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1.
In this study, the structural properties and hydrogen adsorption energy of the fluorinated metal-organic framework (MOF)-801 were evaluated using density functional theory (DFT). We calculated the Zr–F bond distance to be approximately 0.225 nm, which is longer than the bond distance in zirconium fluoride compounds. Due to the electronegativity of F, this site was considered as an adsorption site for hydrogen. We determined the adsorption energy to be ?5 kcal/mol per hydrogen (H2) molecule, which is higher than that of H2 in pristine MOF. This value is also slightly lower than the adsorption energy in a metal-decorated MOF. The introduction of F atoms is determined to enhance the binding capacity of MOF-801.  相似文献   

2.
Graphdiyne (GDY) is a new member of carbon allotropes consisting of sp and sp2 hybridized carbon atoms. In this work, the hydrogen adsorption on Calcium (Ca) decorated GDY and the influence of adatom on structural properties of GDY are investigated, using first principles plane wave calculations with Van der Waals corrections. The results show that similar to graphyne (GY) and unlike carbon nanotube (CNT), fullerene and graphene, clustering of Ca on GDY hinders due to the higher binding energy of the adatom to the carbon frame than the Ca cohesive energy. It can be seen that the Ca-decoration promotes hydrogen storage capacity of GDY, extremely (Eads = ?0.266 and ?0.066 eV for Ca-decorated and pristine GDY, respectively). It is concluded that, the best site for the Ca trapping is 18-membered ring in which, Ca lies in-plane of GDY (Eads = ?3.171 eV). Fourteen H2 molecules (with the average adsorption energy of ~0.2 eV/H2) can be adsorbed on the Ca atom from one side. The hydrogen storage capacity is estimated to be as high as 17.95 wt% for the both sides of GDY. So, the Ca-decorated GDY is offered as a promising candidate for hydrogen storage applications.  相似文献   

3.
A metal-organic framework based on Ni (II) as metal ion and trimasic acid (TMA) as organic linker was synthesized and introduced into MgH2 to prepare a Mg-(TMA-Ni MOF)-H composite through ball-milling. The microstructures, phase changes and hydrogen storage behaviors of the composite were systematically studied. It can be found that Ni ion in TMA-Ni MOF is attracted by Mg to form nano-sized Mg2Ni/Mg2NiH4 after de/rehydrogenation. The hydriding and dehydriding enthalpies of the Mg-MOF-H composite are evaluated to be −74.3 and 78.7 kJ mol−1 H2, respectively, which means that the thermodynamics of Mg remains unchanged. The absorption kinetics of the Mg-MOF-H composite is improved by showing an activation energy of 51.2 kJ mol−1 H2. The onset desorption temperature of the composite is 167.8 K lower than that of the pure MgH2 at the heating rate of 10 K/min. Such a significant enhancement on the sorption kinetic properties of the composite is attributed to the catalytic effects of the nanoscale Mg2Ni/Mg2NiH4 derived from TMA-Ni MOF by providing gateways for hydrogen diffusion during re/dehydrogenation processes.  相似文献   

4.
Herein, a novel flower-like Ni MOF with good thermostability is introduced into MgH2 for the first time, and which demonstrates excellent catalytic activity on improving hydrogen storage performance of MgH2. The peak dehydrogenation temperature of MgH2-5 wt.% Ni MOF is 78 °C lower than that of pure MgH2. Besides, MgH2-5 wt.% Ni MOF shows faster de/hydrogenation kinetics, releasing 6.4 wt% hydrogen at 300 °C within 600 s and restoring about 5.7 wt% hydrogen at 150 °C after dehydrogenation. The apparent activation energy for de/hydrogenation reactions are calculated to be 107.8 and 42.8 kJ/mol H2 respectively, which are much lower than that of MgH2 doped with other MOFs. In addition, the catalytic mechanism of flower-like Ni MOF is investigated in depth, through XRD, XPS and TEM methods. The high catalytic activity of flower-like Ni MOF can be attributed to the combining effect of in-situ generated Mg2Ni/Mg2NiH4, MgO nanoparticles, amorphous C and remaining layered Ni MOF. This research extends the knowledge of elaborating efficient catalysts via MOFs in hydrogen storage materials.  相似文献   

