Two strategies of decoration by three elements Z = Li, Be and Na in cyclic site, and substitution of Zn by Mg and Cd in unit cell were used in the framework of functional density theory to tune the ...hydrogen storage properties of metal-organic framework-5 (MOF-5) based on Zn whose decomposition temperature and initial gravimetric capacity are 300 K and 1.57 wt% respectively.
Based on the adsorption of hydrogen molecules in the crystal surface at three different adsorption sites with three orientations of H2, we show that our system may reach a maximum gravimetric storage capacity of 4.09 wt% for multiple hydrogen molecules. Moreover, the functionalization of Z combined to the substitution, shows an exceptional improvement of hydrogen storage properties. For example, Mg-MOF-5 decorated with Li2 has a capacity up to 5.41 wt% and 513 K as desorption temperature.
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•New approach to tune MOF-5 hydrogen storage properties.•Li, Be and Na decoration improves the H2 storage capacity of MOF-5.•Zn substitution by Mg and Cd enhances the desorption temperature.•Mg-MOF-5 decorated with Li2 exhibits Cg = 5.41 wt% and Td = 513 K.
•Zn substitution effects on Zn-MOF-5 hydrogen storage properties.•Substitution enhances stability and decomposition temperature of Zn-connector.•Cyclic sites with inclined orientation is the most ...stable adsorbing configuration.•Significant increase in the gravimetric and volumetric capacities is observed.
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As it is known, the high surface area, permanent porosity, tunable pore sizes, rigidity, structural flexibility and thermal stability make MOFs and especially Zn-MOF-5 as promising materials. But the small enthalpy change (heat of adsorption) and its low desorption temperature hinders its use. Heat of adsorption varies with the type of metal, framework topology, surface area, and pore size, and hence the extent of hydrogen adsorption in MOF materials can be influenced by manipulating these parameters. Therefore, a substitution approach is presented in the present work to improve the thermodynamic properties of MOF-5. DFT method is used to investigate the effect of the substitution of Zn by Cd and Mg on structural, thermodynamic and hydrogen storage properties of Zn-MOF-5-connector. Results of calculation show that the formation energy for Zn-connector is greater than that of Cd and Mg connectors which enhances its stability and therefore increases the decomposition temperature to 191.79 and 175.81 K for Mg and Cd connector, respectively. In addition, the adsorption and diffusion of H2 are investigated and discussed. Furthermore, a significant increase in the gravimetric and volumetric capacities from 1.57 wt% and 12.26 g L-1. H2 for Zn based connector to 6.37 wt% and 40.16 g L-1. H2 for Mg-connector is observed.
•The Blue-P/Al2SO vdW heterostructure has been predicted using first-principles calculations.•The Blue-P/Al2SO vdW heterostructure can facilitate the separation of photo-excited electrons and ...holes.•The CB and VB edges cover the standard redox potentials required for water splitting at 1≤pH≤10.•High optical absorption in the visible region for Blue-P/Al2SO vdW heterostructure compared to the individual monolayers.•The present Blue-P/Al2SO vdW heterostructure show optimal photovolatics and photocatalytic performance.
The enhancement of photocatalytic efficiency in monolayer materials receives a substantial boost through the deliberate construction of two-dimensional van der Waals heterostructures. In this work, we introduce a novel two-dimensional Blue-P/Al2SO vdW heterostructure through rigorous first principles calculations. Blue-P/Al2SO forms a type-II heterostructure with an indirect band gap of 1.64 eV (PBE) and 2.35 eV (HSE), and exhibits a large relative ratio (D), which arises from the effective separation of photogenerated electron-hole pairs and preventing their recombination . We have confirmed its dynamic and thermal stability by analyzing the phonon spectrum and conducting ab-initio molecular dynamics simulations at room temperature. The interface generates a built-in electric field that expedites the reorganization of photo-generated holes within Blue-P monolayer and photo-generated electrons within Al2SO monolayer. Crucially, the band edges of this heterostructure covers the water redox potential in a wide range of pH from acidic to basic solution, this provides a positive outlook for experiments aimed at preparing it as a photocatalyst. Furthermore, our investigations reveal that the light-absorption ability of the Blue-P/Al2SO vdW heterostructure is relatively strong. The highest light absorption peak is 3 × 105 cm−1 at 600 nm wavelength. Consequently, this newly designed Blue-P/Al2SO vdW heterostructure exhibits significant potential for applications in solar energy conversion and serves as a promising photocatalyst for facilitating the process of water splitting.
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•YFeO3have been studied with GGA and GGA + U reveal asemi-conductor and an Antiferromagnetic type-G behavior.•Magnetic anisotropy results for both approximations show that easy axis magnetization for ...YFeO3 is along the c-axis.•Computations of the electric polarization and evaluationthe magnetic transition temperature of the orthorhombic YFeO3has done using DFT and Monte Carlo simulation.
