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1.
《International Journal of Hydrogen Energy》2022,47(16):9829-9834
A recent commentary by Santhosh and Ravindran on our paper (Int. J. Hydrogen Energy 2014, 39:10,606) demonstrated that the interaction between H2 and MXene (Sc2C and Ti2C) phases are not Kubas-type and should be of weak physisorption, and thus made a conclusion that 2D Sc2C and Ti2C are not suitable for practical hydrogen storage applications. In this responses, we recalculated hydrogen adsorption on 2D Sc2C and Ti2C by using different exchange-correlation functionals. And based on the calculated results, bare MXenes (especially the Ti2C) are suitable as hydrogen storage materials at temperatures of several tens degrees lower than room temperature. And the hydrogen adsorptions on the MXenes terminated with oxygen group were also investigated. Among the Ti2C, Sc2C and their oxygen-functional counterparts, the binding energy of H2 on Sc2CO2 surface is the closest to the ideal range of 0.16–0.42 eV/H2 at ambient conditions, and thus the Sc2C with oxygen group is expected to be more suitable as hydrogen storage materials. 相似文献
2.
《International Journal of Hydrogen Energy》2020,45(7):4693-4702
The dihydrogen storage capacity of ScxNy (x + y = 4) compounds have been theoretically investigated at different levels. At B3LYP-D3/6-311G(3df,3pd) level, ScN3 has multiple isomers with similar energies, which is an interference of hydrogen storage research. Sc2N2 and Sc3N has four and three isomers, respectively. For both systems, the lowest-lying isomers are planar Sc2N2 01 and Sc3N 01, which are energetically much low-lying by at least 20 kcal/mol than the other isomers, respectively. Sc3N 01 can adsorb 8H2 with gravimetric uptake capacity of 9.77 wt %. It satisfies the target specified by US DOE, however, some hydrogen molecules will dissociate and bond atomically on scandium atoms. The strong binding energy (0.66 eV/H2) exceeds the reversible adsorption range (0.1–0.4 eV/H2), which will cause high operating temperature to desorb hydrogen during the application process. Sc2N2 01 can adsorb 9H2 in the molecular form. The H2 gravimetric uptake capacity of Sc2N2 01 (9H2) (13.33 wt %) exceeds the target set by US Department of Energy, moreover, its average adsorption energy (0.32 eV/H2) is in the reversible adsorption range. The interaction of Sc2N2 01 with H2 molecules is considered by means of the bond critical points (bcp) in the quantum theory of atoms in molecules (QTAIM). The Gibbs free energy corrected adsorption energy points that the adsorption of Sc2N2 01(9H2) is energetically favorable below 240 K. Therefore, in ScxNy (x + y = 4), the planar compound Sc2N2 01 is more suitable to be a dihydrogen adsorption material. 相似文献
3.
Ashish Bhatnagar Sunita K. Pandey Viney Dixit Vivek Shukla Rohit R. Shahi M.A. Shaz O.N. Srivastava 《International Journal of Hydrogen Energy》2014
The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH2–NaAlH4 composite. De/rehydrogenation study reveals that MgH2–NaAlH4 composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH4 and MgH2. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH2–NaAlH4 composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH2–NaAlH4 catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH2–NaAlH4 is diminished to 0.45 wt.%. 相似文献
4.
