Hydrogen Storage Ability Research Articles

High hydrogen storage ability of a decorated g-C3N4 monolayer decorated with both Mg and Li: A density functional theory (DFT) study

In this work, the hydrogen storage properties of a g-C3N4 monolayer decorated with both Mg and Li were thoroughly investigated by performing density functional theory (DFT) calculations. Along these lines, the projected densities of states (PDOS) and the Bader Charge analysis showed that both Mg and Li atoms can transfer their electronic charges to the g-C3N4 monolayer. Interestingly, the latter is transformed from a semiconductor material to a metallic conductor configuration, while a local electric field is formed around it. On top of that, the formed local electric field polarized hydrogen molecules and as a result, led to an enhanced hydrogen adsorption ability. Mg atoms have more outmost electrons, and more charges can be transferred to the monolayer, which leads to the creation of a stronger local electric field to adsorb an elevated number of hydrogen molecules than Li atoms. On the other hand, Li atoms are lighter, more active and easier to lose outmost electrons than Mg atoms. By considering these advantages, a g-C3N4 monolayer decorated with one unit of both Mg and Li was investigated, which has the ability to adsorb 10 hydrogen molecules, leading thus to a high hydrogen storage capacity of 10.01 wt %. Our work paves the way for the development of novel material configurations for improved hydrogen storage applications.

Zn(II)-isatin-3-thiosemicarbazone complexes with phosphines or diamines for hydrogen storage and anticancer studies

• Novel six zinc(II) mixed ligand complexes of isatin-3-thiosemicarbazone (HITC) and phosphines or diamines were successfully prepared. • The complex [Zn 2 (ITC) 2 µ-(dppm) 2 ]Cl show the ability to store 2.33 wt% of hydrogen. • The complexes showed that the value of cell viability was only 3% for [Zn(ITC)(Bipy)]Cl at a concentration of 400 μM, while it did not exceed 10% for the rest of the tested complexes. Novel six zinc(II) mixed ligand complexes of isatin-3-thiosemicarbazone (HITC) and phosphines or diamines were successfully prepared. These coordination materials were all diagnosed using C.H.N, molar conductivity, FTIR and 1 H, 13 C, 31 P NMR measurements. The analyzes indicated that zinc(II) complexes possess a tetrahedral shape and the ligand (ITC) showed only one coordination mode, negatively charged ITC bounded as a bidentate chelate through the exocyclic nitrogen and the negatively charged sulfur atoms. Four complexes were tested as anti-ovarian cancer, and the results demonstrated that these coordination compounds have a high ability to prevent the growth of tumor cells. The value of cell viability was only 3% for [Zn(ITC)(Bipy)]Cl at a concentration of 400 μM, while it did not exceed 10% for the rest of the tested complexes. Moreover, the hydrogen storage ability of some complexes were examined under different pressures (0–90 bar) at 77 K. The results demonstrate that the complex [Zn 2 (ITC) 2 µ-(dppm) 2 ]Cl 2 is a potential material for storing hydrogen in physical absorption.

Applying the wavelet neural network to estimate hydrogen dissolution in underground sodium chloride solutions

It is possible to store large-scale hydrogen in underground sodium chloride solutions. Accurate knowledge of hydrogen-brine phase equilibrium is necessary for fully benefiting from this process and successful hydrogen storage in the underground brine. Hence, it is essential to develop a reliable method for accurately monitoring the hydrogen dissolution in brine. This study utilizes the wavelet neural network (WNN) to relate the hydrogen storage ability of brine to its main influential variables, i.e., pressure, temperature, and NaCl molality. Akaike information criterion demonstrates that a single hidden layer WNN with thirteen neurons is the most efficient topology for the given purpose. This model accurately monitors hydrogen-brine phase equilibrium with the mean squared error of 2.65 × 10−5 and regression coefficient of 0.99915. Relevancy analysis shows that temperature and pressure increase, and NaCl concertation decreases brine hydrogen storage capacity. The leverage method distinguishes 257 valid measurements and six outliers in the gathered databank.

