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1.
《International Journal of Hydrogen Energy》2019,44(57):30218-30225
In the present study, NaXH3 (X = Mn, Fe, Co) perovskite type hydrides have been investigated by performing first-principles calculation. The results of the structural optimizations show that all these compounds have negative formation energy implying the thermodynamic stability and synthesisability. The mechanical stability of these compounds has been studied with the elastic constants. Moreover, the polycrystalline properties like bulk modulus, Poisson's ratio, etc. have been obtained using calculated elastic constants of interest compounds. The electronic properties have been studied and band structures have been drawn with the corresponding partial density of states. These plots indicated that NaXH3 hydrides show metallic characteristics. The charge transfer characteristics in these compounds have been studied with the Bader partial charge analysis. The phonon dispersion curves and corresponding density of states indicated that NaXH3 compounds are dynamically stable compounds. The investigation on hydrogen storage characteristics of NaXH3 compounds resulted in hydrogen storage capacities of 3.74, 3.70 and 3.57 wt% for X = Mn, Fe and Co, respectively. The present study is the first investigation of NaXH3 perovskite type hydrides as known up to date and may provide remarkable contribution to the future researches in hydrogen storage applications. 相似文献
2.
《International Journal of Hydrogen Energy》2019,44(23):11930-11938
The first principle calculations are used to investigate hydrogen storage properties of MgTiO3Hx and CaTiO3Hx (x = 0, 3, 6, and 8) perovskite compounds in cubic phase (Pm3 m). In order to examine the stability of these compounds, formation enthalpies are calculated and all compounds (except MgTiO3H6 and MgTiO3H8) are found to be stable. The second order elastic constants and related polycrystalline elastic moduli (e.g., shear modulus, Young's modulus, Poisson's ratio, Debye temperature, sound velocities) are determined and the results are discussed in detail. The mechanical stability determination indicates that MgTiO3, CaTiO3, and CaTiO3H6 compounds are only stable compounds and also MgTiO3 and CaTiO3H6 are ductile while CaTiO3 is a brittle material. Also, the mechanical anisotropy is discussed via two-dimensional (2D) and three-dimensional (3D) surfaces for mechanical stable compounds and they are found to have anisotropic behaviour (except linear compressibility for MgTiO3, CaTiO3). Electronic band structure and corresponding partial density of states (PDOS) and charge density have been plotted. Bader charge analysis have been done. MgTiO3 has metallic behaviour whereas CaTiO3 and CaTiO3H6 have semiconductor behaviour. Among all compounds, CaTiO3H6 is found to be only one that could be used in the hydrogen storage applications. For this compound, the gravimetric hydrogen storage capacity is calculated as 4.27 wt% and the hydrogen desorption temperature is obtained as 827.1 K. 相似文献
3.
《International Journal of Hydrogen Energy》2023,48(66):25821-25829
Based on the density functional theory, we investigate the electronic properties of the clusters M2B7 (M = Be, Mg, Ca) and their hydrogen storage properties systematically in this paper. Extensive global search results show that the global minimal structures of the three systems (Be2B7, Mg2B7 and Ca2B7) are heptagonal biconical structure, and the two alkaline earth metals are located at the top of the biconical. Chemical bonding analyses show that M2B7 clusters have 6σ and 6π delocalized electrons, which are doubly aromatic. At the wB97XD level, the three systems have good hydrogen storage capabilities. The hydrogen storage density of Be2B7 is as high as 23.03 wt%, while Mg2B7 and Ca2B7 also far exceed the hydrogen storage target set by the U.S. Department of Energy in 2017. Their average adsorption energies of H2 molecules all ranged from 0.1 eV/H2 to 0.48 eV/H2, which is fall in between physisorption and chemisorption. Extensive Born Oppenheimer molecular dynamics (BOMD) simulations show that the H2 molecules of the three systems can be completely released at a certain temperature. Therefore, M2B7 systems can achieve reversible adsorption of H2 molecules at normal temperature and pressure. It can be seen that the B7 clusters modified by alkaline earth metals may become a promising new nano-hydrogen storage material. 相似文献
4.
