2019QDL-B11)。
文摘The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT characterization methods.The result shows that the activated alloys are composed of Mg/MgH2 and corresponding REH2+x with nanoscale.The REH2+x grain with Ce and La or Nd functional group have lower nucleation potential barriers than CeH2+x grains as the nucleation location,thus improve the hydrogen absorption kinetics of these alloys among which the Mg90Ce5Nd5 alloy can absorb 90%of the hydrogen within 2 min at 320℃.In addition,the Mg90Ce10 alloy has the lowest activation energy with 103.2 kJ mol-1 and the fastest desorption kinetics,which can release 5 wt%of the hydrogen within 20 min at 320℃.This is a correlation with grain size and the in-suit formed CeH2.73/CeO2 interface.Moreover,the co-doping Ce and La or Nd can effectively disorganize the thermodynamic stability of Mg-based hydrogen storage alloys to a certain degree,but the dehydrogenation kinetics of that still is restricted by the recombination energy of hydrogen ions on the surface.
基金Project supported by the National Natural Science Foundation of China(50642033 50701011)+1 种基金Key Technologies R&D Program of Inner Mongolia, China (20050205)Natural Science Foundation of Inner Mongolia, China (200711020703)
文摘To improve the cyclic stability of La-Mg-Ni system alloy, as-cast La0.75Mg0.25Ni3.5Co0.2 alloy was annealed at 1123, 1223, and 1323 K for 10 h in 0.3 MPa argon. The microstructure and electrochemical performance of different annealed alloys were investigated systematically by X-Ray Diffraction （XRD）, Scanning Electron Microscopy （SEM）, X-Ray Photoelectron Spectroscopy （XPS）, and electrochemical experiments. The results obtained by XRD and SEM showed that the as-cast and annealed （1123 K） alloys had multiphase structure containing LaNis, （La, Mg）2（Ni, Co）7 and few LaNi2 phases. When annealing temperatures approached 1223 and 1323 K, LaNi2 phase disappeared. The annealed alloys at 1223 and 1323 K were composed of LaNi5, （La, Mg）2（Ni, Co）7 and （La, Mg）（Ni, Co）3 phases. With increasing annealing temperature, the maximum discharge capacity of the alloy decreased monotonously, but the cyclic stability was improved owing to structure homogeneity and grain growth after annealing, as well as the enhancement of anti-oxidation/corrosion ability and the suppression of pulverization during cycling in KOH electrolyte.
基金financial supports from the Inner Mongolia Natural Science Foundation,China (No.2019BS05005)the Inner Mongolia University of Science and Technology Innovation Fund,China (No.2019QDL-B11)the National Natural Science Foundation of China (Nos.51901105, 51871125, 51761032).
文摘The as-spun Ti_(1−x)La_(x)Fe_(0.8)Mn_(0.2)(x=0,0.01,0.03,0.06,0.09,molar fraction)alloys were prepared by melt spinning.The effects of La substitution for Ti on the microstructure,hydrogen storage kinetics and thermodynamics of TiFe-type Ti−Fe−Mn-based alloy were investigated.The as-spun alloys hold the TiFe single phase,which transforms to TiFeH_(0.06),TiFeH,and TiFeH_(2) hydrides after hydrogenation.La substitution promotes the formation of micro-defects(such as dislocations and grain boundaries)in the alloys,thus facilitating hydrogen diffusion.In addition,the hydrogen storage kinetics properties are improved after introducing La element.With the rise of La content,the hydrogen storage capacity decreases firstly and then increases,but the absolute value of hydriding enthalpy change(|ΔH|)increases firstly and then reduces.When x=0.01,the maximum value of|ΔH|is obtained to be(25.23±0.50)kJ/mol for hydriding,and the alloy has the maximum hydrogen absorption capacity of(1.80±0.04)wt.%under the conditions of 323 K and 3 MPa.
基金Project supported by National Natural Science Foundation of China(51161015,51371094,51471054)
文摘La-Mg-Ni-Mn-based AB2-type La（1–x）CexMgNi（3.5）Mn（0.5）（x=0–0.4） alloys were prepared by melt spinning technology. The detections of X-ray diffraction（XRD） and scanning electron microscopy（SEM） indicated that the experimental alloys consisted of a major phase LaMgNi4 and a secondary phase LaNi5. With spinning rate growing, the abundance of LaMgNi4 phase increased and that of LaNi5 phase decreased. Moreover, with the melt spinning rate increasing, both the lattice constants and cell volumes increased, and further accelerated the grains refinement of the alloys. The electrochemical tests showed that the as-spun alloys possessed excellent capability of activation, achieving the maximum discharge capacities just at the first cycling without any activation needed. As for the as-spun alloys, its discharge potential characteristics could be improved obviously by adopting the technology of melt spinning. In addition, the melt spinning raised electrochemical cycle stability of the alloys, the main reason was that the melt spinning enhanced the anti-pulverization ability of the alloys. With spinning rate increasing, the discharge capacity of the alloys presented a tendency to increase firstly then decrease. Moreover, the electrochemical kinetics of the alloys showed the same trend under fixed condition.