5.
Bio-hydrogen (H2) production from renewable biomass has been accepted as a promising method to produce an alternative fuel for the future. In this study, fermentative hydrogen production from cornstalk (CS) hydrolysate pretreated by alkaline-enzymolysis method was investigated. Meanwhile, a five-factor and five-level orthogonal experimental array was designed to study the influences of Ca(OH)2 concentration, alkaline hydrolysis time, alkaline hydrolysis temperature, cellulase and xylanase dosages on cornstalk pretreatment and hydrogen production. A maximum reducing sugar yield of 0.59 g/g-CS was obtained at Ca(OH)2 0.5%, hydrolysis temperature 115 °C, hydrolysis time 1.5 h, cellulase dosage 4000 U/g-CS and xylanase 4000 U/g-CS. Under this same condition, the maximum hydrogen yields of 168.9 mL/g-CS, 357.6 mL/g-CS, and 424.3 mL/g-CS were obtained at dark-fermentation, photo-fermentation, and two-stage fermentation respectively. It's also found that the significance of these five parameters on H2 production followed from high to low order as: Ca(OH)2 concentration, cellulase dosage, xylanase dosage, hydrolysis time, and hydrolysis temperature. By comparing the energy produced with the energy spent, the maximum Energy Sustainability Index (ESI) value of 1.11 was obtained at the two-stage fermentation. The results suggested that two-stage fermentation is a promising and efficient way for hydrogen production from lignocellulosic biomass.  相似文献   

6.
Using first principles study, we have investigated the hydrogen storage capacity of Ca-coated B40. Our result shows that Ca prefers to adsorb on the top hollow center of heptagonal ring of B40 due to the large binding energy of ?2.820 eV. Bader charges calculation indicates that charges transfer from Ca to B40 result in an induced electric field so that H2 molecules are polarized and adsorbed onto the surface of B40 without dissociation. The Ca6B40 complex can adsorb up to 30 H2 molecules with average adsorption energy of ?0.177 eV/H2 and the hydrogen storage gravimetric density reaches up to 8.11 wt.%, higher than the goal from DOE by the year 2020. These findings will suggest a new and potential structure for hydrogen storage in the future.  相似文献   

7.
Using density functional theory, we designed novel cluster structure units with large surface areas for hydrogen storage through the surface functionalization of a stable Si12C12H24 nanocage with CONH2 organic molecules and Li atoms. Two structures, namely, Si12C12H12(CONHLi)12 and Si12C12H12(CONLi2)12, are proposed. The structures are stable at room temperature and show suitable hydrogen adsorption energies. Modification can enlarge the surface area of the two structures compared with the original cluster. In addition, the O and N anions participate in the adsorption of H2 molecules in addition to the Li cations. The average hydrogen binding energy for Si12C12H12(CONHLi)12·82H2 is 0.135 eV/H2 and the average hydrogen binding energy for Si12C12H12(CONLi2)12·84H2 is 0.134 eV/H2 when these cluster structure units reach their maximum H2 uptake capacity. The gravimetric hydrogen percentages are 13.18 and 12.60 wt%, respectively. With such a structural unit, a suitable linker allows the assembly of metal organic framework-like porous materials that display satisfactory hydrogen storage properties at room temperature.  相似文献   