《International Journal of Hydrogen Energy》2019,44(29):15173-15182
XNiH3 (X = Li, Na, and K) perovskite type hydrides have been studied by using Density Functional Theory (DFT) and these materials are found to be stable and synthesizable. The X-ray diffraction patterns have been obtained and they indicate that all materials have the polycrystalline structure. The electronic properties have been investigated and it has been found that these structures show metallic character. The Bader partial charge analysis has also been performed. In addition, the elastic constants have been calculated and these materials are found to be mechanically stable. Using these elastic constants, the mechanical properties such as bulk modulus, shear modulus, Poisson's ratio have been obtained. Moreover, the Debye temperatures and thermal conductivities have been studied. The anisotropic elastic properties have been visualized in three dimensions (3D) for Young's modulus, linear compressibility, shear modulus and Poisson's ratio as well as with the calculation of the anisotropic factors. Additionally, the dynamical stability has been investigated and obtained phonon dispersion curves show that these materials are dynamically stable. Also, the thermal properties including free energy, enthalpy, entropy and heat capacity have been studied. The hydrogen storage properties have been examined and the gravimetric hydrogen storage capacities have been calculated as 4.40 wt%, 3.57 wt% and 3.30 wt% for LiNiH3, NaNiH3 and KNiH3, respectively. Furthermore, the hydrogen desorption temperatures have been obtained as 446.3 K, 419.5 K and 367.5 K for LiNiH3, NaNiH3 and KNiH3, respectively. 相似文献
5.
M.B. Baysal G. Surucu E. Deligoz H. Ozısık 《International Journal of Hydrogen Energy》2018,43(52):23397-23408
Density functional theory calculations are used herein to explore the effect of hydrogen on the electronic, mechanical and phonon properties of LaMgNi4 and its hydrides. The polycrystalline elastic moduli, Poisson's ratios and Debye temperatures are calculated based on the single-crystal elastic constants and Voigt-Reuss-Hill approximations. It is also found that all these materials are metallic behavior, ductile and anisotropic in nature. The mechanical anisotropy is discussed via several anisotropy indices and three-dimensional (3D) surface constructions. The effect of high temperature on the free energy, entropy, and heat capacity are also studied by using the quasi-harmonic Debye model. LaMgNi4 and its hydrides are found to be energetically, mechanically and dynamically stable. Also, they are thermodynamically stable and the order of phase stability is LaMgNi4H7 > LaMgNi4H4 > LaMgNi4H > LaMgNi4. In addition, the highest gravimetric hydrogen storage capacity is found to be 1.74 wt% for LaMgNi4H7. 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(17):10507-10515
In this study, Density Functional Theory (DFT) calculations have been performed for BaYO3 perovskite with the generalized gradient approximation (GGA) as implemented in Vienna Ab-initio Simulation Package (VASP). The structural optimization of BaYO3 perovskite have been studied for the five possible phases: cubic, tetragonal, hexagonal, orthorhombic and rhombohedral to determine the most stable phase of BaYO3 perovskite. It has been found that the cubic phase is the most stable one and electronic and mechanical properties of this phase have been investigated. Moreover, the elastic anisotropy has been visualized in detail by plotting the directional dependence of compressibility, Poisson ratio, Young's and Shear moduli for cubic phase. Then, hydrogen bonding to BaYO3 perovskite has been conducted and hydrogen storage properties of BaYO3Hx (x = 3 and 9) such as: formation energy, cohesive energy and gravimetric hydrogen storage capacity have been analyzed. Having no study about BaYO3 perovskite and hydrogen bonding in the literature makes this study the first considerations of BaYO3 perovskite. Hence, this work could enlighten the possible future studies. 相似文献
7.
