Search

With hydrogen contents 6.69 and 7.49 wt%, Sn(AlH 4) 4 and Zr(AlH 4) 4 were experimentally synthesized, but their structures, bonding natures and hydrogen storage properties were not further investigated. This paper determines the low energy structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 crystals by using global optimization algorithm combined with density functional theories, and analyze their electronic structures and bonding properties. The most stable structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 contain isolated H 2 molecules. The formation enthalpies of Zr(AlH 4) 4 reaches 1.0 eV and the value of Sn(AlH 4) 4 is a little smaller. In Zr(AlH 4) 4 , the AlH 5 , AlH 6 and Al 2 H 6 units are connected tightly by Zr atoms through H bridges. In Sn(AlH 4) 4 , the AlH 6 units form a net structure, and the Sn atom exists in SnH 3 with one shared H atom. The bonding characteristics are analyzed by calculating charge populations and crystal orbital hamilton population (COHP). The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. The covalent contributions are close for Sn–H and Al–H bonds but the charge values on the Sn atoms are much smaller. For the Zr–H bonds, both the charges on the Zr atoms and the covalent contributions are smaller than the values of the Al–H bonds. Combining the bonding natures and the structure features, it suggests that proper electronegativity of the metal atoms (Sn and Zr here) is the key factor for the stabilities and reversible hydrogen storage properties of metal aluminum hydrides. • The crystal phases of Sn(AlH 4) 4 and Zr(AlH 4) 4 are predicted. • The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. • In Zr(AlH 4) 4 , Polarized covalent Zr–H bond is weaker than Al–H bond. • Hydrogen storage capacity in Sn(AlH 4) 4 and Zr(AlH 4) 4 reaches 6.69 and 7.49 wt%,respectively. • The electronegativity of metal atoms in aluminum hydrides is related to structural stability and reversible hydrogen storage. [ABSTRACT FROM AUTHOR]

Group IIIA elements are electron deficient, and the transition metal doped clusters can be used to build cluster-based materials. This paper study the global lowest energy structures of In8FeNan (n = 0, 2, 4, 6, 8) by using evolutionary algorithm combined with spin polarized density functional theories. The electronic structures show that the Na atoms donate electrons to the In8Fe core and combine on the peripheries of the clusters through electrostatic interactions. Analyses on density of states and molecular orbitals reveal that the 5s orbitals of In atoms do not mix with other atomic orbitals and form superatomic orbitals with lower energies. The 3d orbitals of Fe atom interact strongly with the superatomic orbitals formed by In 5p. Different interaction patterns compete and it makes the lowest electronic ground states be singlet or triplet. In the triplet states of In8FeNan, the α orbitals have three or four 3d orbitals localized on the Fe atom. For the singlet states, there exists no pure 3d atomic orbitals and the upper valence states show obvious features of bonding or antibonding interactions between atomic Fe 3d and superatomic orbitals composed of In 5p. The strong orbital interactions enhance significantly the stabilities of the clusters. [ABSTRACT FROM AUTHOR]

Stepwise hydrogenated Mg10H2n and Mg9NiH2n are used to study the Ni-doping effect on the hydrogen storage properties of nanoscale MgH2. Global lowest energy structures of the clusters are determined by using evolutionary algorithm combined with density functional theories. The results show that Ni-doping enhances significantly the thermal stabilities of the metal clusters and Mg9NiH2n species. H atoms in Mg9NiH2n bind preferentially with Mg atoms and H atoms begin to bind on the Ni atom at Mg9NiH12. The binding strengths of H atoms in Mg10H2n and Mg9NiH2n clusters increase monotonically with the hydrogenation ratios until the hydrogenation gets saturated. At lower hydrogenation degrees, the binding of H atoms are relatively weaker. At higher hydrogenation ratios, the calculated dehydrogenation barriers show that the dissociation of the H–H pairs bound on the Ni–Mg atoms is obviously easier than the dissociation of the H atoms bound on the Mg atoms. [ABSTRACT FROM AUTHOR]