8.
Hydrogen provides reliable, sustainable, environmental and climatic friendly energy to meet world's energy requirement and it also has high energy density. Hydrogen is relevant to all of the energy sectors-transportation, buildings, utilities and industry. In all of these sectors, hydrogen-rich gas streams are needed. Thus, hydrogen-selective membrane technology with superior performances is highly demanded for separation and purification of hydrogen gas mixtures. In this study, novel [Al4(OH)2(OCH3)4(H2N-BDC)3xH2O (CAU-1) MOF membranes with accessible pore size of 0.38 nm are evaluated for this goal of hydrogen purification. High-quality CAU-1 membranes have been successfully synthesized on α-Al2O3 hollow ceramic fibers (HCFs) by secondary growth assisted with the homogenously deposited CAU-1 nanocrystals with a size of 500 nm as seeds. The energy-dispersive X-ray spectroscopy study shows that the HCFs substrates play dual roles in the membrane preparation, namely aluminum source and as a support. The crystals in the membrane are intergrown together to form a continuous and crack-free layer with a thickness of 4 μm. The gas sorption ability of CAU-1 MOF materials is examined by gas adsorption measurement. The isosteric heats of adsorption with average values of 4.52 kJ/mol, 12.90 kJ/mol, 12.82 kJ/mol and 27.99 kJ/mol are observed for H2, N2, CH4, and CO2 respectively, indicating different interactions between CAU-1 framework and these gases. As-prepared HCF supported CAU-1 membranes are tested by single and binary gas permeation of H2/CO2, H2/N2 and H2/CH4 at different temperatures, feed pressures and testing time. The permeation results show preferential permeance of H2 over CO2, N2, and CH4 with high separation factors of 12.34, 10.33, and 10.42 for H2/CO2, H2/N2, H2/CH4, respectively. The temperature, pressure and test time dependent studies reveal that HCFs supported CAU-1 membranes possess high stability, resistance to cracking, temperature cycling, high reproducibility, these of which combined with high separation efficiency make this type of MOF membranes are promising for hydrogen recycling from industrial exhausts.  相似文献   

9.
Copper(II)phthalocyanine-incorporated metal organic framework (CuPc/MOF) composite material was synthesized for application as an electrocatalyst for hydrogen evolution reaction (HER). The composite exhibited excellent electroactivity compared to the unmodified MOF, as confirmed by the diffusion coefficients (D) values of 3.89 × 10−7 and 1.57 × 10−6 cm2 s−1 for MOF and CuPc/MOF, respectively. The D values were determined from cyclic voltammetry (CV) experiments performed in 0.1 mol L−1 tetrabutylammonium perchlorate/dimethyl sulfoxide (TBAP/DMSO) electrolyte. The Tafel slope determined from the CV data of CuPc/MOF-catalysed HER for 0.450 mol L−1 H2SO4, was 176.2 mV dec−1, which was higher than that of the unmodified MOF (158.3 mV dec−1). The charge transfer coefficients of MOF and CuPc/MOF were close to 0.5, signifying the occurrence of a Volmer reaction involving either the Heyrovsky or the Tafel mechanism for hydrogen generation. For both MOF and CuPc/MOF, the exchange current density (i0) improved with increase in the concentration of the hydrogen source (i.e. 0.033–0.45 mol L−1 H2SO4) Nonetheless, the CuPc/MOF composite had a higher i0 value compared with the unmodified MOF. Thus CuPc/MOF has promise as an efficient electrocatalyst for HER.  相似文献   

10.
Single layer blue phosphorus (SLBP) is a promising two–dimensional material for nanoelectronic devices, but the electronic structure and hydrogen storage property of modified SLBP received little attention. Li atoms can be strongly bonded on SLBP in a 1:1 Li/P ratio with a binding energy larger than the cohesive energy of bulk Li. The geometric structure of SLBP suggests the 3s3p orbitals of the P atom hybridize in sp3 manner. But our analyses show that the 3s and 3p orbitals form bonding and antibonding orbitals respectively. The 3s orbitals are fully occupied as they have much lower energies, and the bonding orbitals formed by P 3p are occupied in pure SLBP. The decorated Li atoms transfer their 2s electrons to the antibonding orbital formed by P 3p. The Li atoms exist as +1 cations and they are ionically bonded on SLBP. H2 molecules adsorbed on the Li+ cations are strongly polarized and form strong adsorption. When two H2 are adsorbed on each Li atom decorated at the 1:1 Li/P ratio, the hydrogen storage capacity reaches 9.52 wt% but the H2 molecules are arranged in two layers with the adsorption energy ?0.168 eV/H2. When the Li atoms are decorated alternatively on the two sides of the P6 rings with a Li/P ratio of 1:2, each Li atom can absorb two H2 molecules in a single–layer; the hydrogen storage capacity is 5.48 wt% and the adsorption energy reaches ?0.227 eV/H2. These results mean the Li–decorated SLBP can work at ambient temperature with high reversible hydrogen storage capacity.  相似文献   