《International Journal of Hydrogen Energy》2020,45(38):18782-18788
Hydrogen storage is a critical step for commercialisation of hydrogen consumed energy production. Among other storage methods, solid state storage of hydrogen attracts much attention and requires extensive research. This study rationally and systematically designs novel solid state hydrides; Li2CaH4 (GHD is obtained as −6.95 wt %) and Li2SrH4 (GHD is obtained as −3.83 wt %) using computational method. As a first step, we suggest and predict crystal structures of solid state Li2CaH4 and Li2SrH4 hydrides and look for synthesizability. Then, the mechanical stabilities of hydrides are identified using elastic constants. Both hydrides fulfil the well-known Born stability criteria, indicating that both Li2CaH4 and Li2SrH4 are mechanically stable materials. Several critical parameters, bulk modulus, shear modulus, Cauchy pressures, anisotropy factors of hydrides and bonding characteristics are obtained and evaluated. Furthermore, electronic and optical band structures of hydrides are computed. Both Li2CaH4 and Li2SrH4 have indirect bands gaps as 0.96 eV (Г-U) and 1.10 eV (Г-R). Thus, both materials are electronically semiconducting. Also, Bader charge analysis of hydrides have been carried out. Charge density distribution suggests an ionic-like (or polarized covalent) bonding interaction between the atoms. 相似文献
8.
The density functional theory is used to study the hydrogen storage abilities of alkali metal Li (Na, K), alkaline-earth metal Mg (Ca), and transition metal Ti (Ti, Sc, Y) decorated B28, which is the possible smallest all-boron cage and contains one hexagonal hole and two octagonal holes. The most stable structure of B28 explored by the calypso search is as same as that explored by Zhao et al. [Nanoscale 7(2015)15086]. It is calculated that the hollow sites outside of the cavities should be the most stable for all metals except for Ti. The average adsorption energy of H2 molecules (Ead) adsorbed by each Na (Ca, K, Mg, Sc, Y and Li) atom outside of the B28 cage are in the range from 0.2 to 0.6 eV, which is suitable for hydrogen storage under near-ambient conditions. However, the largest hydrogen gravimetric density (HGD) for the B28Sc3-12H2 structure is smaller than the target of 5.5 wt% by the year 2017 specified by the US Department of Energy (DOE). Therefore, the metal Ti (Sc) decorated all-boron cage B28 should not be good candidates for hydrogen storage. The calculated desorption temperature and the molecular dynamic simulation indicate that the B28M3-nH2 (M = Na, Li, Ca, K, Mg, Y) structures are easy to desorb the H2 molecules at the room temperature (T = 300 k). Furthermore, the B28 cages bridged by the sp2-terminated B5 chain can hold Na (Li, Ca, K, Mg, Y) atoms to capture hydrogen molecules with moderate Ead and HGD. These findings suggest a new route to design hydrogen storage materials under the near-ambient conditions. 相似文献
9.
《International Journal of Hydrogen Energy》2019,44(36):20121-20132
In this work, we predict a range of favorable functional properties of (LiBH4)2NH3BH3, a relatively new member of the boron-containing metal borohydride ammonia borane family, by means of ab initio calculations, as well as its parent compounds, LiBH4 and NH3BH3, for comparisons. Both the mechanical and dynamical stabilities of this new compound have been demonstrated theoretically for the first time. Results from elastic modulus calculations show that the mechanical properties of (LiBH4)2NH3BH3 are remarkably improved compared with its parent compounds. Secondly, Electronic structure results show that it remains to an insulator with large band gap typical of the boron-containing hydrogenous family, but the band gap can be tuned by the compositions of NH3BH3 and LiBH4. Charge analysis demonstrates that charge transfers in individual layers of LiBH4 and NH3BH3 are similar to LiBH4 and NH3BH3, respectively. A measurable amount of charge transfers from the LiBH4 layers to the NH3BH3 layers result in enhanced activation properties for hydrogenation and dehydrogenation in (LiBH4)2NH3BH3. Thirdly, Free energies of six possible dehydrogenation reactions have been calculated from 0 K to 700 K, and the results show that combination of NH3BH3 and LiBH4 can reduce the dehydrogenation energies compared with the parent compounds, a result consistent with recent experiments. Meanwhile, the N–B bond strengths increase and thereby borazine and diborane formation are reduced upon dehydrogenation. 相似文献
10.