The intermetallic compound Mg0.65Sc0.35 was found to form a nano-structured metal hydride composite system after a (de)hydrogenation cycle at temperatures up to 350 °C. Upon dehydrogenation phase separation occurred forming Mg-rich and Sc-rich hydride phases that were clearly observed by SEM and TEM with the Sc-rich hydride phase distributed within Mg/MgH2-rich phase as nano-clusters ranging in size from 40 to 100 nm. The intermetallic compound Mg0.65Sc0.35 showed good hydrogen uptake, ca. 6.4 wt.%, in the first charging cycle at 150 °C and in the following (de)hydrogenation cycles, a reversible hydrogen capacity (up to 4.3 wt.%) was achieved. Compared to the as-received MgH2, the composite had faster cycling kinetics with a significant reduction in activation energy Ea from 159 ± 1 kJ mol−1 to 82 ± 1 kJ mol−1 (as determined from a Kissinger plot). Two-dehydrogenation events were observed by DSC and pressure–composition-isotherm (PCI) measurements, with the main dehydrogenation event being attributed to the Mg-rich hydride phase. Furthermore, after the initial two cycles the hydrogen storage capacity remained unchanged over the next 55 (de)hydrogenation cycles. 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(90):38282-38294
While Mg/MgH2 system has a high hydrogen storage capacity, its sluggish hydrogen desorption rate has hindered practical applications. Herein, we report that the hydrogen absorption and desorption kinetics of Mg/MgH2 system can be significantly improved by using the synergetic effect between Nb2CTx MXene and ZrO2. The catalyst of Nb2CTx MXene loading with ZrO2 (ZrO2@Nb2CTx) is successfully synthesized, and the dehydrogenation activation energy of MgH2 becomes as low as 60.0 kJ/mol H2 when ZrO2@Nb2CTx is used as the catalyst, which is far smaller than the case of ZrO2 (94.8 kJ/mol H2) and Nb2CTx MXene (125.6 kJ/mol H2). With the addition of ZrO2@Nb2CTx catalyst, MgH2 can release about 6.24 wt.% and 5.69 wt.% of hydrogen within 150 s at 300 °C and within 900 s even at 240 °C, respectively. Moreover, it realizes hydrogen absorption at room temperature, which can uptake 2.98 wt.% of hydrogen within 1800 s. The catalytic mechanism analysis demonstrates that the in-situ formed nanocomposites can weaken the Mg–H bonding and provide more hydrogen diffusion channels, enabling the dissociation and recombination of hydrogen under milder reaction conditions. 相似文献
6.
R. Lavanya V.J. Surya I. Lakshmi K. Iyakutti V. Vasu H. Mizuseki Y. Kawazoe 《International Journal of Hydrogen Energy》2014
Hydrogen storage in titanium dioxide (TiO2) functionalized (10, 10) armchair single walled carbon nanotube (SWCNT) is investigated through first principle calculations using density functional theory (DFT). This first principles study uses Vienna Ab-initio Simulation Package (VASP) with ultrasoft pseudopotentials and local density approximation (LDA). The necessary benchmark and other systematic calculations were carried out to project the hydrogen storage capability of the designed system. Interestingly, the TiO2 molecules functionalized on the outer surface of SWCNT do not undergo any dimerization/clustering thus giving excellent stability and usable gravimetric hydrogen storage capacity of 5.7 wt.% and the value nearly fulfills the US DOE target (i.e. 6 wt.%). The band structure and density of states (DOS) plots suggest that the functionalization can lead a way to transform the nature (metallic → semiconducting) of the pristine SWCNT. The nominal values of H2 storage capacity and binding energies give much hope for using CNT functionalized with TiO2 as a practical and reversible hydrogen storage medium (HSM). 相似文献
7.
Madiha Makhdoom Sikander Azam Tahani A. Alrebdi Saleem Ayaz Khan Azhar Iqbal Mohammed Benali Kanoun Souraya Goumri-Said 《International Journal of Hydrogen Energy》2021,46(2):2405-2412
Fuel cell technology based on stationary and mobile applications is needing new hydrogen storage materials equipped with huge gravimetric and volumetric hydrogen densities. Examining the fundamental properties of hydrides is an important part of such process, mainly to understand the structure change's impact on the hydrogen storage. Herein, we applied ab-initio density functional theory using full potential linear augmented plane method to explore the effect of rubidium and cesium doping in sodium borohydride, NaBH4. The electronic structure calculations exposed the semiconducting nature of NaBH4 and derived doped structures NaRbBH4 and NaCsBH4. The hydrogen (H2) storage capacity is found 10.66 wt %, 3.27 wt % and 2.36 wt % within a reasonable free energy of ?28.514 kJ/mol, ?29.709 kJ, ?28.51 kJ/mol for NaBH4, NaRbBH4 and NaCsBH4 respectively from quasi-harmonic approximation. Also, we extracted the heat capacity and Debye temperature from vibrational analysis based on phonon calculation. The discovered features show the potential use of presented sodium borohydrides for practical H2 storage devices. 相似文献
8.