Atomic gallium has nearly identical ionization energy with aluminum but its bulk is composed of covalent-bound Ga2 dimers. The bonding nature in gallium clusters is still controversial. This paper investigates the geometries, stabilities, and bonding natures of GanLim (n = 4–15, m = 0, 1, 2) using evolutionary algorithm coupled with density functional theory (DFT) calculations. The alkaline atoms act mainly as electron donors. The results indicate that the lowest-energy structures of gallium clusters are quite different to the corresponding aluminum clusters, but Ga6Li2 and Ga13Li demonstrate enhanced thermal and chemical stabilities and their electronic structures are in good accordance with the prediction of the jellium model. Quantitative evaluation of the covalent contributions based on crystal orbital Hamilton population (COHP) analysis suggests that there are stronger covalent interactions than in aluminum clusters. The bonding in gallium clusters is of primarily metallic nature but the covalent interactions affect the geometric structures. [ABSTRACT FROM AUTHOR]

The hydrogen adsorption on B16N16 clusters decorated by Li atoms is studied by density functional theory calculations. Li atoms transfer their electrons to the B atoms in B16N16 and form Li+ cations. The charges on Li are larger than 0.8 e. The hydrogen molecules are moderately polarized and adsorbed on the Li+ ions. The results indicate that each Li atom can adsorb two H2 molecules with an adsorption energy of about 0.16 eV/H2. The gravimetric hydrogen density can reach 9.15 wt% when B16N16Li12 adsorbs 24 H2. The present calculation results are helpful for exploring reversible hydrogen storage materials with high recycling storage capacity at ambient conditions. [ABSTRACT FROM AUTHOR]

Developing an efficient storage medium is a substantial challenge for the utilization of hydrogen as an energy carrier, and designing materials with intermediate holding strength for hydrogen is the key to the solution. In this paper, we decorate h-BN using superalkali NLi4 and investigate the hydrogen storage properties by density functional theory. NLi4 clusters can be anchored stably on BN sheets with a binding energy −1.43 eV. As the NLi4 species has enhanced stability, decoration using the superalkali effectively improves the aggregation of the metal atoms on a substrate. Replacing alkali metal atoms by superalkalis also offers more spaces for H2 adsorption. The H2 molecules adsorbed on the bottom Li+ cations are strongly polarized due to the small radius of Li+, and the H2 molecules attached to the top Li+ are adsorbed by feeding back the excess electron up to the antibonding σ* orbitals of the H2 molecules. Each NLi4 can absorb nine H2 molecules with adsorption energies about −0.20 eV/H2. The adsorption strengths fall in the ideal window for reversible uptake-release at ambient temperatures. The hydrogen storage capacity at the decoration density of NLi4/BN = 1:6 reaches 9.40 wt. %. The present study suggests that NLi4 decorated 2D materials can be potential candidates for hydrogen storage at room temperature. [ABSTRACT FROM AUTHOR]

Al–Si alloys have excellent properties for building engine blocks, and their microstructures have important effect on the performance. Investigations on the electronic structures of Al–Si clusters help to understand the microstructural evolution and improve the properties of the alloys. This paper studies the geometric structures, stabilities and bonding features of AlnSim (n,m = 2,4,6 and n + m = 8,10,12) clusters by using genetic algorithm combined with density functional theory and QCISD models. The results show there are a lot of isomers with close energies, and the geometric structures suggest no obvious Al–Si segregation. The electronic structures of the Al–Si clusters are similar to the metal clusters; the density of states of the aluminum-rich clusters agrees with the jellium shells. Doping silicon enhances the stabilities of the aluminum clusters significantly; the binding energies increase considerably with the Si/Al ratios. The bonding features and energetics demonstrate the Si–Si and Si–Al interactions are much stronger than the Al–Al interaction. As the dispersion of Si atoms will form more Si–Al bonds, it suggests the silicon atoms can form highly dispersed states in the hypoeutectic and eutectic alloys (≤ 12.6% Si). [ABSTRACT FROM AUTHOR]