Lingwei Lu Shuang Ni Gang Liu Xiaoxiang Xu 《International Journal of Hydrogen Energy》2017,42(37):23539-23547
The crystal structure of a photocatalyst generally plays a pivotal role in its electronic structure and catalytic properties. In this work, we synthesized a series of La/Cr co-doped perovskite compounds ATiO3 (M = Ca, Sr and Ba) via a hydrothermal method. Their optical properties and photocatalytic activities were systematically explored from the viewpoint of their dependence on structural variations, i.e. impact of bond length and bond angles. Our results show that although La/Cr co-doping helps to improve the visible light absorption and photocatalytic activity of these wide band gap semiconductors, their light absorbance and catalytic performance are strongly governed by the TiO bond length and TiOTi bond angle. A long TiO bond and deviation of TiOTi bond angle away from 180° deteriorate the visible light absorption and photocatalytic activity. The best photocatalytic activity belongs to Sr0.9La0.1Ti0.9Cr0.1O3 with an average hydrogen production rate ~2.88 μmol/h under visible light illumination (λ ≥ 400 nm), corresponding to apparent quantum efficiency ~ 0.07%. This study highlights an effective way in tailoring the light absorption and photocatalytic properties of perovskite compounds by modifying cations in the A site. 相似文献
11.
Bilal Rehmat M.A. Rafiq Y. Javed Z. Irshad Nisar Ahmed S.M. Mirza 《International Journal of Hydrogen Energy》2017,42(15):10038-10046
Density functional theory (DFT) was used to study mechanical properties of orthorhombic and cubic LiBeH3 and cubic NaBeH3. The band gaps were estimated using different approximations available in the WIEN2k code. The elastic constants of LiBeH3 and NaBeH3 were calculated. Both hydrides were found to be stable mechanically. From elastic constants, the bulk modulus and the linear bulk modulus along crystallographic axes of single crystal were calculated. The calculated values of linear bulk moduli were in good agreement with the reported theoretical values. Young's and Shear moduli, Poisson's ratio and micro-hardness for ideal polycrystalline LiBeH3 and NaBeH3 were also calculated. Both these hydrides can be classified as brittle materials according to obtained results. The values of bulk, shear and Young's moduli obtained in our study were higher than those reported for other popular hydrides for hydrogen storage. Shear and elastic anisotropic factors along with Debye temperature are also discussed using theoretical elastic constants. 相似文献
12.
Lusheng Wang Jun Ding Xia Huang Kun Song Bo Liu Xiangguo Zeng 《International Journal of Hydrogen Energy》2018,43(29):13328-13338
Element doping is an effective way to improve the performance of hydrogen storage. The influences of Ti- and Hf-substituted dopants on the hydrogen storage and mechanical properties in a Zirconium-Cobalt alloy have been investigated by the first principle method. The results show that the Ti and Hf atoms preferentially occupy the Zr atoms to form new Zr7Co8Ti and Zr7Co8Hf compounds. The cohesive energy of Zr7Co8Ti and Zr7Co8Hf are ?7.518 eV/atom and ?7.531 eV/atom, thus Zr7Co8Hf shows a better structural stability than Zr7Co8Ti. The B/G ratio of Zr7Co8Ti and Zr7Co8Hf are 3.42 and 3.89, respectively, which indicates that Ti doping could increase the ductility of the alloy, thus improving the recycling performance of the alloy. The calculation for the electronic structure, mechanical property and structural stability may provide an effective way and theoretical evidence for the better design and optimization of hydrogen storage materials. 相似文献
13.
