首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Inspired by the TM−N4 coordination environment in single-atom catalysts, four novel TM-decorated B24N24 (TM = Sc, Ti) fullerenes with six TM−N4 or TM−B4 units are designed. Molecular dynamic simulations confirm that the four TM6B24N24 fullerenes are thermodynamically stable. Their hydrogen storage properties were investigated using density functional theory calculations. Sc/Ti atoms bind to the N4/B4 cavities with an average interaction energy of 6.30–11.96 eV. Hence, the problem of clustering can be avoided. 36H2 could be adsorbed with average hydrogen adsorption energies of 0.18–0.55 eV. The lowest hydrogen desorption temperatures at atmospheric pressure for Sc6B24N24(N4)–36H2, Sc6B24N24(B4)–36H2, Ti6B24N24(N4)–36H2, and Ti6B24N24(B4)–36H2 are 255 K, 318 K, 243 K, and 408 K, respectively. The maximum hydrogen gravimetric densities of the Sc6B24N24 and Ti6B24N24 systems are 7.74 wt% and 7.50 wt%, respectively. Therefore, the novel Sc6B24N24 and Ti6B24N24 could be suitable as potential hydrogen storage materials at ambient temperature.  相似文献   

2.
A three dimensional (3D) dumbbell-like nanostructure composed by interconnected fullerenes and nanotubes with Lithium decoration and boron-doping (37Li@C139B31) has been proposed in virtue of density functional theory (DFT) and first-principles molecular dynamics (MD) simulations which shows excellent geometric and thermal stability. First-principles calculations are performed to investigate the hydrogen adsorption onto the 37Li@C139B31. The results indicate that B substitution can improve the metal binding and the average binding energy of 37 adsorbed Li atoms on the C139B31 (2.79 eV) is higher than the cohesive energy of bulk Li (1.63 eV) suppressing the clustering. Meanwhile, the H2 storage gravimetric density of 178H2@37Li@C139B31 reaches up to 15.9 wt% higher than the year 2020 target from the US department of energy (DOE). The average adsorption energy of H2 molecules falls in a desirable range of 0.18–0.27 eV. Moreover, grand canonical ensemble Monte Carlo (GCMC) simulations reveal that at room temperature the hydrogen gravimetric density (HGD) adsorbed on 37Li@C139B31 reaches up to 11.6 wt% at 100 bars higher than the DOE 2020 target. Our multiscale simulations indicate that our proposed nanostructure provides a promising medium for hydrogen storage.  相似文献   

3.
The hydrogen adsorption capacity of dual-Ti-doped (7, 7) single-walled carbon nanotube (Ti-SWCNTs) has been studied by the first principles calculations. Ti atoms show different characters at different locations due to local doping environment and patterns. The dual-Ti-doped SWCNTs can stably adsorb up to six H2 molecules through Kubas interaction at the Ti2 active center. The intrinsic curvature and the different doping pattern of Ti-SWCNTs induce charge discrepancy between these two Ti atoms, and result in different hydrogen adsorption capacity. Particularly, eight H2 molecules can be adsorbed on both sides of the dual-Ti decorated SWCNT with ideal adsorption energy of 0.198 eV/H2, and the physisorption H2 on the inside Ti atom has desirable adsorption energy of 0.107 eV/H2, ideal for efficient reversible storage of hydrogen. The synergistic effect of Ti atoms with different doping patterns enhances the hydrogen adsorption capacity 4.5H2s/Ti of the Ti-doped SWCNT (VIII), and this awaits experimental trial.  相似文献   

4.
This study uses first-principles calculations to investigate and compare the hydrogen storage properties of Ti doped benzene (C6H6Ti) and Ti doped borazine (B3N3H6Ti) complexes. C6H6Ti and B3N3H6Ti complex each can adsorb four H2 molecules, but the former has a 0.11 wt% higher H2 uptake capacity than the latter. Ti atoms bind to C6H6 more strongly than B3N3H6. The hydrogen adsorption energies with Gibbs free energy correction for C6H6Ti and B3N3H6Ti complexes are 0.17 and 0.45 eV, respectively, indicating reversible hydrogen adsorption. The hydrogen adsorption properties of C6H6Ti have also been studied after boron (B) and nitrogen (N) atom substitutions. Several B and N substituted structures between C6H6Ti and B3N3H6Ti with different boron and nitrogen concentration and at different positions were considered. Initially, one boron and one nitrogen atom is substituted for two carbon atoms of benzene at three different positions and three different structures are obtained. Seven structures are possible when four carbon atoms of benzene are replaced by two boron and two nitrogen atoms at different positions. The hydrogen storage capacity of the C6H6Ti complex increases as boron and nitrogen atom concentrations increases. The positions of substituted boron and nitrogen atoms have less impact on H2 uptake capacity for the same B and N concentration. The position and concentration of B and N affects the H2 adsorption energy as well as the temperature and pressure range for thermodynamically favorable H2 adsorption. The H2 desorption temperature for all the complexes is found to be higher than 250 K indicates the stronger binding of H2 molecules with these complexes.  相似文献   