Kinetic properties of La2Mg17–x wt.% Ni (x = 0–200) hydrogen storage alloys prepared by ball milling
Xia Li Tai Yang Yanghuan Zhang Dongliang Zhao Huiping Ren 《International Journal of Hydrogen Energy》2014
The as-cast La2Mg17 with different amount of Ni powders were mixed through ball milling to produce a new type of La2Mg17–x wt.% Ni (x = 50, 100, 150, 200) alloy. The microstructures of the alloys were characterized by XRD technique, the results show that the crystal structure transfers to amorphous one with the increasing amount of Ni powders. La2Mg17–50 wt.% Ni alloy reaches the highest hydrogen absorption capacity of 5.13 wt.% at 300 °C under 2 MPa hydrogen pressure due to its amorphous structure. Furthermore, La2Mg17–50 wt.% Ni alloy expresses fast hydriding kinetics and absorbs 4.99 wt.% hydrogen gas in 200 s. The hydrogen desorption ability described as discharge capacity during electrochemical reaction is fade next to La2Mg17–200 wt.% Ni alloy, attributed to the less Mg2NiH4 with lower enthalpies and easier to release H2. The maximum discharge capacity of La2Mg17–200 wt.% Ni alloy reaches to exciting 980.90 mAh/g, while the La2Mg17 alloy is only 18.10 mAh/g with inconspicuous improvement of cycle stability. These dramatic difference in electrochemical performance reflect the consequence of sluggish dehydriding process of La2Mg17–50 and 100 wt.% Ni alloys again. Whereas La2Mg17–200 wt.% Ni alloy has lower resistance both on alloy surface and in the bulk. 相似文献
9.
The effect of charge on the dihydrogen storage capacity of Sc2–C6H6 has been investigated at B3LYP-D3/6-311G(d,p) level. The neutral system Sc2–C6H6 can store 8H2 with gravimetric density of 8.76 wt %, and one H2 dissociates and bonds atomically on the scandium atom. The adsorption of 8H2 on Sc2–C6H6 is energetically favorable below 155 K. The atom-centered density matrix propagation (ADMP) molecular dynamics simulations show that Sc2–C6H6 can adsorb 3H2 within 1000 fs at 300K. Compared with Sc2–C6H6, the charged systems can adsorb more hydrogen molecules with higher gravimetric density, and all the H2 are adsorbed in the molecular form. The gravimetric densities of Sc2–C6H6+ and Sc2–C6H62+ are 9.75 and 10.71 wt%. Moreover, the maximum adsorption of charged systems are favorable in wider temperature range. Most importantly, the ADMP-MD simulations indicate that Sc2–C6H62+ can adsorb 6 hydrogen molecules within 1000 fs at 300K. It can be found that the gravimetric density (6.72 wt%) of Sc2–C6H62+ still exceeds the target of US Department of Energy (DOE) under ambient conditions. 相似文献
10.
Xianyun Peng Baozhong Liu Xin Zhao Yanping Fan Qiuming Peng Shumin Han 《International Journal of Hydrogen Energy》2013
The influences of ultrahigh pressure (UHP, under 5 GPa) on phase compositions, phase morphologies and hydrogen storage properties of LaMg4Ni alloys were studied. The X-ray diffraction patterns show that the as-cast alloy consists of La2Mg17, LaMg2Ni and Mg2Ni phases, whereas a new LaMg3 phase is observed in the UHP samples in addition to LaMg2Ni and Mg2Ni phases. The scanning electron microscopy graphs indicate that the phase distribution is more homogenous in the UHP alloys than in the as-cast one. Additionally, the microstructure of the UHP alloy heat-treated at 973 K is finer than that at 823 K. Both the reversible hydrogen storage capacity and the plateau of hydrogen pressure of the UHP alloys are close to those of the as-cast one. Of particular interest is that both UHP alloys exhibit better activation properties compared with the as-cast alloy. Moreover, the dehydriding onset temperature of the UHP alloys (5 GPa at 973 K) is about 490 K, which is obviously lower than that of the as-cast alloy. The amount of hydrogen desorption in the UHP alloy (5 GPa at 973 K) is 2.69 wt.% at 573 K, which corresponds to 89.6% of the saturated capacity. However, the corresponding values change to 1.75 wt.% and 58.3% in the as-cast alloy, respectively. It is confirmed the UHP treatment is one of effective approaches to tune the hydrogen storage performances of those rare earth–magnesium–nickel alloys. 相似文献
11.