基金financially supported by the National Natural Science Foundation of China(Nos.51371094 and 51471054)
文摘Nanocrystalline/amorphous LaMg(12)-type alloyNi composites with a nominal composition of LaMg(11)Ni+x wt% Ni(x=100,200) were synthesized by mechanical milling.Effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of alloys were systematically investigated.The hydrogen desorption properties were studied by Sievert apparatus and a differential scanning calorimeter(DSC).Thermodynamic parameters(△H and ΔS) for the hydrogen absorption and desorption of alloys were calculated by Van't Hoff equation.Hydrogen desorption activation energy of alloy hydride was estimated by Arrhenius and Kissinger methods.The increase in Ni content has a slight effect on the thermodynamic properties of alloys,but it significantly enhances the hydrogen absorption and desorption kinetics performance of alloys.Moreover,variation of milling time clearly affects the hydrogen storage properties of alloys.Hydrogen absorption capacity(C(100)~a) and hydrogen absorption saturation ratio(R(10)~a)(a ratio of the hydrogen absorption capacity at 10 min to the saturated hydrogen absorption capacity) have maximum values with milling time varying.But hydrogen desorption ratio(R(20)~d)(a ratio of the hydrogen desorption capacity at 20 min to the saturated hydrogen absorption capacity) always increases with milling time prolonging.Particularly,prolonging milling time from 5 to 60 h makes R(20)~d increase from 10.89% to 16.36% for the x=100 alloy and from 13.93% to 21.68% for the x=200 alloy,respectively.
基金supported by the National Natural Science Foundation of China(Nos.51161015 and 50961009)the National High Technology Research and Development Program of China(No.2011AA03A408)the Natural Science Foundation of Inner Mongolia(Nos.2011ZD10 and 2010ZD05)
文摘The La-Mg-Ni-based A2B7-type Lao.8_xNdx Mgo.2Ni3.35Alo.lSio.o5 （x = 0, 0.1, 0.2, 0.3, and 0.4） electrode alloys were prepared by casting and annealing. The influence of the partial substitution of Nd for La on the structure and electrochemical performances of the alloys was investigated. The structural analysis of X-ray diffraction and scanning electron microscopy reveals that the experimental alloys consist of two major phases： （La,Mg）2Ni7 with the hexagonal Ce2Ni7-type structure and LaNi5 with the hexagonal CaCus-type structure as well as some residual phases of LaNi3 and NdNis. The electrochemical measurements indicate that an evident change of the electrochemical performance of the alloys is associated with the substitution of Nd for La. The discharge capacity of the alloy first increases then decreases with the growing Nd content, whereas their cycle stability clearly grows all the time. Furthermore, the measurements of the high rate discharge ability, the limiting current density, and hydrogen diffusion coefficient all demonstrate that the electrochemical kinetic properties of the alloy electrodes first augment then decline with the rising amount of Nd substitution.
基金Projects(51371094,51471054)supported by the National Natural Science Foundation of China
文摘La was partially substituted by Ce with the aim of improving the electrochemical hydrogen storage performances ofLa1–xCexMgNi3.5Mn0.5 (x=0, 0.1, 0.2, 0.3, 0.4) alloys, and melt spinning technology was adopted to fabricate the alloys. Theidentification of XRD and SEM reveals that the experimental alloys consist of a major phase LaMgNi4 and a secondary phase LaNi5.The growth of spinning rate results in that the lattice constants and cell volume increase and the grains are markedly refined. Theelectrochemical measurement shows that the as-cast and spun alloys can obtain the maximum discharge capacities just at the firstcycle without any activation needed. With the increase of spinning rate, the discharge capacities of the alloys first increase and thendecline, whereas their cycle stabilities always grow. Moreover, the electrochemical kinetic performances of the alloys first increaseand then decrease with spinning rate growing.
文摘The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.
文摘Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase structure and microstructure of the samples were investigated using X-ray diffraction and scanning electron microscope, respectively. The complex permeability was measured using the impedance analyzer in the range of 1-100 MHz. The results indicate that with increasing Nd^3＋ content, the relative density and lattice parameter a of the sintered samples increase, whereas the real part of permeability （μ′） and the magnetic loss tangent （tan δ） decrease. The substitution of Nd^3＋ for Fe^3＋ forms a secondary phase on the grain boundary of the matrix, which strongly restrains the grain growth of the matrix.