5.
The B6Be2 and B8Be2 clusters, adopting fascinating inverse sandwich-like geometries, were recently predicted with quantum chemical calculations. Both systems exhibit the high stability and double aromaticity with 4σ/6π or 6σ/6π delocalized electrons. The hydrogen storage of two systems is studied in the present paper. Our calculations show that B6Be2 and B8Be2 clusters have the ultra-high capacity hydrogen storage, each Be site can bound up with seven H2 molecules, corresponding to a gravimetric density of 25.3 wt percentage (wt%) for B6Be2 and 21.1 wt% for B8Be2, respectively, which far exceeds the target (5.5 wt%) proposed by the US department of energy (DOE) in 2017. The average absorption energies of 0.10–0.45 eV/H2 for B6Be2 and 0.11–0.50 eV/H2 for B8Be2 at the wB97XD level suggest that both systems are ideal for reversible hydrogen storage and release. The reversibility of H2 molecules on B6Be2 and B8Be2 complexes are faithfully demonstrated with the Born-Oppenheimer molecular dynamics (BOMD) simulations. The Be-doped boron nanostructure is a promising candidate for ultra-high hydrogen storage materials.  相似文献   

6.
It is well known that the development of dual-purpose materials is more significant and valuable than single-use materials due to the diversity of their use purposes. Based on density functional theory (DFT), the hydrogen evolution/hydrogen storage characteristics of two-dimensional (2D) B7P2 monolayer are systematically studied in this paper, focusing on the key word of clean energy-“hydrogen”. The results show that the B7P2 monolayer can be used as a stable metal-free decorated catalyst for hydrogen evolution reaction (HER), which is renewable and environmentally friendly. The calculated Gibbs free energy (ΔGH1) is 0.06 eV, which is comparable or even better than that of Pt catalyst (ΔGH1 = ?0.09 eV). In addition, we also found that the increase of hydrogen coverage and strain driving (?2%–2%) did not further enhance the HER activity of B7P2 monolayer, showing a poor ΔGH1. In the aspect of hydrogen storage, we have investigated the hydrogen storage performances of alkali-metal (Li, Na and K) doped B7P2. It is found that in the fully loaded case, B7P2Li6 is a promising hydrogen storage material with a 7.5 wt% H2 content and 0.15 eV/H2 average hydrogen adsorption energy (Eave). Moreover, ab initio molecular dynamics (AIMD) calculations show that there is no dynamic barrier for H2 desorption of Li-decorated B7P2 monolayer. In conclusion, our results indicate that the B7P2 monolayer is not only an excellent catalyst for HER, but also a promising hydrogen storage medium.  相似文献   

7.
The demand for clean renewable energy is urgent in current. The hydrogen application is difficult mainly due to the ratively low capacity in the storage medium. In this work, the adsorption and desorption of the hydrogen molecules by the Li atoms decorated B38 cage are studied by the density functional theory. The calculated largest binding energy of one Li atom (2.68 eV and 2.58 eV) is upon the hexagonal hole of the B38 cage, which is much larger than the experimental cohesive energy of bulk Li (1.63 eV). Each Li atom in the outside of the B38 cage can adsorb up to four H2 molecules. The Ead of B38(Li-nH2)4 decreases from the 0.22 eV for n = 1 to the 0.11 eV for n = 4. The B38(Li–4H2)4 structure achieves the 6.85 wt% hydrogen gravimetric density, which is higher than the goal of 5.5 wt% before 2017 set by the United States Department of Energy. The almost the same partial density of states for the fifth H2 molecule as that of the isolated H2 molecule, the longer 4.5 Å distance between the fifth H2 molecule and the Li atom, together with the small NBO charges all reveal the weak electronic field around the Li+, which can interpret the weak H2 adsorption mechanism. Finally, the B38Li4 structure can easily release 9H2 molecules at 373 K known from the molecular dynamic simulation and practically trap about 1.08H2 molecules at 373 K/3 atom condition calculated by the grand partition function. Thus, its reversible practical HGD of B38Li4-14.34H2 is 6.18 wt%, which is almost the same value as the theoretical 6.85 wt% for B38(Li–4H2)4. Our studies will be the strong theory basis for the future application in hydrogen storage material development.  相似文献   