《International Journal of Hydrogen Energy》2020,45(11):6780-6792
We computationally investigate the hydrogen storage properties of carbyne C10-ring structure on either Dnh or D(n/2)h symmetry decorated with calcium (Ca) atoms adsorbed on its outer surface. The calculations are carried out on DFT-GGA-PW91 and DFT-GGA-PBE levels of theory as implemented in Biovia Materials Studio modeling and simulation software. To account for van der Waals interactions we also carried out calculations using DFT-D method of Grimme. Dmol3 is used to calculate total energies, HOMO-LUMO electronic charge density, Mulliken population analysis, and electrostatic potential fitting charges (ESP). Based on these results: i) the average binding energy of Ca atom doping to C10-ring is ~2.3 eV (PW91) and ~2.1 eV (PBE). ii) Up to seven H2 molecules per Ca atom can be physically adsorbed with an average energy of ~0.2 eV per H2 molecule. iii) This physisorption leads to 8.09 wt percentage (wt. %) for the gravimetric storage capacity. According to these results, calcium-decorated carbyne C10-ring structure is excellent candidate for hydrogen storage at ambient conditions with application to fuel cells. 相似文献
12.
《International Journal of Hydrogen Energy》2019,44(13):6437-6447
In this work, we report DFT calculations of the energy formation and stability of multi-vacancies in a unit of Zeolite Template Carbon (C39H9). We label as Vn the respective vacancy where n carbon atoms have been removed from the pristine C39H9 structure. The results show that V2, V4, V6 and V9 are the most stable vacancies on the ZTC structure. This result agrees with many other studies. Besides, the most stable vacancy of ZTC structure is when nine carbon atoms are removed (V9) from the ZTC structure. The formation of pentagon rings in the reconstruction of the ZTC vacancy give drastic effect on the energetics stability. Therefore, the formation of pentagon rings eliminates the dangling bonds thus lowering the energy formation. It is also carried out the decoration of ZTC vacancy with Lithium and Calcium atoms, this is the way to use de ZTC vacancy decorated as a medium for hydrogen storage. The results show that the ZTC vacancy decorated with 3 Lithium atoms can adsorb a maximum of nine hydrogen molecules (3 hydrogen molecules per Lithium atom). This gives a gravimetric storage capacity of 4.44 wt percent (wt. %), which is not enough for meeting DOE gravimetric target. On the other hand, to reach DOE gravimetric target, the study of ZTC vacancy decorated with 3 Calcium atoms is carried out, which can adsorb maximum of fifteen hydrogen molecules (5 hydrogen molecules per Calcium atom), this gives gravimetric storage capacity of 5.81 wt %, which meet DOE gravimetric targets, besides the binding energy of hydrogen molecules on ZTC vacancy decorated with 3 Calcium is calculated. These energies are in the range 0.2453–0.2053 eV/H2, which are desirable energies for hydrogen adsorption. This is demonstrated by building isotherm adsorption path. The results show that forming vacancies on ZTC structure decorated with three Calcium atoms (3CaC30H9) is good candidate as medium for hydrogen storage. 相似文献
13.