Hydrogen Storage Mechanism in Sodium-Based Graphene Nanoflakes: A Density Functional Theory Study

Carbon materials, such as graphene nanoflakes, carbon nanotubes, and fullerene, can be widely used to store hydrogen, and doping these materials with lithium (Li) generally increases their H2-storage densities. Unfortunately, Li is expensive; therefore, alternative metals are required to realize a hydrogen-based society. Sodium (Na) is an inexpensive element with chemical properties that are similar to those of lithium. In this study, we used density functional theory to systematically investigate how hydrogen molecules interact with Na-doped graphene nanoflakes. A graphene nanoflake (GR) was modeled by a large polycyclic aromatic hydrocarbon composed of 37 benzene rings, with GR-Na-(H2)n and GR-Na+-(H2)n (n = 0–12) clusters used as hydrogen storage systems. Data obtained for the Na system were compared with those of the Li system. The single-H2 GR-Li and GR-Na systems (n = 1) exhibited binding energies (per H2 molecule) of 3.83 and 2.72 kcal/mol, respectively, revealing that the Li system has a high hydrogen-storage ability. This relationship is reversed from n = 4 onwards; the Na systems exhibited larger or similar binding energies for n = 4–12 than the Li-systems. The present study strongly suggests that Na can be used as an alternative metal to Li in H2-storage applications. The H2-storage mechanism in the Na system is also discussed based on the calculated results.

Composition design, synthesis and hydrogen storage ability of multi-principal-component alloy TiVZrNbTa

A thermodynamic model was proposed to assess the feasibility of the synthesis of single-phase multi-principal-component alloy. Based on this model, single-phase TiVZrNbTa equiatomic alloys with body centered cubic (BCC) structure were obtained by arc melting (AM), electron beam melting with pendant drop melt extraction (EBM-PDME) and mechanical alloying (MA). The alloys were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, thermal analysis and mechanical testing. The hydrogenation behavior of the synthesized materials was studied by a volumetric method. It was found that for AM and EBM-PDME alloys a complete BCC-to-FCC structure transformation occurs upon hydrogenation, and hydrogen concentration in the hydrides formed reaches 1.5 H/M (1.6 wt%). MA alloy undergoes partial amorphization with maximum hydrogen absorption capacity of 0.9 wt%.

Modification of graphenylene nanostructure with transition metals (Fe, Sc and Ti) to promote hydrogen storage ability: A DFT-D3 study

Hydrogen, as a clean alternative to fossil fuels, has received much attention in recent years. But its utilizing requires to overcome storage problems. Here, we investigated the hydrogen adsorption behavior of graphenylene (GPY), a 2D carbon nanostructure, and Sc, Fe and Ti transition metal (TM) decorated GPY by spin-polarized DFT calculations. For TM-decoration of GPY, seven different sites and various distances from carbon sheet were investigated, carefully. Structural and electronic properties of the structures, adsorption energies, band gap values, and the most stable configurations were considered and discussed. Results showed that 6-membered ring (H2 site) is the best site for Sc, Fe, and Ti-decoration and corresponding Eads was −3.95, −2.66, and −3.65 eV, respectively. Also, pristine GPY and Sc and Ti-decorated GPY have not magnetic character, unlike Fe-GPY. As well, entrance of Sc, Fe and Ti atoms in H2 site of the GPY structure causes its band gap increases from 0.033 eV to of 0.491, 0.080, and 0.372 eV, respectively. Eads of the H2 molecule onto pristine GPY is low (−0.160 eV), and must be improved for practical hydrogen storage applications. Sc, Fe, and Ti-decoration improves it about 2.23, 5.69 and 3.63 times. Because of this improvement, we could store up to 20H2 molecules on TM-decorated GPY systems. These results indicate that TM-decorated GPY can be a suitable option for H2 storage applications in the future.

Divulging the electrochemical hydrogen storage of ternary BNP-doped carbon derived from biomass scaled to a pouch cell supercapacitor