11.
Hydrogen storage properties of co-functionalized 2D GaS monolayer have been systematically investigated by first-principles calculations. The strength of the binding energy of hydrogen (H2) molecules to the pristine GaS surface shows the physisorption interactions. Co-functionalized GaS sheet by Li, Na, K and Ca atoms enhanced the capacity of binding energies of hydrogen and strength of hydrogen storage considerably. Besides, DFT calculations show that there is no structural deformation during H2 desorption from co-functionalized GaS surface. The binding energies of per H2 molecules is found to be 0.077 eV for pristine GaS surface and 0.064 eV–0.37 eV with the co-functionalization of GaS surface. Additionally, in the presence of applied external electric field enhanced the strength of binding energies and it is found to be 0.09 eV/H2 for pristine GaS case and 0.19 eV/H2 to 0.38 eV/H2 for co-functionalized GaS surface. Among the studied GaS monolayer is found to be the superior candidate for hydrogen storage purposes. The theoretical studies suggest that the electronic properties of the 2D GaS monolayer show the electrostatic behavior of hydrogen molecules which confirms by the interactions between adatoms and hydrogen molecules before and after hydrogen adsorption.  相似文献   

12.
Hydrogen and methane are considered as the promising fuels in the future, however, one of the obstacles to their utilizations is the lack of efficient storage and safe transportation materials. In this theoretical work, a novel kind of metal–organic framework (MOF) is designed using heterofullerene as linker from density functional theory calculations and first-principles molecular dynamics simulations. Based on grand canonical Monte Carlo simulations, we explore the adsorption performances of H2 and CH4 in the proposed porous MOF materials, which exhibit spectacular capacities for hydrogen storage as well as for methane storage after Li doping, both achieving the targets set by U.S. Department of Energy at workable conditions.  相似文献   

13.
The hydrogen storage capacity of M-decorated (M = Li and B) 2D beryllium hydride is investigated using first-principles calculations based on density functional theory. The Li and B atoms were calculated to be successfully and chemically decorated on the Surface of the α-BeH2 monolayer with a large binding energy of 2.41 and 4.45eV/atom. The absolute value was higher than the cohesive energy of Li and B bulk (1.68, 5.81eV/atom). Hence, the Li and B atoms are strongly bound on the beryllium hydride monolayer without clustering. Our findings show that the hydrogen molecule interacted weakly with B/α-BeH2(B-decorated beryllium hydride monolayer) with a low adsorption energy of only 0.0226 eV/H2 but was strongly adsorbed on the introduced active site of the Li atom in the decorated BeH2 with an improved adsorption energy of 0.472 eV/H2. Based on density functional theory, the gravimetric density of 28H2/8li/α-BeH2) could reach 14.5 wt.% higher than DOE's target of 6.5 wt. % (the criteria of the United States Department of Energy). Therefore, our research indicates that the Li-decorated beryllium hydride monolayer could be a candidate for further investigation as an alternative material for hydrogen storage.  相似文献   