In this study, we have thoroughly investigated the electronic, magnetic, and electrical properties of yttrium orthoferrite using density functional theory (DFT) within the generalized gradient approximation (GGA) and the (GGA + U) approach, which incorporates the Hubbard term (U). Both approximations consistently reveal a semiconductor behavior and an antiferromagnetic behavior of type-G between the iron (Fe) ions. To delve deeper into the magnetic interactions within YFeO3, we have proposed a physical model. This model allows us to calculate the magnetic exchange coupling and magnetic anisotropy parameters through DFT calculations. Additionally, we have conducted computations to determine the electric polarization. Our results have shown that the electric polarization in YFeO3 is exclusively derived from electronic polarization. We have also explored the relationship between the direction of electric polarization and the easy-axis magnetization. In our investigation, we found that both the electric polarization and easy-axis magnetization align along the c-axis in both approximations. Furthermore, we have examined the influence of the Hubbard term on the direction of polarization. To assess the magnetic temperature transition, we employed Monte Carlo simulations using the Ising model. The critical temperature, denoted as TN, obtained with the GGA approximation is found to be 726.66 K. Remarkably, this value closely matches the experimental critical temperature when compared to the critical temperature obtained with the GGA + U approximation.
In this paper we have studied the stability, mobility and voltage profile of alkali metal intercalated BC3 monolayer (MxBC3), for 0 < x ≤ 1 and M = Li, Na. Firstly, our calculations have the ...objective to identify the lower energy of Li and Na adsorption sites by using the density functional theory, then we calculate the minor diffusion energies of Na and Li on the surface of BC3 monolayer as shown by the total density of states of MxBC3 (M = Li, Na). Moreover, we showed that BC3 monolayer has changed his semiconductor character to metallic character after the adsorption of Li and Na on his surface. Importantly, we have demonstrated that BC3 monolayer has a higher theoretical capacity (582,63 mA h/g) as compared to Mo2C, VS2, MoS2, and graphite. Finally, we show that monolayer BC3 has a low average open-circuit voltage of 0.48 V for Li and 0.79 V for Na. These results highlight suggest that BC3 monolayer can be a promising anode material both for lithium-ion and sodium-ion batteries.
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•Li/NaBC3 monolayer has changed his semiconductor character to metallic character.•Na adsorbed configurations are more stable than the case of Li in general.•The capacities of Li2BC3 and Na2BC3 are 14102.79 mA h/g and 9227.13 mA h/g.•The diffusion energy of Li/Na, suggesting fast charging/discharging processes.•LixBC3 and NaxBC3 have small variation of voltage.
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•G/P’s semi-metallic behavior converts to a metallic nature after K/Na adsorption.•K/Na diffusion on G/P’s regions are faster and show strong directional anisotropy.•G/P system ...provides a theoretical storage capacity of 433mAh/g and 580mAh/g for Na and K, respectively.•An average potential of 0.29 V (K)/0.58 V (Na) for the G/P nano-heterostructure is ideal for KIBs/NIBs.
Rechargeable Potassium and Sodium-ion batteries started to receive a vast amount of attention in recent years against their Lithium-ion counterparts. However, the development of a high-performing anode material for these ion batteries is still to be explored. In this work, we conduct a first-principles study on the adsorption and diffusion behaviors of Potassium (K) and Sodium (Na) in a Graphene/Phosphorene (G/P) van der Waals nano-heterostructure, in order to assess its suitability as an anode for both K-ion and Na-ion batteries. We investigate the electrochemical properties of the system, including binding energies, band structure, ion diffusivity out-side and in-side the G/P system, as well as the heterostructure’s stability at a high metallic coverage. The calculated binding energies for K and Na are −2.69 eV and −2.42 eV, respectively, which are strong enough to prevent metallic clustering during the cycling. The diffusion of K/Na within G/P’s regions shows strong directional anisotropy with a low diffusion barrier of 0.04 eV for K and 0.05 eV for Na along the zigzag direction. We also observe that the addition of K/Na atoms into the G/P system turns its semi-metallic nature into a metallic one. Moreover, we demonstrate that the intercalation of K/Na atoms within the G/P structure give low operating potentials of approximately 0.29 V for K and 0.58 V for Na. Thus, the nano-heterostructure can provide a theoretical storage capacity of 433 mAh/g and 580 mAh/g respectively for K and Na. Finally, the thermal stability of a fully potassiated/sodiated G/P system at room temperature is revealed by the ab-initio Molecular-Dynamics (AIMD) calculations. Considering all these properties, we conclude that the G/P nano-heterostructure can be considered as a good candidate for negative-electrode-materials for both K- and Na-ion batteries.