《International Journal of Hydrogen Energy》2022,47(12):7884-7891
The magnesium-lanthanum-hydrogen systems possess the goodish stability and high hydrogen storage capacity, which make them perspective as commercial Mg-based hydrogen storage materials. The exploration of these intriguing properties evolving from small atomic and molecule cluster to bulk phase are, to our knowledge, the longstanding challenge. Here, we perform a theoretical study on the structural and electronic properties of Mg3LaHn (9 ≤ n ≤ 20) clusters by using the Crystal Structure AnaLYsis by Particle Swarm Optimization method combined with density functional theory calculations. It is found that Mg3LaH15 is the most stable cluster in the series, with hydrogen storage capacity of 6.6 wt% and adsorption energy of 2.76 eV. The present results offer new insights for the design and synthesis of novel hydrogen storage materials in the future. 相似文献
14.
《International Journal of Hydrogen Energy》2022,47(15):9357-9371
The role of Mn substitution in FeTi towards the hydrogenation kinetics and hydrogen storage capacity was investigated using a combination of experimental and theoretical tools. Pristine and Mn-substituted FeTi was produced by electro-deoxidation of oxide precursors, such as natural ilmenite, titania and manganese dioxide. The produced materials were evaluated for hydrogen storage capacity. Ab-initio density functional theory (DFT) calculations were performed to understand the thermodynamics and kinetics of hydrogen absorption in pristine and doped FeTi. DFT calculations demonstrate that although thermodynamic and kinetic parameters of hydrogen absorption with Mn substitution is similar to those in the pristine FeTi, oxygen affinity of Mn at the surface is higher than Fe or Ti. We conclude that Mn acts as a sacrificial oxidizing element and oxidizes more readily at the surface over Fe or Ti, resulting in easy activation of the FeTi alloy. We show superior cyclic-hydrogen absorption behavior in bulk in FeTi with Mn substitution. After 20 charge-discharge cycles, the measured hydrogen storage capacity of FeTi with Mn substitution was steady ~120 mA h/g (0.8 wt %), which is noticeably higher than that of pristine FeTi. The experimental and theoretical results shows that in case of a practical hydrogen storage scenario, Mn substitution will benefit in reducing absorption fatigue in FeTi. Further, most likely it may not be possible to use pristine FeTi phase. 相似文献
15.
Majid EL Kassaoui Marwan Lakhal Abdelilah Benyoussef Abdallah El Kenz Mohammed Loulidi 《International Journal of Hydrogen Energy》2021,46(52):26426-26436
Two strategies of decoration by three elements Z = Li, Be and Na in cyclic site, and substitution of Zn by Mg and Cd in unit cell were used in the framework of functional density theory to tune the hydrogen storage properties of metal-organic framework-5 (MOF-5) based on Zn whose decomposition temperature and initial gravimetric capacity are 300 K and 1.57 wt% respectively.Based on the adsorption of hydrogen molecules in the crystal surface at three different adsorption sites with three orientations of H2, we show that our system may reach a maximum gravimetric storage capacity of 4.09 wt% for multiple hydrogen molecules. Moreover, the functionalization of Z combined to the substitution, shows an exceptional improvement of hydrogen storage properties. For example, Mg-MOF-5 decorated with Li2 has a capacity up to 5.41 wt% and 513 K as desorption temperature. 相似文献
16.
《International Journal of Hydrogen Energy》2023,48(50):19153-19159
Doping can modify the properties of metal hydrogen storage materials significantly. Currently, the metal doping is a frequent strategy, while the non-metal cation doping has not been examined extensively so far. In this study, the effects of NH4+ doping on the hydrogen storage properties of different metal hydrides, including TiH2, Ti0·25V0·25Nb0·25Zr0·25H2, Ti0·5V0·5H2 and VH2, are investigated by first-principles calculations. It is found that the NH4+ presents a good affinity for metal hydrides and the NH4+ incorporation leads to charge redistribution and formation of dihydrogen bond. Furthermore, the NH4+ doping in metal hydrides is favorable for enhancing the hydrogen storage capacity and decreasing the thermal stability simultaneously. The possible reason for the NH4+ doping induced destabilization in metal hydrides is the relatively weak interaction between NH4+ and hydrogen atoms. 相似文献
17.