Hydrogen in alanates forms AlH4− unit and the bonding strength depends on the electron donor property of the metal atoms. The electronic structures of Al─Si clusters are similar to metal clusters but the Al atom is a weaker electron donor than that in light metal alanates, so hydrogen may form weaker Al─H bonds in Al─Si systems. This article studies the adsorption and dissociation of H2 on Al4Sim (m = 2, 3, and 4) clusters by using density functional theory. The physisorption of H2 molecules on Al4Sim is very weak, the average binding energies of two H atoms on Al4Sim fall in the range –0.61 to –1.50 eV. It suggests that Al─Si hydrides can be candidates for hydrogen storage at ambient conditions. The investigation on the H2 dissociation processes shows that the lowest energy barrier is 0.76 eV, which implies that H2 dissociation can occur at moderate temperatures. [ABSTRACT FROM AUTHOR]

The low-energy structures of Al n Mg m (n = 4–8, m = 1–3) are determined by using the genetic algorithm coupled with a modified embedded-atom interatomic potential. The close-packed structures are preferable in energy for Al-Mg clusters and in most cases there exist a few isomers with close energies. The stabilities of the Al-Mg clusters are governed by Mg/Al ratios and the electronic configurations. The clusters with lower Mg/Al ratios are more stable. The valence molecular orbitals and the density of states consistently demonstrate that the electronic structures of Al-Mg clusters can be described by the jellium model but the 2S level interweaves with the 1D levels. Al 6 Mg corresponds to a magic number structure with pronounced stability and large energy gap; the 20 valence electrons form closed 1S 2 1P 6 1D 10 2S 2 shells. Natural bond orbital analysis indicates that magnesium transfer electrons to aluminum; the average charge on Mg atoms is 0.61, but the charge on Al atoms depends strongly on the number of the connected Mg atoms. [ABSTRACT FROM AUTHOR]

The low-energy structures of Al8Sim(m= 1–6) have been determined by using the genetic algorithm combined with density functional theory and the Second-order Moller-Plesset perturbation theory (MP2) models. The results show that the close-packed structures are preferable in energy for Al–Si clusters and in most cases there exist a few isomers with close energies. The valence molecular orbitals, the orbital level structures and the electron localisation function (ELF) consistently demonstrate that the electronic structures of Al–Si clusters can be described by the jellium model. Al8Si4corresponds to a magic number structure with pronounced stability and large energy gap; the 40 valence electrons form closed 1S21P61D102S21F142P6shells. The ELF attractors also suggest weak covalent Si–Si, Si–Al and Al–Al bonding, and doping Si in aluminium clusters promotes the covalent interaction between Al atoms. [ABSTRACT FROM AUTHOR]

The spherical jellium model predicts that metal clusters having 18 and 20 valence electrons correspond to the magic numbers and will show specific stabilities. We explore in detail the geometric structures, stabilities and electronic structures of Al-Mg clusters containing 18 and 20 valence electrons by using genetic algorithm combined with density functional theories. The stabilities of the clusters are governed by the electronic configurations and Mg/Al ratios. The clusters with lower Mg/Al ratios are more stable. The molecular orbitals accord with the shell structures predicted by the jellium model but the 2S level interweaves with the 1D levels and the 2S and 1D orbitals form a subgroup. The clusters having 20 valence electrons form closed 1S1P1D2S shells and show enhanced stability. The Al-Mg clusters with a valence electron count of 18 do not form closed shells because one 1D orbital is unoccupied. The ionization potential and electron affinity are closely related to the electronic configurations; their values are determined by the subgroups the HOMO or LUMO belong to. Graphical abstract: [ABSTRACT FROM AUTHOR]