The current research focuses on analyzing the magnetic and magnetocaloric properties of REH2(RE=Gd,Tb,Dy) in a CaF2-like face-centered cubic system. Through the application of first-principles ...calculations and Monte Carlo simulations, the following physical parameters are determined: Adiabatic temperature change, isothermal entropy change, and relative cooling power (RCP). The magnetic moments of Gadolinium, Terbium, and Dysprosium calculated by the PWSCF method are 6.76μB, 5.74μB, and 4.65μB respectively, aligning well with experimental results. The compounds underwent a second-order phase transition from antiferromagnetic to paramagnetic at TN=21.7K, 17.6K, and 4.3K respectively for GdH2, TbH2, and DyH2. The isothermal entropy change (−ΔSMmax) reached a maximum value of −11.75J/kg.K, −12.47J/kg.K, and −12.87J/kg.K for GdH2, TbH2, and DyH2 under a magnetic field of 5T. We found also that the hydrogenation of rare earth reduces its magnetic performance while but it enhances its thermodynamic and mechanical stability.
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•The thermodynamic and mechanical stability of REH2(RE=Gd,Tb,Dy) compounds are investigated.•The REH2 compounds are metals with an antiferromagnetic state.•The magnetocaloric property values of REH2 compounds indicate that they are potential for low-temperature magnetic refrigeration applications.•Comparing the properties of Gd with REH2 compounds reveals the role of hydrogen in these materials.
Black phosphorus (BP) has recently been regarded as a promising anode for sodium-ion batteries (SIBs) owing to its high storage capacity, rapid Na mobility in its lamellar structure, and low redox ...potential. However, its poor cyclability due to structural instability hampers its further implementation in SIBs. Here, we propose to design a novel two-dimensional nanocomposite by vertically stacking a C6BN sheet on a black phosphorene layer (C6BN/Black-Pn). Atomistic simulations by the van der Waals corrected density functional theory method were conducted to assess the suitability of the designed C6BN/Black-Pn model as a potential anode in SIBs. Benefiting from C6BN's electronic and chemical features, Black-Pn's band gap in C6BN/Black-Pn is diminished to 0.14 eV, which disappears and indicates metallic character upon sodiation. Additionally, the optimized Na adsorption energy within the nanocomposite is decreased to −2.06 eV, compared to −1.76 eV in pure Black-Pn and −0.98 eV in C6BN, with a modest diffusion barrier of 0.23 eV. A maximal theoretical capacity of 568.77 mAh/g and a low potential of 0.48 V are predicted for the nanocomposite. The above evaluation of C6BN/Black-Pn electrode for SIBs may provide better insights into adopting a physical approach to address BP electrochemical failures for advanced energy storage.
With the incorporation of a rigid C6BN layer, the C6BN/Black-Pn nanocomposite possesses superior electrochemical performance, featuring high specific capacity, low open-circuit voltage, and a moderate Na diffusion barrier, positioning it as a promising anode material for sodium-ion batteries. Display omitted
•The design of C6BN/Black-Pn as an anode in NIBs is evaluated using DFT and AIMD.•Thermal and kinetic stability, coupled with adequate formation energy, are shown.•Improved electronic behavior is observed in C6BN/Black-Pn.•A high capacity of 568.77 mAh/g and a low energy barrier of 0.23 eV are revealed.•Low average voltage of C6BN/Black-Pn is predicted.
Recently, a lateral heterostructure (LHS) combining black phosphorene and graphene edges was developed, addressing volume change issues and enhancing capacity retention. However, unresolved geometric ...concerns require further investigation, particularly regarding its suitability as a sodium-ion battery (SIB) anode. We present three LHSs models, labeled (LHS PC)1, (LHS PC)2, and P5C6, all featuring edge contact symmetry (armchair direction) but with different interface defects. Through first-principles calculations, we compare their structural stability, electronic properties, and charge transfer mechanisms. P5C6 exhibits superior energetic stability and dynamic stability, with type II band alignment and a 0.73 eV direct band gap, indicating optimal charge diffusion. Electrochemical assessments reveal a low sodium migration barrier (0.019 eV), facilitating rapid charge-discharge rates, with a storage capacity of 590.5 mAh/g and intercalation at a low average voltage (0.27 V). Additionally, ab initio molecular dynamics (AIMD) confirm its thermal stability during sodium storage, underscoring P5C6's potential as a promising SIB anode material.
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•Inventive heterostructure P5C6 mixes BP and graphene synergy perks capably.•Na intercalation into P5C6 yields a theoretical capacity of 590.5 mAh/g.•P5C6 presents fast sodium diffusion, with a 0.019 eV low energy barrier.•Insertion of Na into P5C6 can enhance electronic conductivity.•P5C6 serves as a superb anode for SIBs: excellent performance.