Activated carbon materials have been studied extensively as electrode materials for supercapacitors (SCs), but their poor capacitance and energy density have hampered their growth. We present a one-step synthesis of a ternary boron-nitrogen-phosphorous-doped carbon (BNPC) from biomass hemp fibre to determine its electrochemical hydrogen storage ability using SC applications. FESEM micrographs reveal mixed morphologies like square, diamond and cylindrical-shaped nanosheets, confirming the hetero-atom doping into the carbon skeleton. The optimized BNPC electrode delivers a half-cell specific capacitance and hydrogen-storage capacity of 520 Fg-1 (1 Ag-1) and 360 mAhg−1 (10 mVs−1), respectively. To demonstrate the practicability of the as-prepared BNPC electrode, a symmetric pouch-cell supercapacitor device was assembled which exhibits a full-cell specific capacitance of 262.56 Fg-1 at 1 Ag-1 and a specific energy of ~118 Wh kg−1 at a specific power of ~5759 Wkg-1 with an operating potential window of 1.8 V and 99.7% capacitance retention over 10,000 cycles. This excellent electrochemical performance can be ascribed to the synergetic properties of fast-electrolyte-ion diffusion due to the doping of heteroatoms into the carbon matrix, high conductivity and high specific surface area and effective microporosity of BNPC (1555.5 m2g-1). Also, the chemical stability of the BNPC materials, was investigated with density functional theory (DFT)-single point calculations, where the least molecular orbital energy gap was obtained by the BNPC, which confirms its structural stability. Thus, the prepared ternary BNP-doped carbon derived from biomass has provided a new direction to enhance the electrochemical energy storage potential.

Ab initio study of lithium decoration of popgraphene and hydrogen storage capacity of the hybrid nanostructure

The successful realization of extended ‘5-5-8’ line defects in graphene in a controlled way has suggested the possible formation of a new 2D carbon allotrope consisting in pentagonal-octagonal-pentagonal carbon rings. The mechanical and thermal stability of this nanostructure, called popgraphene, has recently been confirmed on the basis of first-principles calculations. Moreover, it has been proposed as a promising anode material for use in Li-ion batteries with fast charge/discharge rates. In the present paper we perform density functional theory calculations to investigate the hydrogen storage ability of popgraphene. Our calculations show that popgraphene can be decorated in a very stable way by placing Li atoms on the pentagonal carbon rings of both sides of the sheet, leaving free the octagonal carbon rings. In that condition, the Li-decorated popgraphene sheet can bind up to four H2 molecules per unit cell, with an average adsorption energy in a range between physisorption and atomic chemisorption, which would allow for reversible hydrogen storage at moderate temperatures and pressures. Moreover, the gravimetric density of the Li-decorated popgraphene is 4.24 wt%, which is almost equal to the threshold specified by the U.S. Department of Energy for novel hydrogen-storage materials. All these results show that Li-decorated popgraphene nanostructures could be good materials for hydrogen storage.

Effects of gaseous environments on physicochemical properties of thermally exfoliated graphene oxides for hydrogen storage: a comparative study

The present study compared the effect of different gaseous environments on physicochemical properties and subsequent hydrogen storage ability of thermally exfoliated graphene oxide (EGO). The reducing, inert or oxidizing environments were generated using hydrogen, argon or air as the carrier gas, respectively. The structure of thermally exfoliated graphene oxide depended on the type of gaseous environment. The EGO prepared in presence of Air showed the fluffiest layered structure having highest surface area. The surface area order was EGO(Air) (268 m2/g) > EGO(H2) (248 m2/g) > EGO(Ar) (155 m2/g). The average pore sizes of EGO(Air) and EGO(H2) were 2.9 and 2.8 nm, with pore volumes of 1.2 and 1.6 cm3/g, respectively. The average pore size for EGO(Ar) was highest at 4.1 nm, associated with presence of larger void space and lowest total pore volume of 1.0 cm3/g. Thus, presence of oxidative or reducing atmosphere seemed to be more conducive to exfoliation of layers by gradual removal of functional groups. The inert atmosphere of argon caused severe thermal separation of layers and functional groups, adversely affecting the layered structure as observed. The EGO(Air) also showed highest O/C ratio suggesting presence of significant amount of oxygen–containing functional groups on the surface. The hydrogen uptake order at 77 K and 30 bar was: EGO (Air) 3.34 wt.% > EGO (H2) 3.12 wt.% > EGO (Ar) 2.2 wt.%. The highest uptake of EGO(Air) might have resulted from highest surface area, highest O/C ratio and presence of considerable pore volume.