Using density functional theory, we investigate hydrogen adsorption on Li-coated B 36 N 24 clusters. It is found that the preferred binding sites for Li atoms are the hexagonal B 4 N 2 and pentagonal B 3 N 2 rings. The interaction of Li atoms with the cluster is stronger than that among Li atoms. The clustering of Li atoms is avoided. The coated Li atoms are positively charged and the H 2 molecules are polarized when they approach the Li atoms. Each Li atom in the Li-coated B 36 N 24 complexes can adsorb two H 2 molecules. The average adsorption energies are in the range of −0.08 to −0.16 eV/H 2 . The fully coated B 36 N 24 Li 24 can hold up to 48 H 2 with an average adsorption energy of −0.09 eV/H 2 , corresponding to a hydrogen uptake of 9.7 wt%. [ABSTRACT FROM AUTHOR]

Single-layer blue phosphorus (SLBP) has displayed charming photoelectric performances, but its property in hydrogen storage is not outstanding due to the weak interactions. To expand the application of SLBP in hydrogen storage, we attempt to screen SLBP-based materials with stable structures and strong polarity using density functional theory by doping lightweight elements and grafting alkali metal atoms. The simulation results indicate that the lightweight elements (B, C, N, O and F) doped SLBP systems have more stable structures due to the strong orbital interaction than pure SLBP, and exhibit electron deficient characteristics. Compared to the pure SLBP, the H 2 adsorption energies of the doped systems improve and range from 0.05 to 0.09 eV, but it still cannot meet the requirements of ideal hydrogen storage. Therefore, the lightweight element doped SLBP systems are further grafted by Li atom. Under the synergistic effect of doping lightweight elements and grafting Li atoms, H 2 molecules are strongly polarized, and the corresponding adsorption energies of H 2 reach to 0.16, 0.26, 0.28, 0.30, and 0.10 eV, respectively. It is worth emphasizing in the C-doped SLBP system that the hydrogen storage capacity of reaches 5.53 wt% for each Li atom adsorbs one hydrogen molecule and the corresponding adsorption energy is 0.23 eV/H 2 when the ratio of C to P atoms increases to 6:26. For each Li atom adsorbs two hydrogen molecules in the same hydrogen storage system, the hydrogen storage capacity reaches 10.48 wt% with 0.18 eV/H 2 adsorption energy. We hope these results can provide theoretical basis and scientific guidance for searching for SLBP-based materials with excellent hydrogen storage performances at ambient temperature. [ABSTRACT FROM AUTHOR]