基金the National Natural Science Foundation of China(51901105,51871125,51761032)Natural Science Foundation of Inner Mongolia,China(2019BS05005)。
文摘Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM) and pressure-composition isotherms(PCI) measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases(Ce,Sm)5 Mg41 and the minor phases(Ce,Sm)Mg12.After hydrogen absorption,these phases transform into the MgH2 and(Ce,Sm)H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the(Ce,Sm)H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of(Ce,Sm)H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.
基金Projects(51161015,51371094,51471054) supported by the National Natural Science Foundation of China
文摘Nanocrystalline and amorphous LaMg11Ni+x%Ni(x=100,200,mass fraction)alloys were synthesized by mechanicalmilling.The electrochemical hydrogen storage properties of the as-milled alloys were tested by an automatic galvanostatic system.The gaseous hydrogen absorption and desorption properties were investigated by Sievert’s apparatus and differential scanningcalorimeter(DSC)connected with a H2detector.The results indicated that increasing Ni content significantly improves the gaseousand electrochemical hydrogen storage performances of the as-milled alloys.The gaseous hydrogen absorption capacities andabsorption rates of the as-milled alloys have the maximum values with the variation of the milling time.But the hydrogen desorptionkinetics of the alloys always increases with the extending of milling time.In addition,the electrochemical discharge capacity andhigh rate discharge(HRD)ability of the as-milled alloys both increase first and then decrease with milling time prolonging.
基金financially supported by the National Natural Science Foundation of China (Nos. 50961009 and 51161015)the National High Technology Research and Development Program of China (No. 2011AA03A408)the National High Technology Research and Development Program of China (Nos. 2011ZD10 and 2010ZD05)
文摘In order to improve the electrochemical cycle stability of the RE–Mg–Ni-based A2B7-type electrode alloys, a small amount of Si has been added into the alloys.The casting and annealing technologies were adopted to fabricate the La0.8Mg0.2Ni3.3Co0.2Six(x = 0–0.2) electrode alloys. The impacts of the addition of Si and annealing treatment on the structures and electrochemical performances of the alloys were investigated systematically. The results obtained by XRD and SEM show that all the as-cast and annealed alloys are of a multiphase structure, involving two main phases(La, Mg)2Ni7and La Ni5 as well as a residual phase La Ni3. Both adding Si and the annealing treatment lead to an evident change in the phase abundance and cell parameters of(La, Mg)2Ni7and La Ni5 major phases of the alloy without altering its main phase component. Moreover, the annealing treatment has the composition of the alloy distributed more homogeneously overall and simultaneously causes the grain of the alloy to be coarsened obviously. The electrochemical measurements indicate that adding Si and the annealing treatment give a significant rise to the influence on the electrochemical performances of the alloys. In brief, the cycle stability of the as-cast and annealed alloys evidently increases with the rising of Si content, while their discharge capacities obviously decrease under the same circumstances. Furthermore, the electrochemical kineticproperties of the electrode alloys, including the high rate discharge ability, the limiting current density(IL), hydrogen diffusion coefficient(D), and the charge-transfer resistance, first augment and then decline with the rising of Si content. Similarly, it is found that the above-mentioned electrochemical properties first mount up and then go down with the rising annealing temperature.
基金supported by the National Natural Science Foundation of China(Nos.51161015 and 50961009)the National High-Technology Research and Development Program of China(No.2011AA03A408)the Natural Science Foundation of Inner Mongolia,China(Nos.2011ZD10 and 2010ZD05)
文摘In order to ameliorate the electrochemical hydrogen storage performances of La-Mg–Ni system A_2B_7-type electrode alloys, the partial substitution of M (M = Zr, Pr) for La was performed. The melt spinning technology was used to fabricate the La_(0.75-x)M_xMg_0.25Ni_3.2Co_0.2Al_0.1 (M = Zr, Pr; x = 0, 0.1) electrode alloys. The influences of the melt spinning and substituting La with M (M = Zr, Pr) on the structures and the electrochemical hydrogen storage characteristics of the alloys were investigated. The analysis of XRD, SEM, and TEM reveals that the as-cast and spun alloys have a multiphase structure composed of two main phases (La, Mg)_2Ni_7 and LaNi_5 as well as a residual phase LaNi_2 . The as-spun (M = Pr) alloy displays an entire nanocrystalline structure, while an amorphous-like structure is detected in the as-spun (M = Zr) alloy, implying that the substitution of Zr for La facilitates the amorphous formation. The electrochemical measurements exhibit that the substitution of Pr for La clearly increases the discharge capacity of the alloys; however, the Zr substitution brings on an adverse impact. Meanwhile, the M (M = Zr, Pr) substitution significantly enhances its cycle stability. The melt spinning exerts an evident effect on the electrochemical performances of the alloys, whose discharge capacity and high rate discharge ability (HRD) first mount up and then fall with the growing spinning rate, whereas their cycle stabilities monotonously augment as the spinning rate increases.