The effect of light metal ion decoration of the organic linker in metal-organic framework MOF-5 on its hydrogen adsorption with respect to its hydrogen binding energy (ΔB.E.) and gravimetric storage capacity is examined theoretically by employing models of the form MC6H6:nH2 where M = Li+, Na+, Be2+, Mg2+, and Al3+. A systematic investigation of the suitability of DFT functionals for studying such systems is also carried out. Our results show that the interaction energy (ΔE) of the metal ion M with the benzene ring, ΔB.E., and charge transfer (Qtrans) from the metal to benzene ring exhibit the same increasing order: Na+ < Li+ < Mg2+ < Be2+ < Al3+. Organic linker decoration with the above metal ions strengthened H2-MOF-5 interactions relative to its pure state. However, amongst these ions only Mg2+ ion resulted in ΔB.E. magnitudes that were optimal for allowing room temperature hydrogen storage applications of MOF-5. A much higher gravimetric storage capacity (6.15 wt.% H2) is also predicted for Mg2+-decorated MOF-5 as compared to both pure MOF-5 and Li+-decorated MOF-5. 相似文献
14.
《International Journal of Hydrogen Energy》2023,48(40):15143-15153
To study the dihydrogen storage capacity of Sc6O8 and Y6O8 complexes, the stability and hydrogen adsorption behavior have been investigated by using density functional theoretical calculations. The lowest-lying isomers are cage-like complexes Sc6O8 01 and Y6O8 01, which are energetically much low-lying by at least 40.43 kcal/mol than the other isomers, respectively. Sc6O8 01 can adsorb 26H2 with gravimetric uptake capacity of 11.64 wt%. The average adsorption energy (ΔEave) is 0.12 eV/H2, which is in the reversible adsorption range. The Y6O8 01 seem have little ability to adsorb hydrogen molecules, because the ΔEave Y6O8 01 (1H2) is just only 0.065 eV. However, the binding capacity increases with the number of adsorbed H2 increasing. Y6O8 01 can adsorb 32H2 with ΔEave of 0.11 eV/H2, and the gravimetric uptake capacity is 8.89 wt%. Various characterization methods indicate that both transition metals and nonmetals in Sc6O8 01 and Y6O8 01 can effectively adsorb hydrogen molecules, and these two compounds can be regarded as candidate materials of dihydrogen adsorption under suitable condition. 相似文献
15.
Senem KarahanMehmet Zahmak?ran Saim Özkar 《International Journal of Hydrogen Energy》2011,36(8):4958-4966
There has been rapidly growing interest for materials suitable to store hydrogen in solid state for transportation of hydrogen that requires materials with high volumetric and gravimetric storage capacity. B-N compounds such as ammonia-triborane, ammonia-borane and amine-borane adducts are well suited for this purpose due to their light weight, high gravimetric hydrogen storage capacity and inclination for bearing protic (N-H) and hydridic (B-H) hydrogens. In addition to them, more recent study [26] has showed that hydrazine borane with a gravimetric hydrogen storage capacity of 15.4% wt needs to be considered as another B-N compound that can be used for the storage of hydrogen. Herein we report for the first time, metal catalyzed hydrolysis of hydrazine borane (N2H4BH3, HB) under air at room temperature. Among the catalyst systems tested, rhodium(III) chloride was found to provide the highest catalytic activity in this reaction. In the presence of rhodium(III) chloride, the aqueous solution of hydrazine borane undergoes fast hydrolysis to release nearly 3.0 equivalent of H2 at room temperature with previously unprecedented H2 generation rate TOF = 12000 h−1. More importantly, it was found that in the catalytic hydrolysis of hydrazine borane the reaction between hydrazine borane and water proceeds almost in stoichiometric proportion indicating that the efficient hydrogen generation can be achieved even from the highly concentrated solution of hydrazine borane or in the solid state when water added to the solid hydrazine borane. This finding is crucial especially for on-board application of the existing system. The work reported here also includes (i) finding the solubility of hydrazine borane plus its stability against self-hydrolysis in water, (ii) the definition of reaction stoichiometry and the identification of reaction products for the catalytic hydrolysis of hydrazine borane, (iii) the collection of wealthy kinetic data to demonstrate the effect of substrate and catalyst concentrations on the hydrogen generation rate and to determine the rate law for the catalytic hydrolysis of hydrazine borane, (iv) the investigation of the effect of temperature on the rate of hydrogen generation and determination of activation parameters (Ea, ΔH#, and ΔS#) for the catalytic hydrolysis of hydrazine borane. 相似文献
16.