8.
Hydrogen storage properties of Li functionalized B2S honeycomb monolayers are studied using density functional theory calculations. The binding of H2 molecules to the clean B2S sheet proceeds through physisorption. Dispersed Li atoms on the monolayer surface increase both the hydrogen binding energies and the hydrogen storage capacities significantly. Additionally, ab initio molecular dynamics calculations show that there is no kinetic barrier during H2 desorption from lithiated B2S. Among the studied B8S4Lix (x = 1, 2, 4, and 12) compounds, the B8S4Li4 is found to be the most promising candidate for hydrogen storage purposes; with a 9.1 wt% H2 content and 0.14 eV/H2 average hydrogen binding energy. Furthermore, a detailed analysis of the electronic properties of the B8S4Li4 compound before and after H2 molecule adsorption confirms that the interactions between Li and H2 molecules are of electrostatic nature.  相似文献   

9.
The capability of Li-decorated (AlN)n (n = 12, 24, 36) nanocages for hydrogen storage has been studied by using density functional theory (DFT) with the generalized gradient approximation (GGA). It is found that each Al atom is capable of binding one H2 molecule up to a gravimetric density of hydrogen storage of 4.7 wt% with an average binding energy of 0.189, 0.154, and 0.144 eV/H2 in the pristine (AlN)n (n = 12, 24, 36) nanocages, respectively. Further, we find that Li atoms can be preferentially decorated on the top of N atoms in (AlN)n (n = 12, 24, 36) nanocages without clustering, and up to two H2 molecules can bind to each Li atom with an average binding energy of 0.145, 0.154, 0.102 eV/H2 in the Lin(AlN)n (n = 12, 24, 36) nanocages, respectively. Both the polarization of the H2 molecules and the hybridization of the Li-2p orbitals with the H-s orbitals contribute to the H2 adsorption on the Li atoms. Thus, the Li-decorated (AlN)n (n = 12, 24, 36) nanocages can store hydrogen up to 7.7 wt%, approaching the U.S. Department of Energy (DOE) target of 9 wt% by the year 2015, and the average binding energies of H2 molecules lying in the range of 0.1–0.2 eV/H2 are favorable for the reversible hydrogen adsorption/desorption at ambient conditions. It is also pointed out that when allowed to interact with each other, the agglomeration of Li-decorated (AlN)n nanocages would lower the hydrogen storage capacity.  相似文献   

10.
This work explored the feasibility of Li decoration on the B4CN3 monolayer for hydrogen (H2) storage performance using first-principles calculations. The results of density functional theory (DFT) calculations showed that each Li atom decorated on the B4CN3 monolayer can physically adsorb four H2 molecules with an average adsorption energy of ?0.23 eV/H2, and the corresponding theoretical gravimetric density could reach as high as 12.7 wt%. Moreover, the H2 desorption behaviors of Li-decorated B4CN3 monolayer at temperatures of 100, 200, 300 and 400 K were simulated via molecular dynamics (MD) methods. The results showed that the structure was stable within the prescribed temperature range, and a large amount of H2 could be released at 300 K, indicative of the reversibility of hydrogen storage. The above findings demonstrate that the Li-decorated B4CN3 monolayer can serve as a favorable candidate material for high-capacity reversible hydrogen storage application.  相似文献   