Li‐decorated Al2C monolayer as a potential template for hydrogen storage: A first‐principles perspective

AbstractThe potential application of Li‐decorated Al2C template for hydrogen storage is researched by using periodic DFT computations. Based on the obtained results, pristine Al2C monolayer gets adsorb up to four H2 molecules that give hydrogen uptake capacities of 5.7 wt% with an average binding energy of 0.14 eV/H2. It is predicted that the decoration of Al2C monolayer with Li atoms significantly improves the hydrogen storage ability of the desired monolayer compared to that of pristine Al2C monolayer. This can be attributed to the polarization of H2 molecules induced by the charge transfer from Li atoms to Al2C monolayer. Decoration of Al2C monolayer with two Li atoms gives a promising medium that gets adsorb maximum of ten H2 molecules with hydrogen uptake capacities of 12.1 wt% and adsorption energies within the range of 0.24‐0.47 eV. It is inferred that hydrogen desorption from 2Li/Al2C(10H2) system can occur at TD = 313 K and P = 1 atm which is near to the ambient conditions. This is an important result indicating potential usage of 2Li/Al2C medium for hydrogen storage purposes.

First-principles study of superior hydrogen storage performance of Li-decorated Be2N6 monolayer

The potential application of pristine Be2N6 monolayer and Li-decorated Be2N6 monolayer for hydrogen storage is researched by using periodic DFT calculations. Based on the obtained results, the Be2N6 monolayer gets adsorb up to seven H2 molecules with an average binding energy of 0.099 eV/H2 which is close to the threshold energy of 0.1 eV required for practical applications. Decoration of the Be2N6 monolayer with lithium atom significantly improves the hydrogen storage ability of the desired monolayer compared to that of the pristine Be2N6 monolayer. This can be attributed to the polarization of H2 molecules induced by the charge transfer from Li atoms to the Be2N6 monolayer. Decoration of Be2N6 monolayer with two lithium atoms gives a promising medium that can hold up to eight H2 molecules with average adsorption energy of 0.198 eV/H2 and hydrogen uptake capacities of 12.12 wt%. The obtained hydrogen uptake capacity of 2Li/Be2N6 monolayer is much higher than the target set by the U.S. Department of Energy (5.5 wt% by 2020). Based on the van't Hoff equation, it is inferred that hydrogen desorption can occur at TD = 254 K for 2Li/Be2N6 (8H2) system which is close to ambient conditions. This is a remarkable result indicating important practical applications of 2Li/Be2N6 medium for hydrogen storage purposes.

A WS2 Case Theoretical Study: Hydrogen Storage Performance Improved by Phase Altering

Hydrogen is a clean energy with high efficiency, while the storage and transport problems still prevent its extensive use. Because of the large specific surface area and unique electronic structure, two-dimensional materials have great potential in hydrogen storage. Particularly, monolayer 2H-WS2 has been proven to be suitable for hydrogen storage. But there are few studies concerning the other two phases of WS2 (1T, 1T′) in hydrogen storage. Here, we carried out first-principle calculations to investigate the hydrogen adsorption behaviors of all the three phases of WS2. Multiple hydrogen adsorption studies also evaluate the hydrogen storage abilities of these materials. Comprehensive analysis results show that the 1T′-WS2 has better hydrogen storage performance than the 2H-WS2, which means phase engineering could be an effective way to improve hydrogen storage performance. This paper provides a reference for the further study of hydrogen storage in two-dimensional materials.

Carbon Nanotubes-Based Nanomaterials and Their Agricultural and Biotechnological Applications.

Carbon nanotubes (CNTs) are considered a promising nanomaterial for diverse applications owing to their attractive physicochemical properties such as high surface area, superior mechanical and thermal strength, electrochemical activity, and so on. Different techniques like arc discharge, laser vaporization, chemical vapor deposition (CVD), and vapor phase growth are explored for the synthesis of CNTs. Each technique has advantages and disadvantages. The physicochemical properties of the synthesized CNTs are profoundly affected by the techniques used in the synthesis process. Here, we briefly described the standard methods applied in the synthesis of CNTs and their use in the agricultural and biotechnological fields. Notably, better seed germination or plant growth was noted in the presence of CNTs than the control. However, the exact mechanism of action is still unclear. Significant improvements in the electrochemical performances have been observed in CNTs-doped electrodes than those of pure. CNTs or their derivatives are also utilized in wastewater treatment. The high surface area and the presence of different functional groups in the functionalized CNTs facilitate the better adsorption of toxic metal ions or other chemical moieties. CNTs or their derivatives can be applied for the storage of hydrogen as an energy source. It has been observed that the temperature widely influences the hydrogen storage ability of CNTs. This review paper highlighted some recent development on electrochemical platforms over single-walled CNTs (SWCNTs), multi-walled CNTs (MWCNTs), and nanocomposites as a promising biomaterial in the field of agriculture and biotechnology. It is possible to tune the properties of carbon-based nanomaterials by functionalization of their structure to use as an engineering toolkit for different applications, including agricultural and biotechnological fields.