Serge Nyallang Nyamsi Mykhaylo V. Lototskyy Volodymyr A. Yartys Giovanni Capurso Moegamat Wafeeq Davids Sivakumar Pasupathi 《International Journal of Hydrogen Energy》2021,46(36):19046-19059
MgH2-based hydrogen storage materials are promising candidates for solid-state hydrogen storage allowing efficient thermal management in energy systems integrating metal hydride hydrogen store with a solid oxide fuel cell (SOFC) providing dissipated heat at temperatures between 400 and 600 °C. Recently, we have shown that graphite-modified composite of TiH2 and MgH2 prepared by high-energy reactive ball milling in hydrogen (HRBM), demonstrates a high reversible gravimetric H storage capacity exceeding 5 wt % H, fast hydrogenation/dehydrogenation kinetics and excellent cycle stability. In present study, 0.9 MgH2 + 0.1 TiH2 +5 wt %C nanocomposite with a maximum hydrogen storage capacity of 6.3 wt% H was prepared by HRBM preceded by a short homogenizing pre-milling in inert gas. 300 g of the composite was loaded into a storage tank accommodating an air-heated stainless steel metal hydride (MH) container equipped with transversal internal (copper) and external (aluminium) fins. Tests of the tank were carried out in a temperature range from 150 °C (H2 absorption) to 370 °C (H2 desorption) and showed its ability to deliver up to 185 NL H2 corresponding to a reversible H storage capacity of the MH material of appr. 5 wt% H. No significant deterioration of the reversible H storage capacity was observed during 20 heating/cooling H2 discharge/charge cycles. It was found that H2 desorption performance can be tailored by selecting appropriate thermal management conditions and an optimal operational regime has been proposed. 相似文献
17.
Brahamananda Chakraborty Pranoy Ray Nandini Garg Srikumar Banerjee 《International Journal of Hydrogen Energy》2021,46(5):4154-4167
Using the state-of-the art Density Functional Theory simulations, here we report the hydrogen storage capability in titanium decorated ?- Graphene, an advanced 2D allotrope of carbon which is made of hexagonal, pentagonal and heptagonal ring of carbon and metallic in nature. Titanium is strongly bonded on the surface of ?- Graphene and each Ti can bind maximum of 9H2 having average adsorption energy of ?0.30 eV and average desorption temperature of 387 K yielding gravimetric H2 uptake of 13.14 wt%, much higher than the prescribed limit of 6.5 wt % by DoE's. The interaction of Ti on ?- Graphene have been presented by electronic density of states analysis, charge transfer and plot for spatial distribution of charge. There is orbital interaction between Ti 3d and C 2p of ?- Graphene involving transfer of charge whereas bonding of hydrogen molecules is through Kubas type of interactions involving charge donation from σ orbitals of hydrogen molecules to the vacant 3d orbital of Ti and the subsequent back donation to σ1 orbital of hydrogen from filled 3d orbital of Ti. The structural stability of the system at temperatures corresponding to the highest temperature at which H2 desorbs was verified using ab-initio Molecular Dynamics calculations and presence of sufficient energy barrier for diffusion which prevents clustering between metal atoms assures the practical viability of the system as high capacity H2 adsorbing material. Overall, found that Ti doped Ψ-Graphene is stable, 100% recyclable and has high hydrogen storage capacity with suitable desorption temperature. As a result of our findings, we are confident that Ti doped Ψ-Graphene may be used as a potential hydrogen adsorbing material in the upcoming clean, green, hydrogen economy. 相似文献
18.