Hydrogen storage properties of Li-decorated graphene oxides containing epoxy and hydroxyl groups are studied by using density functional theory. The Li atoms form Li 4 O/Li 3 OH clusters and are anchored strongly on the graphene surface with binding energies of −3.20 and −2.84 eV. The clusters transfer electrons to the graphene substrate, and the Li atoms exist as Li+ cations with strong adsorption ability for H 2 molecules. Each Li atom can adsorb at least 2H 2 molecules with adsorption energies greater than −0.20 eV/H 2. The hydrogen storage properties of Li-decorated graphene at different oxidation degrees are studied. The computations show that the adsorption energy of H 2 is −0.22 eV/H 2 and the hydrogen storage capacity is 6.04 wt% at the oxidation ratio O/C = 1/16. When the O/C ratio is 1:8, the storage capacity reaches 10.26 wt% and the adsorption energy is −0.15 eV/H 2. These results suggest that reversible hydrogen storage with high recycling capacities at ambient temperature can be realized through light-metal decoration on reduced graphene oxides. Image 1 • H 2 storage and electrical properties of Li-decorated RGO are researched using DFT. • Li 4 O/Li 3 OH anchored on graphene surface with binding energies of −3.20 and −2.84 eV. • Each Li adsorbs at least 2H 2 with adsorption energies greater than −0.20 eV/H 2. • Oxidation ratio O/C = 1/16 possess −0.22 eV/H 2 E ad and 6.04 wt% H 2 storage capacity. • O/C = 1:8, the storage capacity reaches 10.26 wt% and the E ad is −0.15 eV/H 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adsorption energies of CO 2 on the surface oxygen vacancies of different crystalline In 2 O 3 were calculated using DFT. • The effect of the spatial distributions of two active components on the CO 2 hydrogenation to aromatics was studied. • The acidity of catalyst under different spatial distributions was studied through NH 3 -TPD. In tandem catalysts, not only good synergy between the two active components is required, but also the precise control of the spatial distribution between the two active components of metal oxides and zeolite is crucial for the migration and conversion of reaction intermediates in the direct conversion of CO 2 to hydrocarbons. The correlation between the metal and the acidic site of zeolite has traditionally been simplified as "the closer, the better". However, it should be noted that this principle only holds true for a portion of tandem catalysts. Therefore, this paper studied the effect of different crystalline In 2 O 3 (cubic phase, hexagonal phase, and mixed cubic/hexagonal phase) and sheet HZSM-5 zeolite tandem catalysts on the activity of CO 2 hydrogenation reaction under different spatial distribution. The generalized gradient approximation (GGA) of density functional theory (DFT) were used to simulate the adsorption energy of CO 2 by oxygen vacancy on c-In 2 O 3 (1 1 1) and h-In 2 O 3 (1 0 4) planes, it was found that O v1 on c-In 2 O 3 (1 1 1) and O v4 on h-In 2 O 3 (1 0 4) had the strongest adsorption energy for CO 2. In addition, it has been observed that the proximity of the two active components (e.g., during mortar mixing) results in decreased catalytic performance. This is due to the migration of metal In, which neutralizes the acid sites of zeolites and leads to inefficient conversion of methanol reaction intermediates to aromatics. As a result, CO 2 conversion and aromatic selectivity are decreased. [ABSTRACT FROM AUTHOR]

• The deformation coefficients δ and ε of geometric structures are approximately equal to 1.0 at the 40 valence electrons count. The geometric structures of Al-Cu clusters are spherical when the numbers of the valence electrons around the magic number 40, otherwise the geometric structures of cluster are oblate or prolate. • The stabilities of Al-Cu clusters relate to the Cu/Al ratios and the electronic configurations. Doping Cu atoms in the Al n clusters weakens the stability of the clusters. However, the Al 13 Cu, Al 13 Cu 2 and Al 12 Cu 3 clusters with 40, 41 and 39 valence electrons possess higher stability. • In Al 13 Cu cluster, the 3d orbitals of the central Cu atom interact strongly with the superatomic 1D orbitals of the cluster and formed five bonding orbitals and five antibonding orbitals. • Including ten 3d electrons of Cu atom, "50 valence electrons" in Al 13 Cu cluster formed 1S21P63d101D102S21F142P6 closed shell and the molecular orbitals accord with the shell structures predicted by the Jellium model. The 3d electrons of Cu atom don't affect the Jellium model of the cluster. The properties of Al n Cu m (n = 10–15, m = 1–3) clusters are explored using genetic algorithm combined with density functional theory (GA-DFT). The geometric structures of Al-Cu binary clusters are spherical when the numbers of the valence electrons are around the magic number 40 predicted by Jellium model. The stabilities decrease as the number of doping Cu atom increases. The stabilities also relate to the electronic configurations. In Al 13 Cu-a cluster, the 3d orbitals of the central Cu atom interact strongly with the superatomic 1D orbitals and formed five bonding orbitals and five antibonding orbitals. The bonding orbitals are dominated by 3d orbitals of Cu, and antibonding orbitals are composed mainly of the superatomic 1D orbitals. The "50 valence electrons" (including 3d10 of Cu) form closed 1S21P63d101D102S21F142P6 shells, and this electronic configuration can be taken as the combination of 40-electron rule. The 3d electrons of Cu atom don't affect the Jellium model of the cluster. [ABSTRACT FROM AUTHOR]