11.
Al-decorated carbon nanotube as the molecular hydrogen storage medium   总被引:1,自引:0,他引:1  
Al-decorated, single-walled carbon nanotube has been investigated for hydrogen storage applications by using Density Functional Theory (DFT) based calculations. Single Al atom-decorated on (8,0) CNT adsorbs upto six H2 molecules with a binding energy of 0.201 eV/H2. Uniform decoration of Al atom is considered for hydrogen adsorption. The first Al atom has a binding energy of 1.98 eV on (8,0) CNT and it decreases to 1.33 eV/Al and 0.922 eV/Al respectively, when the number of Al atoms is increased to four and eight. Each Al atom in (8,0) CNT-8Al adsorbs four H2 molecules, without clustering of Al atoms, and the storage capacity reaches to 6.15 wt%. This gravimetric storage capacity is higher than the revised 2015 target of U.S Department of Energy (DOE). The average adsorption binding energy of H2 in (8,0) CNT-8(Al+4H2), i.e. 0.214 eV/H2, lies between 0.20 and 0.60 eV/H2 which is required for adsorbing and desorbing H2 molecules at near ambient conditions. Thus, Al-decorated (8,0) CNT is proposed as a good hydrogen storage medium which could be useful for onboard automobile applications, at near ambient conditions.  相似文献   

12.
In this study, using the first principles calculation and analysis, we found that the B-doping in double-vacancy defective graphene could effectively increase the binding energy of Ti atoms in each adsorption site, especially in the H2 adsorption site with a maximum binding energy of 8.3 eV. However, N-doped bilayer graphene (N-BLG) reduced the binding energy of Ti atoms by 88% of the adsorption sites. Given these two findings, a B- and N-doped bilayer double-vacancy-defective graphene (Ti-BDVG(Ti)-Ti) was constructed. Our findings also showed that the Ti-BDVG(Ti)-Ti outer surface and inner surface could adsorb 32 and 12H2 molecules, respectively, of which 22, 20 and 2H2 molecules are adsorbed by Kubas, electrostatic interactions and chemisorption, respectively. The hydrogen storage mechanism of Ti-BDVG(Ti)-Ti involves multiple adsorption modes, and this hydrogen storage mechanism provides a theoretical basis for the rational design of hydrogen storage materials with maximum effective hydrogen storage capacity.  相似文献   

13.
The hydrogen storage capacities of a sandwich-type ethylene dimetallocene complex (Cp2Ti2C2H4) are studied using first-principles calculations. It is found that the TiC2H4Ti molecule can intercalate into the two cyclopentadienyl (Cp) rings and form a stable sandwich-type complex. Each Ti atom can adsorb a maximum of three H2 molecules, which corresponds to a gravimetric storage capacity of 4.73 wt%. This hydrogen storage capacity is close to the 2015 target of 5.5% set by the US Department of Energy (DOE) in 2009. Furthermore, the Cp2Ti2C2H4 molecule proposed in this paper is favorable for both adsorption and desorption of hydrogen molecules at room temperature and ambient pressure because its average binding energy of 0.34 eV/H2.  相似文献   

14.
Two-dimensional (2D) B2O monolayer is considered as a potential hydrogen storage material owing to its lower mass density and high surface-to-volume ratio. The binding between H2 molecules and B2O monolayer proceeds through physisorption and the interaction is very weak, it is important to improve it through appropriate materials design. In this work, based on density functional theory (DFT) calculations, we have investigated the hydrogen storage properties of Lithium (Li) functionalized B2O monolayer. The B2O monolayer decorated by Li atoms can effectively improve the hydrogen storage capacity. It is found that each Li atom on B2O monolayer can adsorb up to four H2 molecules with a desirable average adsorption energy (Eave) of 0.18 eV/H2. In the case of fully loaded, forming B32O16Li9H72 compound, the hydrogen storage density is up to 9.8 wt%. Additionally, ab initio molecular dynamics (AIMD) calculations results show that Li-decorated B2O monolayer has good reversible adsorption performance for H2 molecules. Furthermore, the Bader charge and density of states (DOS) analysis demonstrate H2 molecules are physically absorbed on the Li atoms via the electrostatic interactions. This study suggests that Li-decorated B2O monolayer can be a promising hydrogen storage material.  相似文献   

