Hexagonal boron nitride (h-BN) nanoparticles decorated multi-walled carbon nanotubes (MWCNT) for hydrogen storage

Hydrogen is considered as the most promising clean energy carrier because of its abundance, environmental friendliness and high conversion efficiency. However, developing safe, compact, light weight and cost-effective hydrogen storage materials is one of the most technically challenging barriers to the widespread use of hydrogen as fuel. The present work reports the hydrogen storage performance of multi-walled carbon nanotubes (MWCNT)/hexagonal boron nitride (h-BN) nanocomposites (MWCNT/h-BN), where ultrasonication method is adopted for the synthesis of the MWCNT/h-BN nanocomposites. Hydrogenation process was carried out using Seiverts-like hydrogenation setup. Characterization techniques such as X-ray Diffraction (XRD), Micro-Raman Spectroscopy, Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX), Nitrogen adsorption–desorption isothermal studies (BET), CHN-elemental analysis and Thermogravimetric Analysis (TGA) were used to analyze the samples at various stages of the experiment. A maximum of 2.3 wt% hydrogen storage is achieved in the case of acid treated MWCNTs (A-MWCNT) with 5 wt% of h-BN nanoparticles compared to pure MWCNTs that could store 0.15 wt% only. Moreover the calculated binding energy (0.42 eV) of stored hydrogen of A-MWCNT with 5 wt% of h-BN nanocomposite lies in the recommended range of binding energy (0.2–0.6 eV) for fuel cell applications. The TG study shows that 100% desorption is achieved at the temperature range of 120–410 °C and confirms that the prepared hydrogen storage medium will serve effectively in the realm of hydrogen fuel economy in near future.     

Synthesis of boron and nitrogen co-doped carbon nanotubes and their application in hydrogen storage

Boron and nitrogen codoped carbon nanotubes (B,N-CNTs) were synthesized by floating catalyst chemical vapor deposition (FCCVD) using ethanol, ferrocene, boric acid and imidazole as carbon source, catalyst, boron and nitrogen precursors, respectively. The samples were analyzed using transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and X-ray photoemission spectroscopy. 1.5 at% B and 1.34 at% N could be doped in the resultant structure, which has higher length (few μm) with higher thermal stability (621 °C). At pressure 16 bar, hydrogen adsorption for B,N-CNTs was found to be 1.96 and 0.35 wt% at 77 K and 303 K, respectively. Hydrogen storage as function of time was also reported for both the cases. The adsorption process follow pseudo second order kinetics. The present study reveals that the codoping of CNTs aid in tuning properties of CNTs for hydrogen storage application.     

Characterization and the hydrogen storage capacity of titania-coated electrospun boron nitride nanofibers

In the present work, titania-coated (TiO₂) boron nitride nanofibers were produced by the electrospinning method, and the effect of heat treatment on the nanofibers was studied. Electrospinning method is often adopted for the synthesis of one-dimensional nanofibers due to high productivity, simplicity, and cost-effectiveness. In this study, boric oxide was deposited on co-electrospun polyacrylonitrile and TiO₂. TiO₂-coated boron nitride nanofibers, with a diameter of 100 nm, were obtained after heat treatment and nitridation. The effects of heat treatment on the morphology, surface area and hydrogen storage capacity were studied extensively. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) showed long, bead-free nanofibers and the presence of TiO₂ nanoparticles on the nanofibers. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy depicted hexagonal structures of boron nitride. The hydrogen uptake capacities of the nanofibers were investigated by pressure composition isotherm (PCI) in the pressure range of 1–70 bar at room temperature.     

Synthesis and hydrogen storage properties of different types of boron nitride nanostructures

The present work reports the synthesis and hydrogen storage properties of different types of boron nitride (BN) nanostructures prepared by an in situ silica-assisted catalytic chemical vapor deposition technique. The BN nanostructures have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Brunauer, Emmett, and Teller (BET), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy studies. The hydrogen storage properties of BN nanostructures have been investigated using a high-pressure Seiverts' apparatus in the pressure range of 1–100 bar and at 298 K. The dependence of hydrogen storage capacity on the morphology of BN nanostructures is discussed in detail.     