14.
In this paper, we describe a case-study exploring the use of 600 MW of power from New Zealand's Manapouri Power Station to produce hydrogen for export via water electrolysis. Three H2 carriers were considered: liquid H2, ammonia, and toluene hydrogenation/methylcyclohexane dehydrogenation. Processes were simulated in Aspen's HYSYS for each of the carriers to determine their associated energy and annualised capital expenditure costs. We found that the total capital investment for all carriers was surprisingly consistent, but with quite different splits between the electrolysis and carrier formation plants. Based on our analysis the energy availability for liquid H2 ranged from 53.9 to 60.7% depending on the energy cost associated with cryogenic H2 liquefaction. The energy availability for liquid ammonia was 37.5% after conversion back to H2, or 53.6% if the ammonia can be used directly as a fuel. For toluene/methylcyclohexane the energy availability was 41.2%. The total of the electricity and annualised capital costs per kg of H2 ranged from NZ$5.63 to NZ$6.43 for liquid H2, NZ$6.24 to NZ$8.91 for ammonia and was NZ$7.86 for toluene/methylcyclohexane, using a net electricity cost of NZ$70/MWh. The cost of hydrogen (or energy in the case of direct use ammonia) was more strongly influenced by the efficiency of energy retention than on capital investment, as the electricity costs contributed approximately two thirds of total costs. In the long-term, liquid hydrogen looks to be the most versatile H2 carrier, but significant infrastructure investment is required.  相似文献   

15.
The Lithium–Boron Reactive Hydride Composite System (Li-RHC) (2 LiH + MgB2/2 LiBH4 + MgH2) is a high-temperature hydrogen storage material suitable for energy storage applications. Herein, a comprehensive gas-solid kinetic model for hydrogenation is developed. Based on thermodynamic measurements under absorption conditions, the system's enthalpy ΔH and entropy ΔS are determined to amount to −34 ± 2 kJ∙mol H2−1 and −70 ± 3 J∙K−1∙mol H2−1, respectively. Based on the thermodynamic behavior assessment, the kinetic measurements' conditions are set in the range between 325 °C and 412 °C, as well as between 15 bar and 50 bar. The kinetic analysis shows that the hydrogenation rate-limiting-step is related to a one-dimensional interface-controlled reaction with a driving-force-corrected apparent activation energy of 146 ± 3 kJ∙mol H2−1. Applying the kinetic model, the dependence of the reaction rate constant as a function of pressure and temperature is calculated, allowing the design of optimized hydrogen/energy storage vessels via finite element method (FEM) simulations.  相似文献   

16.
The hydrogen storage (H-storage) capacity of various boranes and alanes have been investigated using density functional theory (DFT) based M05-2X method employing 6–31+G** basis set. The changes in the H-storage capacities of borane and alane upon substitution of antipodal atoms in the cages by C, Si, and N have also been investigated. It is found from the calculations that a maximum of 20 H2 molecules can be adsorbed on the deltahedron faces of these cages. The maximum gravimetric density has been observed for boranes when compared to alanes. The H-storage capacity of closo-borane dianion [B12H12]2−, monocarborane [CB11H12]1−, dicarborane [C2B10H12], and closo-azaborane [NB11H12] cages is almost similar (∼22 wt.%). Among these cages, BBB dianion show higher binding energy (BE) and BE per H2 molecule (BE/nH2) which are 181.06 and 9.03 kJ/mol, respectively. In the case of alanes, dicarbalane [C2Al10H12] has maximum H-storage capacity of 11.6 wt.%. Based on these findings, a new MOF with carborane (MOF-5CC) as linker has been designed. The calculation on the new MOF-5BCC reveals that it has H-storage capacity of 6.4 wt.% with BE/nH2 of 3.02 kJ/mol.  相似文献   

17.
With the shortage of global fossil energy and the increasing crisis of environmental deterioration, hydrogen energy has become an environmentally benign alternative as a clean energy source. In most studies on photocatalytic hydrogen production, novel photocatalytic material has played an important role to enhance the hydrogen production rate. In this study, the optimal conditions for the synthesis of MoS2 were established through series of characterizations with 190 °C calcination temperature and 1 wt% PEG surfactant addition. The best conditions for synthesizing MOF include copper nitrate as the copper precursor, 30% ultrasonic amplitude, and 240 °C calcination temperature. After adding 1 wt% MOF in MOS2, a flower-like structure with small particle size, uniform distribution, regularity, and large surface pores, has been formed, where its unit is modified with many rough, porous, and high specific surface area octahedral structures. In addition, 1MOF/MOS2 has the most negative conduction band edge (?0.135 V), the smallest charge transfer resistance (Rct = 1.78 Ω), the largest photo current (11.1 mA/cm2), the lowest PL spectral peak intensity, and excellent photocatalytic stability. The above morphological features and optical properties can significantly form more active sites, enhance the electron transfer rate, and inhibit the electron-hole recombination, thus making the MOF/MOS2 composite photocatalyst achieve the maximum hydrogen production capacity (626.3 μmol g?1 h?1).  相似文献   