《International Journal of Hydrogen Energy》2021,46(65):32936-32948
Two-dimensional (2D) materials can be regarded as potential hydrogen storage candidates because of their splendid chemical stability and high specific surface area. Recently, a new dumbbell-like carbon nitride (C4N) monolayer with orbital hybridization of sp3 is reported. Motivated from the above exploration, the hydrogen adsorption properties of Li-decorated C4N monolayer are comprehensively investigated via first principles calculations based on the density functional theory (DFT). It is found that the Dirac points and Dirac cones exists in the Brillouin zone (BZ) from the calculated electronic structure and indicates the C4N can be used as an excellent topological material. Also, the calculated phonon spectra demonstrate that the C4N monolayer owns a strong stability. Moreover, the calculated binding energy of decorated Li atom is bigger than its cohesive energy and results in Li atoms disperse over the surface of C4N monolayer uniformly without clustering. In addition, the Li8C4N complex can capture up to 24H2 molecules with an optimal hydrogen adsorption energy of −0.281 eV/H2 and achieves the hydrogen storage density of 8.0 wt%. The ab initio molecular dynamics (AIMD) simulations suggest that the H2 molecules can be desorbed quickly at 300 K. This study reveals that Li-decorated C4N monolayer can be served as a promising hydrogen storage material. 相似文献
18.
Mg(BH4)2·2NH3 is a relatively new compound considered for hydrogen storage. The fundamental properties of the compound were comprehensively studied using first-principles calculations, such as crystal structure and electronic structure, reaction Gibbs free energy and possible reaction pathway. The calculated crystal structure is in good agreement with the experimental and other theoretical results. Results from electronic density of states (DOS) and electron localization function (ELF) show the covalent characteristics of the N–H and the B–H bonds, and the weak ionic interactions between the Mg atom and the NH3 ligands or the (BH4)− ligands. The reaction Gibbs free energies of several possible decomposition reactions were calculated between 0 and 700 K. All the reactions are exothermic. The most likely reaction pathway of the dehydrogenation reaction was clarified to show five distinct steps. 相似文献
19.
Luis F. Contreras Vasquez Yinzhe Liu David Book 《International Journal of Hydrogen Energy》2021,46(13):9151-9162
The synthesis, thermodynamic destabilisation and hydrogen sorption properties of the M0.2Ca0.8MgH4 hydride system, where (M = Na or Li) have been investigated. Samples were mechanically milled under argon for 5, 10 and 15 h; then characterised by X-ray diffraction (in/ex-situ), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) coupled with a mass spectrometer (MS). On Li and Na substitution into Ca–Mg–H ternary hydride, diffraction peaks shifted to higher angles. 2 and 3 endothermic reactions were observed for the Li0.2Ca0.8MgH4 and Na0.2Ca0.8MgH4. The maximum amount of hydrogen release was achieved for the 5 h milled Na0.2Ca0.8MgH4 hydride from 298 °C to 386 °C accounting for 3.5 wt % of H2. 相似文献
20.
Somwan Chumphongphan Mark Paskevicius Drew A. SheppardCraig E. Buckley 《International Journal of Hydrogen Energy》2013
A simple mechanical milling and annealing process has been used to synthesize CaNi5-based hydrogen storage alloys. Heat treatment at 800 °C under vacuum results in the formation of a crystalline CaNi5 phase. Secondary phases, including Ca2Ni7 and Mo–Ni, are formed when substituting Mo for Ni. Replacement of Ni by Al or Mo leads to an increase in the unit cell volume of the CaNi5 phase. The hydrogen storage capacity of all substituted alloys is reduced and the plateau pressures are lower than those of pure CaNi5. Fairly flat plateau regions are retained for all compositions except the CaNi4.8Mo0.2 composition where a Ca2Ni7 phase is dominant. The incorporation of Mo also causes slow sorption kinetics for the CaNi4.9Mo0.1 alloy. CaNi4.9Al0.1 maintains its initial hydrogen absorption capacity for 20 cycles performed at 85 °C but the other substituted alloys lose their capacity rapidly, especially the CaNi4.8Mo0.2 composition. 相似文献