Effect of boron substitution on hydrogen storage capacity of Li and Ti decorated naphthalene

Interaction of molecular hydrogen with Li and Ti doped boron substituted naphthalene viz. C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ has been studied using density functional theory (DFT) method. The C₆B₄H₈Li₂ complex can interact with maximum of four hydrogen molecules, whereas three H₂ molecules are adsorbed on C₁₀H₈Li₂ complex. The C₆B₄H₈Ti₂ complex can interact with maximum of eight hydrogen molecules. The gravimetric hydrogen uptake capacity of C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ complex is found to be 6.85 and 5.55 wt % respectively, which is higher than that of unsubstituted C₁₀H₈Ti₂ and C₁₀H₈Li₂ complexes. The boron substitution has significantly affected the hydrogen adsorption energies. The H₂ adsorption energy and Gibb's free energy corrected H₂ adsorption energy are found to be more prominent after boron substitution. The C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ complexes are more stable than the respective unsubstituted C₁₀H₈Ti₂ and C₁₀H₈Li₂ complexes due to their higher binding energies. According to the atom-centered density matrix propagation (ADMP) molecular dynamics simulations C₆B₄H₈Li₂ complex retain not a single adsorbed hydrogen molecule during the simulation at room temperature, whereas five hydrogen molecules at 300 K and eight at 100 K are remain absorbed on C₆B₄H₈Ti₂ complex. The C₆B₄H₈Ti₂ complex is found to be more promising material for hydrogen storage than C₁₀B₄H₈Li₂.     

A theoretical first principles computational investigation into the potential of aluminum-doped boron nitride nanotubes for hydrogen storage

Hydrogen storage remains a largely unsolved problem facing the green energy revolution. One approach is physisorption on very high surface area materials incorporating metal atoms. Boron nitride nanotubes (BNNTs) are a promising material for this application as their behaviour is largely independent of the nanoscopic physical features providing a greater degree of tolerance in their synthesis. Aluminum doping has been shown to be a promising approach for carbon nanotubes but has been underexplored for BNNTs. Using first principles density functional theory, the energetics, electronics and structural impacts of aluminum adsorption to both zigzag and armchair polymorphs of BNNTs was investigated along with their potential capacity to adsorb hydrogen. The fine atomic structural and electronic details of these interactions is discussed. We predicted that in an ideal situation, highly aluminum-doped armchair and zigzag BNNTs could adsorb up to 9.4 and 8.6 wt percent hydrogen, well above the United States Department of Energy targets marking these as promising materials worthy of further study.     

Investigation of single-walled carbon nanotubes-titanium metal composite as a possible hydrogen storage medium

The present experimental work deals with the investigation of hydrogen uptake study of single-walled carbon nanotubes (SWCNTs-Ti)-titanium metal composite. The mixture containing SWCNTs and Ti powder is made into tablet by cold pressing. The composite has been prepared and hydrogenated by evaporating the tablet in hydrogen ambient on glass substrates using electron beam (EB) evaporation technique. Efficient hydrogen uptake of 4.74 wt.% is achieved with the composite and the adsorbed hydrogen posses the average hydrogen binding energy of 0.4 eV. The obtained hydrogen uptake is due to the cumulative adsorption of hydrogen by CNTs and Ti nanostructured materials. The physical properties are characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction study (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Raman analysis. Hydrogenation and dehydrogenation behavior of the composite are studied using CHN-elemental analysis and thermo gravimetric/thermal desorption spectroscopy (TG/TDS) studies, respectively. The stored hydrogen is found to be 100% reversible in the temperature range of 160–310 °C.     

Calcium hydrazinidoborane: Synthesis,characterization, and promises for hydrogen storage

Viewing calcium hydrazinidoborane Ca(N₂H₃BH₃)₂ (9.3 wt% H) as a potential hydrogen storage material, we long sought to synthesize it by solid-solid reaction of calcium hydride CaH₂ and hydrazine borane N₂H₄BH₃. However, it was elusive because of unsuitable experimental conditions. In situ synchrotron thermodiffraction helped us to identify the key role played by the temperature in the formation of the new phase. From 45 °C, new diffraction peaks appear, and the DSC analysis shows an exothermic signal. Thermal activation is thus required to make solid-state CaH₂ react with melted (liquid-state) N₂H₄BH₃. The XRD pattern can be indexed using a mixture of two phases: (i) unreacted CaH₂ as a minor phase (29 wt%) and (ii) the hitherto elusive Ca(N₂H₃BH₃)₂ (71 wt%). The as-formed Ca(N₂H₃BH₃)₂ crystallizes in a monoclinic Ic (No. 9) unit cell where the intermolecular interactions form chains (layers) along the a axis, resulting in intra-chain and inter-chain Ca⋅⋅⋅Ca distances as short as 4.39 and 7.04 Å respectively. Beyond 90 °C, Ca(N₂H₃BH₃)₂ decomposes, as evidenced by the diffraction peaks fading, an exothermic signal revealed by DSC, a weight loss (5.3 wt% at 200 °C) observed by TGA, and a gas release (H₂, and some N₂, NH₃, N₂H₄) monitored by MS. The as-formed thermolytic residue is amorphous and of complex polymeric composition. These results and the next challenges, are discussed herein.     