15.
H2 storage capabilities of penta-octa-graphene (POG) adorned by lightweight alkali metals (Li, Na, K), alkali earth metals (Be, Mg, Ca) and transition metals (Sc, Ti, V, Cr, Mn) are studied by density functional theory. Metals considered, with the exception of Be and Mg, can be stably adsorbed to POG, effectively avoiding metal clustering. The average H2 adsorption energies are calculated in a range from 0.14 to 0.95 eV for Li (Na, K, Ca, Sc, Ti, V, Cr, Mn) decorated POG. Because the H2 adsorption energies for reversible physical adsorption lie in the range of 0.15–0.60 eV and the desorption temperatures fall in the range of 233–333 K under the delivery pressure, 4Li@POG and 2Ti@POG are found to be the most suitable for H2 storage at ambient temperature. By polarization and hybridization mechanisms, up to 3 and 5 hydrogen molecules are stably adsorbed around each Li and Ti, respectively. The H2 gravimetric densities can reach up to 9.9 wt% and 6.5 wt% for Li and Ti decorated POG, respectively. Our findings suggest that, with metal decoration, such a novel two-dimensional carbon-based structure could be a promising medium for H2 storage.  相似文献   

16.
For an envisioned hydrogen (H2) economy, the design of new multifunctional two-dimensional (2D) materials have been a subject of intense research for the last several decades. Here, we report the thriving H2 storage capacity of 2D nitrogenated holey graphene (C2N), functionalized with Tin (n = 1–5) clusters. By using spin polarized density functional theory (DFT) calculations implemented with the van der Waals corrections, the most favourable adsorption site for the Tin clusters on C2N has been revealed. With the monomer Ti, the functionalization was evenly covered on C2N having 5% doping concentration (C2N–Ti). For C2N–Ti sheet, Ti binds to C2N with a strong binding energy of ~6 eV per Ti which is robust enough to hinder any Ti–Ti clustering. Bader charge analysis reveals that the Tin clusters donate significant charges to C2N sheet and become cationic to polarize the H2 molecules, thus act as efficient anchoring agents to adhere multiple H2 molecules. Each Ti in C2N–Ti could adsorb a maximum of 10H2 molecules, with the adsorption energies in the range of ?0.2 to ?0.4 eV per H2 molecule, resulting into a high H2 storage capacity of 6.8 wt%, which is promising for practical H2 storage applications at room temperature. Furthermore, Tim (m = 2, 3, 4, 5) clusters have been selectively decorated over C2N. However, with Tim functionalization H2 storage capacities fall short of the desirable range due to large molecular weights of the systems. In addition, the H2 desorption mechanism at different conditions of pressure and temperature were also studied by means of thermodynamic analysis that further reinforce the potential of C2N–Ti as an efficient H2 storage material.  相似文献   

17.
Herein, the hydrogen storage competency of vanadium-decorated biphenylene (Bi+V) has been investigated using Density Functional Theory simulations. The metal atom interacts with biphenylene with a binding energy value of −2.49 eV because of charge transfer between V 3d and C 2p orbitals. The structure and electronic properties are studied in terms of adsorption energy values, the spin-polarized partial density of states (PDOS), band structure plots, and charge transfer analysis. The Kubas-type interactions lead to average hydrogen adsorption energy values of −0.51 eV/H2 which fulfills DOE-US criteria (0.2–0.7 eV/H2). The diffusion energy barrier value of 1.75 eV lowers the chances of metal clustering. The complex binds 5H2 on each V-atom resulting in a storage capacity of 7.52 wt% with an average desorption temperature of 595.96 K. The ab-initio molecular dynamics (AIMD) and phonon dispersions validates structural integrity at higher temperatures suggesting the excellent storage properties of this material at room temperature.  相似文献   

18.
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   

19.
The hydrogen storage capacity of Ti-acetylene (C2H2Ti) and Li-acetylene (C2H2Li) complex has been tested using second order Møller Plesset method with different basis sets. Single Ti(Li) decorated acetylene complex can adsorb maximum of five(four) hydrogen molecules, which corresponds to the gravimetric hydrogen storage capacity of 12(19.65) wt % and it meets the target of 9 wt % by 2015 specified by US Department of Energy. The hydrogen adsorption energies with zero point energy and Gibbs free energy correction show that hydrogen adsorption on C2H2Ti is energetically favourable for a wide range of temperature and that is unfavourable on C2H2Li complex even at a very low temperature. Atom centered density matrix propagation molecular dynamics simulations reveal that four H2 molecules remain adsorbed on C2H2Ti complex at 300 K. Though H2 uptake capacity of C2H2Li complex is higher than that of C2H2Ti complex, the thermochemistry results favour to C2H2Ti complex over C2H2Li complex as a possible hydrogen storage media.  相似文献   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号