18.
Catalytic steam gasification of char derived from low-rank coal possesses substantial potential as a source of hydrogen energy and syngas feedstocks, and its performances are largely associated with the employed catalysts. Therein, ion-exchangeable Na or Ca species are always regarded as excellent in-situ catalysts in low-rank coal. In this paper, gasification of Na-Char, Ca-Char and a Na/Ca-Char mixture with different partial pressures of steam was performed within a temperature range of 700–900 °C using a micro fluidized bed reaction analyzer. The results indicate that Na and Ca species could accelerate the gas release rate during gasification and even significantly increase H2 production, in sharp contrast to non-catalytic gasification. Variations in the product gases during Na-Char and Ca-Char gasification were completely different, which associated with the different deactivation pathways and catalytic reaction mechanisms of Na and Ca catalysts. With an increasing gasification temperature, the decreasing trend of H2 production for Na-Char gasification was mainly due to the loss of Na during gasification. Conversely, the enhancement of Ca activity promoted the H2 production. The H2/CO ratio of Ca-Char gasification at 700 °C approximately ranged from 1.0 to 2.0 as a function of the partial pressure of steam, which suggested catalytic gasification can be suitable for hydrogen-rich production and subsequent synthesis reactions. In addition, gasification of Na/Ca-Char mixture produced a higher hydrogen content in the product gases than that of Na-Char or Ca-Char gasification alone, particularly for the 30%Na/70%Ca-Char mixture. It implies that the high H2 production of 70%Ca30%Na-Char mixture was attributed to the cooperative effects of the Na and Ca species on the catalytic activity. This study provides comprehensive information regarding the effects of ion-exchangeable Na, Ca and a Na/Ca mixture on the hydrogen production and syngas composition during steam gasification, which provides new insight into the utilization of low-rank coal.  相似文献   

19.
Based on the DFT calculations within GGA approximation, we have systematically studied the ScBn (n = 1–12) clusters and their hydrogen storage properties. The results show that the maximal adsorption for H2 molecules is ScB7 6H2 structure with the hydrogen storage mass fraction about 9.11%. For ScBn·mH2 clusters as n = 7 or 9–12, the average binding energies between 0.202 and 0.924 eV are suggestively conducive to hydrogen storage. In these medium clusters, the moderate adsorption strength can benefit application of hydrogen energy owning to easily adsorption and dissociation on H2 molecules at room temperature and 1 bar pressure. Furthermore, the absorption spectrum is also investigated from TDDFT calculation. An obvious red-shift of spectral lines at 4.2 eV or 5.6 eV is detected with the increase of number of H2 molecules. It can be regard as ‘fingerprint’ spectrum in experiment to indicate adsorption capacity of H2 molecules for ScBn·mH2 nanostructures.  相似文献   

20.
The hydrogen storage (1–10H2) properties of single- and double-side lithium decorated ThMoB4-type graphene (Li/ThMoB4C) are systematically investigated by density functional first-principles calculations within Dmol3 package. After well-converged geometry optimizations, it is found that the binding energy of Li adatom is higher enough, and there is no adatom clustering. The average adsorption energies of 1–6 H2 deviate in 0.20–0.27 eV/H2 range, which is providing a convenient physical adsorption-desorption cycle. A detailed examination of the binding mechanism between the constituents of the H2 adsorbed Li-decorated systems is presented by density of states, Mulliken charge analysis, electron density and density difference calculations. For further decoration and adsorption with 12Li adatom and 72H2 molecules, the computation yields a high gravimetric density of 14.5 wt % with the acceptable adsorption energy. In this way, it is concluded that Li/ThMoB4 system can be considered as a promising hydrogen storage medium.  相似文献   

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