Magnesium hydrazinidoborane: Synthesis,characterization and features for solid-state hydrogen storage

After various attempts, we present a new alkaline-earth derivative of hydrazine borane (N₂H₄BH_3, HB), magnesium hydrazinidoborane (Mg(N₂H₃BH₃)₂, Mg(HB)₂, 10.5 wt % H), that was undoubtedly identified by FTIR and ¹¹B MAS NMR spectroscopy. Mg(HB)₂ was obtained by an alternative synthesis route, which is the reaction between HB and di-n-butylmagnesium in THF. The dehydrogenation properties of this compound were evaluated by two different approaches: an “open” system by thermogravimetric analysis and differential scanning calorimetry, and in a closed system, by heating the compound under isothermal conditions. Different results were obtained depending on the approach. Unlike other boron- and nitrogen-based compounds, it is likely that when Mg(HB)₂ is heated in a closed system, the dehydrogenation is limited and it occurs mainly due to the homopolar interaction between the protic hydrogen atoms of the molecule. Also, Mg(HB)₂ presents a contrasting thermal behavior in comparison with previous HB derivatives. In addition, a characterization by X-ray photoelectron spectroscopy was performed, and we detected instability of Mg(HB)₂ when it was irradiated with the X-ray beam. All of these results are presented and discussed in the context of materials for hydrogen storage in the solid-state.     

Facile synthesis and hydrogen storage application of nitrogen-doped carbon nanotubes with bamboo-like structure

This paper reports a facile method for the preparation of nitrogen-doped carbon nanotubes (N-doped CNTs) that shows enhanced hydrogen storage capacity. The synthesis method involves simple pyrolysis of melamine using FeCl₃ as catalyst in tube furnace. The materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, elemental analysis, Raman spectroscopy, and nitrogen adsorption–desorption analysis. The results indicated that the prepared N-doped CNTs have a bamboo-like structure with thin compartment layers. The nitrogen doping concentration, specific surface area, and total pore volume of the N-doped CNTs were determined to be 1.5 at%, 135 m²/g, and 0.38 cm³/g, respectively. The hydrogen adsorption measurements at 77 K showed that the N-doped CNTs exhibits gravimetric hydrogen uptake of 0.21 wt% at 1 bar and 1.21 wt% at 7 bar. At room temperature, hydrogen uptake as high as 0.17 wt% at 298 K and 19 bar is achieved, which is among the highest data reported for the N-doped carbon materials under the same condition.     

Hybrid laser ablation and chemical reduction to synthesize Ni/Pd nanoparticles decorated multi-wall carbon nanotubes for effective enhancement of hydrogen storage

Simultaneous laser ablation and chemical reduction processes are introduced here to decorate the multi-wall carbon nanotubes with metal nanoparticles (palladium and nickel) in order to enhance the hydrogen storage capacity. This lucidly elevates the abundance of metal nanoparticles, as well as creating more nano cavities in the carbon nanotubes leading to an effective surface enlargement. Transmission electron microscopy, X-Ray diffraction and microprobe as well as the thermal gravimetric analyses support the findings how to alter the size, shape, structure, elemental analysis and the population of nanoparticles dispersed around the carbon nanotubes. The pore size and surface morphology of the nanotubes are inspected based on Brunauer–Emmett–Teller and Barret–Joyner–Halenda analyses. Furthermore, the volumetric method is employed to investigate the hydrogen trapping within the carbon nanotubes of interest. The results attest that more metal nanoparticles are populated around the carbon nanotubes by making use of this hybrid method. The hydrogen content is measured to be 8.6% (2.5%) in nanoparticles decorated multi-wall carbon nanotubes having palladium (nickel) 67% (25.3%) by weight.     