Jai Singh M.S.L. HudsonS.K. Pandey R.S. TiwariO.N. Srivastava 《International Journal of Hydrogen Energy》2012
In this work, Mg doped zinc oxide (MgxZn1−xO, x = 5, 10 and 20 at. %) nanowires were successfully prepared by two step process. Initially, ZnO nanowires were grown by thermal evaporation of Zn powder under oxygen atmosphere. Mg powder was doped in as grown ZnO through solid state diffusion at low temperature. Energy dispersive x-ray spectroscopy (EDAX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–Visible absorption spectra analysis reveals that the Mg doping on ZnO nanowires induces lattice strain in ZnO. Rietveld analysis of XRD data confirms the wurtzite structure and a continuous compaction of the lattice (in particular, the c-axis parameter) as x increases. The hydrogenation properties of ZnO nanowires and Mg doped ZnO (MgxZn1−xO, x = 0, 5, 10 and 20 at. %) nanowires were studied. The hydrogenated samples were further investigated through XRD and Fourier transform infrared spectroscopy (FTIR). The hydrogen storage capacity of as grown ZnO nanowires has been estimated to be 0.57 wt. % H2 at room temperature. However, the hydrogen storage capacity gets increased to ∼1 wt. % upon doping ZnO with 10 at. % Mg. Further increase in Mg concentration decreases the hydrogen storage capacity of ZnO nanowires. Thus for 20 at. % Mg doped ZnO; the hydrogen absorption capacity gets decreased from ∼1 wt. % to 0.74 wt. %. The mechanism of hydrogen storage in ZnO nanowires and Mg doped samples of ZnO has been discussed. 相似文献
19.
Sandip Haldar Sankha Mukherjee Farheen Ahmed Chandra Veer Singh 《International Journal of Hydrogen Energy》2017,42(36):23018-23027
In this study, we studied defect-engineering and lithium decoration of 2D phosphorene for effective hydrogen storage using density functional theory. Contrary to graphene, it is found that the presence of point-defects is not preferable for anchoring of H2 molecules over defective phosphorene. According to previous research, strategies such as defect engineering, metal decoration, and doping enhance the hydrogen storage capacity of several 2D materials. Our DFT simulations show that point defects in phosphorene do not improve the hydrogen storage capacity compared to pristine phosphorene. However, selective lithium decoration over the defective site significantly improves the hydrogen adsorption capacity yielding a binding energy of as high as ?0.48 eV/H2 in Li-decorated single vacancy phosphorene. Differential charge densities and projected density of states have been computed to understand the interactions and charge transfer among the constituent atoms. Strong polarization of the H2 molecule is evidenced by the charge accumulation and depletion. The PDOS shows that the presence of Li leads to enhanced charge transfer. The maximum gravimetric density was investigated by sequentially adding H2 molecules to the Li-decorated single vacancy defective phosphorene. The Li-decorated single vacancy phosphorene is found to possess a gravimetric density of around 5.3% for hydrogen storage. 相似文献
20.
Terry D. Humphries Keelie T. Munroe Tamara M. DeWinter Craig M. Jensen G. Sean McGrady 《International Journal of Hydrogen Energy》2013
Aluminum hydride (alane; AlH3) has been identified as a leading hydrogen storage material by the US Department of Energy. With a high gravimetric hydrogen capacity of 10.1 wt.%, and a hydrogen density of 1.48 g/cm3, AlH3 decomposes cleanly to its elements above 60 °C with no side reactions. This study explores in detail the thermodynamic and spectroscopic properties of AlH3; in particular the α, α′ and γ polymorphs, of which α′-AlH3 is reported for the first time, free from traces of other polymorphs or side products. Thermal analysis of α-, α′-, and γ-AlH3 has been conducted, using DSC and TGA methods, and the results obtained compared with each other and with literature data. All three polymorphs were investigated by 1H MAS-NMR spectroscopy for the first time, and their 27Al MAS-NMR spectra were also measured and compared with literature values. AlH3·nEt2O has also been studied by 1H and 27Al MAS-NMR spectroscopy and DSC and TGA methods, and an accurate decomposition pathway has been established for this adduct. 相似文献