Microwave synthesis of Nano/Micronized zeolites from natural source: Evaluation of energy storage capacities

This is a comparative study to investigate the hydrogen Storage ability of three zeolites; Zeolite-A, Faujasite-NaX and Analcime, prepared via microwave technique from refined kaolin. The paper addresses the effects of crystallite size, Si/Al, pore diameter and specific surface area on the hydrogen uptake capacity. X-Ray Fluorescence is used for rock chemical analysis, X-ray Diffraction for zeolite mineralogy, Scanning Electron Microscopy and Transmission Electron Microscopy for microstructure. Whereas, Electron Dispersion Analysis monitors chemical microanalysis. Storing hydrogen is processed via Pressure, Composition and Temperature, using AMC PCI-HP 1200 equipment, meanwhile, BEL Sorb Max device (BEL JAPAN. INC) is used for specific surface area. Result indicates that, decreasing crystallite size has positive effects on both total pore volume and specific surface area, with a net result of higher hydrogen gravimetric capacities for all structures. At 77K and 22 bar, nano- Faujasite presents the highest hydrogen uptake of 2.25 wt%, whereas, nano Analcime hosts the least amounts of hydrogen of 0.74 wt%. Despite of the effect of zeolite particle size reduction on the surface area enlargement and high adsorption capacity, the limiting factor in hydrogen uptake into zeolite porous vicinities is the diameter of the pores and the blocking effects of their channels.

Effect of adding TiO2, SiO2 and graphene on of electrochemical hydrogen storage performance and coulombic efficiency of CoAl2O4 spinel

One of the famous blue pigments is cobalt aluminate which has a normal spinel that in this work has been synthesized with thermal decomposition technique via the help of olive leaf extract as a precipitation agent. Furthermore, CoAl2O4/SiO2, CoAl2O4/TiO2 and CoAl2O4/graphene nanocomposites were prepared besides the pure one. To investigate the structure and composition of products, X-ray diffraction (XRD) pattern and Fourier transform infrared (FT-IR) analysis were served. Also, the morphologies of products were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the effect of different nucleation and growth conditions of the products were investigated. The hydrogen storage ability of the pure CoAl2O4 nanostructures was investigated and to increase the hydrogen storage capacity, different CoAl2O4 nanocomposites were prepared and studied. The maximum discharge capacity and Coulombic efficiencies are 2800 mAh/g and 62% that related toCoAl2O4/TiO2 composition and CoAl2O4, respectively.

Novel Hg(II) and Pd(II) benzotriazole (Hbta) complexes: Synthesis, characterization, X-ray crystal structure of [Pd(PPh3)(μ-bta)Cl]2. DMSO and thermodynamic study of their H2 storage

Benzotriazole (Hbta) complexes with Hg(II) and Pd(II) of the types: [Hg(bta)2] (1), [Hg(bta)2(diphos)]; diphos = dppe (2), dppp (3) or dppb (4), [Hg(bta)2(PPh3)2] (5), [Pd(Hbta)2Cl2] (6), [Pd(bta)Cl]2 (7) and [PdCl(bta)(PPh3)]2.DMSO (8) were prepared and characterized by elemental analyses, conductivity measurements, infrared, 1H- and 31P-{1H} NMR spectra.[Pd(PPh3)(μ-bta)Cl]2. DMSO (8) was structurally characterized by single-crystal X-ray diffraction. Structural information exposed that benzotriazole acts as a bidentate bridging ligand bonded through the deprotonated nitrogen and the neutral nitrogen atoms. The hydrogen storage ability of complexes (1–4) was studied after detecting their BET surface area. The results show that complex (1) is able to store 3.35 wt% physically at 77 K under 120 bar.