Abstract: Density functional theory and time-dependent density functional theory with hybrid functional B3LYP are employed to investigate several physical and chemical properties of N-methyle-3,4-fulleropyrrolidine (NMFP), including geometry, electron population, infrared (IR), Raman and electronic absorption spectra. The analysis of the natural bond orbital (NBO) suggests that there are about 0.16 electrons transferred from the moiety –C3NH7 of NMFP to fullerene cage. The strongest IR and Raman spectra are from different modes with frequencies of 2955 and 1490cm−1, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant and hyperpolarizability are 521.6, 65.3 and −68 (a.u.), respectively. The calculated electronic absorption spectra agree well with the experimental measurement. The solvent cyclohexane did not significantly affect the overall spectral shape but the absorption intensity and low-energy-band locations. The first absorption band in visible region comes from transitions, and the bands near 437 and 451 nm are both related to the ligand-to-fullerene charge transfer processes. The second absorption band in near-UV region is dominated by typical transitions. [Copyright &y& Elsevier]

The stabilities and electronic structures of Si m Al n-m N n and Si n N n (n = 16, 20, m = 12 and n = 24, m = 16) fullerene-like cages have been investigated using density functional method B3LYP and the second-order perturbation theory MP2. The results show that the Si m Al n-m N n and Si n N n fullerenes are more stable than the AlN counterparts. Comparing with the corresponding Al n N n cages, one silicon atom in each Si 2 N 2 square protrudes and the excess electrons reside as lone pair electrons at the outside of the protrudent Si atoms. Analyses on the electronic structures suggest that the Si N bonds are covalent bonding with strong polarity. The ELF (electron localization function) shows large electron pair probability between Si and N atoms. The orbital interactions between Si and N are stronger than that between Al and N atoms; the overlap integral is 0.40 per Si N bond in Si n N n and 0.34 per Al N bond in Al n N n . The AIM (atoms in molecule) charges on the Al atoms in Al n N n and Si m Al n-m N n are 2.37 and 2.40. The charges on the in-plane and protrudent Si atoms are about 2.88 and 1.50 respectively. Considering the large local dipole moments around the protrudent Si atoms, the electrostatic interactions are also favorable to the SiN cages. [ABSTRACT FROM AUTHOR]

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 sp 3 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. H 2 molecules adsorbed on the Li + cations are strongly polarized and form strong adsorption. When two H 2 are adsorbed on each Li atom decorated at the 1:1 Li/P ratio, the hydrogen storage capacity reaches 9.52 wt% but the H 2 molecules are arranged in two layers with the adsorption energy −0.168 eV/H 2 . When the Li atoms are decorated alternatively on the two sides of the P 6 rings with a Li/P ratio of 1:2, each Li atom can absorb two H 2 molecules in a single–layer; the hydrogen storage capacity is 5.48 wt% and the adsorption energy reaches −0.227 eV/H 2 . These results mean the Li–decorated SLBP can work at ambient temperature with high reversible hydrogen storage capacity. [ABSTRACT FROM AUTHOR]

• Palygorskite-based HZSM-5 zeolite was prepared by hydrothermal method. • Zn-UIO-66/(HZSM-5)-palygorskite catalyst showed excellent catalytic performance. • The CO 2 adsorption performance over the Zn-UIO-66 system was simulated by DFT. • Hydrogenation of CO 2 to aromatics follows the methanol-mediated pathway. Palygorskite-based HZSM-5 zeolite was prepared through the hydrothermal method using acidified palygorskite as the Si source and supporter. A series tandem composite of M (Zn, Ga, In)-UIO-66/(HZSM-5)-palygorskite was obtained using metal–organic frameworks (UIO-66) as the carrier using the physical mixing method. XRD, SEM, TEM, N 2 adsorption–desorption, NH 3 -TPD, Py-IR, H 2 -TPR, XPS, and CO 2 -TPD were used to investigate the composite's physical and chemical properties. The calcination temperature effect of palygorskite-based HZSM-5 zeolite, Zn to Zr mole ratio, the space distance between Zn-UIO-66 and palygorskite-based HZSM-5 zeolite, and reaction conditions on the catalytic performance of CO 2 hydrogenation to aromatics were investigated. Zn-UIO-66/(HZSM-5)-palygorskite showed excellent catalytic performance. CO 2 conversion was 21.2% and selectivity for benzene, toluene, and xylene (BTX) were 84.9% under optimal reaction conditions. In situ DRIFTS and Density Functional Theory (DFT) were used to investigate and simulate the CO 2 adsorption performance over the Zn-UIO-66 system. In addition, the reaction mechanism of CO 2 hydrogenation was explored. The transition state and energy barrier for CO 2 hydrogenation to aromatics were obtained by minimum energy search of the LST/QST transition state. [ABSTRACT FROM AUTHOR]