Preparation and characterization of mica glass-ceramics as hydrogen storage materials

This work is an attempt to study storing hydrogen in safe, reliable, compact, and cost-effective glass-ceramics materials for the first time. The effect of replacing K⁺ by Na⁺ or Li⁺ in the fluorophlogopite formula KMg₃AlSi₃O₁₀F₂ was studied using DTA, XRD and SEM. Also the effect of the crystallized phases within glass-ceramics on the surface area and capacity of storing hydrogen under different pressures were studied. Replacement of K⁺ by Na⁺ or Li⁺ leads to increase the temperature of crystallization in the same order. XRD revealed crystallization of spodumene (LiAlSi₂O₆) and forsterite (Mg₂SiO₄) in GLi and Na-fluorophlogopite (NaMg₃AlSi₃O₁₀F₂) and Na-mica (NaAl₃Si₃O₁₁) in GNa while Lucite (KAlSi₂O₆) and forsterite in GK. Surface area measurements for optimum samples showed low values in the range 0.48–0.58 m²/g; also total pore volumes have low values 9.4 × 10^?4–6.99 × 10^?3 cm³/g. The hydrogen adsorption content reached 1.25, 2.5, 1.34 sand 1.9 wt% for GLi, GNa, GK and GK samples heated for 2 h at 770,1100, 1000 and 1100 °C, respectively. The results obtained that, Na-bearing samples are the proper for hydrogen storage wherein sodium mica and phlogopite with characteristic sheet structure were crystallized.     

Synthesis and characterization of mixed sodium and lithium fullerides for hydrogen storage

We herein report on the synthesis of mixed alkali cluster intercalated fullerides Na_xLi_y?xC₆₀ (y = 12; x = 1–6) by a two-steps mechanochemical reaction of fullerene with sodium and lithium. These compounds crystallize in the cubic lattice of C₆₀ displaying a contracted lattice parameter with respect to the Na₆C₆₀ parent structure. The analysis of the hydrogen sorption behaviour shows a slight decrease in the dehydrogenation enthalpy for y = 12 with respect to the sodium free member. Raman spectroscopy highlighted a partial electron transfer from alkali metals to C₆₀, suggesting the presence of charged sodium/lithium clusters. Finally, we applied muon spectroscopy to understand the different hydrogenation mechanisms in Na_xLi_6?xC₆₀ and Na_xLi_12?xC₆₀ and explain their different performance.     

Synthesis of cobalt hexacyanoferrate nanoparticles and its hydrogen storage properties

In the present paper, we report hydrogen storage properties of cobalt hexacyanoferrate nanoparticles as a function of temperature. Cobalt hexacyanoferrate nanoparticles were synthesized by facile chemical precipitation method. The resulted compound forms FCC structure analogous to Prussian blue and is found to be stable up to 550 K. Presence of characteristic absorption bands in the range of 2000–2300 cm^?1 in IR spectra corresponds to the CN stretching frequency of Fe(III)CNCo(II) sequence and this confirms the formation of Prussian blue analogues. Hydrogen adsorption studies were performed at variable temperatures. The effect of precursor concentration on hydrogen storage property has been investigated and interestingly, with increase in cobalt precursor concentration, hydrogen storage capacity is found to decrease. This correlates well with openness of the crystal structure. To the best of our knowledge, this is the first report on hydrogen storage properties of cobalt hexacyanoferrate.     

Synthesis and characterization of MWCNT impregnated with different loadings of SnO2 nanoparticles for hydrogen storage applications

Multi-walled carbon nanotubes (MWCNTs) loaded with different wt % of tin oxide (MWCNT: SnO₂) nanocomposites have been synthesized by impregnation method and their hydrogen uptake capacity is investigated. The hydrogen storage capacity of MWCNT: SnO₂ (3 wt %), MWCNT: SnO₂ (5 wt %), MWCNT: SnO₂ (7 wt %) and MWCNT: SnO₂ (9 wt %) composites is found to be 2.03, 1.95, 0.94 and 1.59 wt % respectively. The enhanced hydrogen storage capacity is due to SnOC bond formation and summative adsorption of hydrogen by MWCNT and SnO₂ nanoparticles. Moreover, physical/chemical properties of composites are examined by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction, thermogravimetric and Raman analyses. Hydrogen adsorption and desorption behavior of the composites are analyzed using Raman and thermogravimetric analyses. The stored hydrogen is desorbed in the temperature range of 183 ?C-536 °C.     

d-glucose and its analogue,d-glucosamine,as potential hydrogen storage materials: A quantum mechanical study

Cellulose and chitosan monomers have been studied as potential hydrogen storage materials with good gravimetric density and strong binding strength for the adsorption of hydrogen molecules. DFT calculations have been employed to examine the various available positions on the biomolecules for efficient hydrogen adsorption. FMO and NBO analysis revealed the strength of non-bonded interactions between adsorbent (cellulose, chitosan) and adsorbate (H₂ molecules). MEP analysis helped understand the charge separation upon H₂ adsorption at the available sites. The strong interaction is attributed to the presence of polar hydroxyl groups on the carbon backbone, which interacts with hydrogen through dipole-induced dipole interactions between the hydroxyl oxygen and H₂ molecules. Topological analysis for real space functions like electron density, ELF, LOL, NCI, and electrostatic potential was used to establish the nature of interactions. These findings can significantly impact the design of new hydrogen storage materials based on naturally available biopolymers with high hydrogen storage capacity at ambient temperature.     