Numerical investigation of hydrogen absorption in a metal hydride reactor with embedded embossed plate heat exchanger

In this paper, a Metal Hydride (MH) reactor integrated with an Embossed Plate Heat Exchanger (EPHX) was studied for the first time for its hydrogen absorption rate and thermal performance. A detailed numerical analysis of the various flow-field designs in the EPHX such as parallel-type, pin-type, and serpentine types (vertical and horizontal) was performed. The serpentine flow-field EPHX presented better heat transfer and faster hydrogen storage ability. Also, it showed more uniform temperature distribution in the bed compared with parallel and pin-type flow-fields. Next, the vertical-serpentine flow-field EPHX was compared with the most commonly used Helical Coil Heat Exchanger (HCHX) and the outcomes were discussed. Although, EPHX showed slightly lower overall heat removal from the reactor, it presented similar hydrogen absorption rate and remarkable uniformity in temperature distribution in the reactor.

Tuning the hydrogen storage properties of MOF-650: A combined DFT and GCMC simulations study

Combined density functional theory and grand canonical monte Carlo (GCMC) calculations were performed to study the electronic structures and hydrogen adsorption properties of the Zn-based metal-organic framework MOF-650. The benzene azulenedicarboxylate linkers of MOF-650 were substituted by B atoms, N atoms, and boronic acid B(OH)2 linkers, and the Zn atoms were substituted by Mg and Ca atoms. The calculated electronic densities of states (DOSs) of MOF-650 showed that introduction of B atoms reduces the band gap but damages the structure of MOF-650. Introduction of single N bonds cannot provide active electrons to attract H2 molecules. Thus, substitutions of B and N into MOF-650 are not suggested. B(OH)2 substitute in MOF-650 decreased its band gap, slightly improved its hydrogen storage ability and made H2 molecules more intensively distributed besides organic linkers. GCMC calculations were carried out by estimating the H2 storage amount of the pure and modified MOFs at 77 and 298 K and from 1 bar to 20 bar. B(OH)2 linker and Mg/Ca co-doped MOF-650 showed increased H2 adsorption by approximately 20 wt%. The adsorption of H2 around different bonds showed the order N–C < C = C < B–C < C–O < B–O.

Li4Zn3B4O11/Li2B2O4 Nanocomposites as a Potential Electrode Material for Electrochemical Hydrogen Storage; Insight of Fabrication and Morphology Controlling

Li4Zn3B4O11/Li2B2O4 (LZBO/LBO) nanocomposites with controlled morphologies were fabricated through pechini sol-gel method. The effect of EDTA against various carboxylic acids (as chelating agents) compered in order to investigation shape, size and representative characteristics. To further inspect, the effect gelling agents examined on the synthesis process. The electrochemical process of hydrogen storage in the Li4Zn3B4O11/Li2B2O4 nanocomposites electrode employing the electrodecomposition of KOH electrolyte has been considered by means of galvanostatic charge-discharge method. It seems that multidisciplinary mechanisms for storage function of obtained nanocomposites involve layered structures, distinct morphology, and physical adsorption lead to fantastic hydrogen storage ability. The hydrogen storage capability for two type morphologies of sphere/rod and nanoparticles assess 222/5 and 402/5 mA h/g, respectively. Based on the acquired consequences, Li4Zn3B4O11/Li2B2O4 nanocomposites can be hopeful components to upgrade the hydrogen storage operation through electrochemical procedure.

Transition‐Metal‐Based Multidecker Complexes as Hydrogen Storage Materials: A Theoretical Study

AbstractHydrogen economy has gained pace globally due to the depletion of fossil fuels at an alarming rate. A good number of multidecker transition metal complexes have been studied for their hydrogen storage ability. However, the problem of finding an ideal multidecker system for hydrogen storage applications still remains a challenge. Herein, we report a comparative study on multidecker complexes of VTi(C6H6)3, Sc2(C6H6)3, and Sc2(C5H5)2(C6H6) using density functional theory at PBEPBE functional and 6–31G (d,p) basis set level of theory. The three complexes show hydrogen adsorption capacity in a range of 2.94 to 5.28 wt%, with an average binding energy of 0.65 to 0.92 eV/H2. Trends in adsorption energies, Gibbs free energy changes and energy gaps indicate the adsorption of H2 molecules on these multidecker complexes is thermodynamically and kinetically favorable.