We prepared ZnZr 7 O/HZ-1.5NH 4 F tandem catalyst with high catalytic activity for the direct conversion of CO 2 hydrogenation to aromatics by combining theoretical calculations and experiments. [Display omitted] • It was simulated that the (0 1 0) plane of the sheet HZSM-5 had the strongest adsorption capacity for CH 3 O* and CHOO*. • We prepared catalysts with high catalytic activity and stability by combining theoretical calculations and experiments. • The thickness can be precisely adjusted to prepare a series of sheet HZSM-5 by adding urea and NH 4 F. • Urea inhibits the generation of defective sites in HZSM-5, while NH 4 F promotes the generation of defective sites. • The thickness of the sheet HZSM-5 is also a factor affecting the catalytic activity. The adsorption properties of CH 3 O* and CHOO* adsorbed on the three crystal planes (0 0 1, 0 1 0, 1 0 1) of HZSM-5 were simulated by the generalized gradient approximation (GGA) of density functional theory (DFT), it was found that the (0 1 0) plane corresponding to the b-axis of the sheet HZSM-5 had the strongest adsorption energy for CH 3 O* and CHOO*. Therefore, we successfully synthesized sheet HZSM-5 with different thicknesses by adding the inhibitor (urea) and mineralizer (F−) to the synthesis system based on the theoretical calculations. The physicochemical properties of HZSM-5 were investigated by the characterization methods of SEM, TEM, Py-IR, OH-IR, CO 2 -TPD and so on. The results showed the thickness of HZSM-5 can be precisely adjusted by adding urea and NH 4 F and changing the ratio of urea/NH 4 F or TPAOH/NH 4 F. Then, the sheet HZSM-5 and ZnZr 7 O were connected in tandem to investigate the reaction conditions and catalytic performance for the direct conversion of CO 2 hydrogenation to aromatics. It was found that the HZ-1.5NH 4 F had a large specific surface area, suitable B acid content and more defect sites. These advantages resulted in a high aromatic selectivity of 77.5% and CO 2 conversion of 17.6% over ZnZr 7 O/HZ-1.5NH 4 F. Meanwhile, it exhibits stable performance and no significant deactivation after 80 h of operation. [ABSTRACT FROM AUTHOR]

The adsorption of H 2 on B 24 N 24 , Al 24 N 24 and B 12 Al 12 N 24 clusters is studied by density functional theory calculations. Typical candidate isomers of B 24 N 24 , Al 24 N 24 and B 12 Al 12 N 24 are optimized and the lowest-energy structures are determined. H 2 adsorption on the three lowest-energy structures is investigated. The results show that H 2 is adsorbed on B/Al atoms in the side-on manner and on N atoms in the end-on manner. The adsorption of H 2 on Al sites is much stronger than the adsorption on B sites, and the mixing of B and Al as in B 12 Al 12 N 24 enhances the adsorption of H 2 obviously. After considering van der Waals interactions, the adsorption energies on Al, B and N are about −0.11 to −0.18, −0.05 and −0.04 to −0.06 eV, respectively. Interaction mechanisms between H 2 and the clusters are clarified by analyzing the electronic structures of the adsorption complexes. [ABSTRACT FROM AUTHOR]