Integrated design of hydrogen production and thermal energy storage functions of Al-Bi-Cu composite powders

In recent years, the hydrolysis of Al-based composite powders to produce hydrogen has become a hot topic in the field of hydrogen energy research. However, the hydrogen generation products of Al-based alloys have not been reasonably utilized. For this purpose, this study proposed a novel research idea to achieve the integrated design of hydrogen production and thermal energy storage functions of Al-based composite powders. Specifically, Al-Bi-Cu composite powders with stable hydrogen production were taken as research objects. The hydrogen was obtained by the reaction of Al-Bi-Cu alloy powders with H₂O for different reaction times, and then the hydrogen generation products were directly sintered at high temperature to obtain Al-Cu alloy based composite phase change thermal energy storage materials. The results indicated that at 50 °C, the hydrogen yield of Al-Bi-Cu alloy powders in 100min, 200min and 400min are 319.9 mL/g, 428.5 mL/g and 665.8 mL/g, respectively. Importantly, the Al-Cu alloy based composite phase change thermal energy storage materials prepared by the hydrogen generation products exhibited an adjustable phase change temperature (577.3 °C ∼ 598.2 °C), high thermal energy storage density (44.1J/g ∼ 153.5J/g), good thermal cycling stability and structural stability.     

Electroless deposition of Ni nanoparticles on carbon nanotubes with the aid of supercritical CO2 fluid and a synergistic hydrogen storage property of the composite

A hybrid synthesis protocol that combines electroless plating and the supercritical CO₂ (scCO₂) technique is developed for the first time to decorate multi-walled carbon nanotubes (CNTs) with Ni nanoparticles. The scCO₂ fluid, which is immiscible with aqueous plating solution, renders a heterogeneous Ni deposition reaction and suppresses the lateral growth of Ni, which leads to the formation of nanoparticles. A uniform dispersion of tightly anchored particles, a few nanometers in diameter, on CNTs can be achieved. Since the electroless deposition process can be easily manipulated, large-scale production should be realizable. The constructed CNT/Ni nano-composite exhibits a synergistic property in hydrogen storage performance, which is evaluated using a high-pressure microbalance. The deposited nanoparticles enhance the hydrogen spillover reaction on CNTs, tripling the hydrogen storage amount at room temperature as compared to pristine CNTs.     

Structural,hydrogen storage,and electrochemical performance of LaMgNi4 alloy and theoretical investigation of its hydrides

Structural, hydrogen storage, and electrochemical properties of LaMgNi₄ alloy were investigated in this study to determine whether it can be used as an active material of the negative electrode in nickel–metal hydride (Ni/MH) batteries. X-ray diffraction study showed that amorphization occurs at the first dehydrogenation cycle and was recovered crystallization after 873 K annealing.Maximum hydrogen storage capacity reached 1.4 wt% in the first hydrogenation under 373 K. The reannealed alloy showed improved reversible hydrogen storage capacity at ～0.9 wt% due to more LaNi₅ phase composition. Electrodes prepared from the investigated alloy showed maximum discharge capacities of ～340 mAh/g at 10 mA/g. The LaMgNi₄ alloy electrode exhibited satisfactory cycling stability remaining 47% of its initial capacity after 250 cycles. The negative cohesive energy indicated the exothermic process and stable compound structures of the LaMgNi₄ alloy and its hydrides via Density functional theory calculations.     

Functionality of graphene as a result of its heterogenic growth on SiC nanoparticles on the basis of reversible hydrogen storage

This article presents the results from research related to graphene functionality based on the production of spatial structures provided for the reversible storage of hydrogen. The functionality process was conducted during graphene synthesis onto a liquid metallic support, on a single level, using SiC nanoparticles. Within the scope of research it was proved that heterogenic growth of the domains of polycrystalline graphene onto the SiC nanoparticles is possible. These nanoparticles are in-built into the graphene structure constituting the pillars of the spatial structure. Material produced in such a way constitutes the foundation for creating a spatial 3D structure (through the rolling operation), called GraphRoll, for the reversible storage of hydrogen in order to conduct its sorption and de-sorption. So, independently of the theoretical configuration, deviations or a possible exception from the 2D configuration on the silicon carbide/graphene were discussed. These differences resulted from the difference between the crystallographic structures of the analyzed forms as well as the structure determined to decrease tensions within the structure.