Comparative Study of Hydrogen Adsorption on Carbon and BN Nanotubes

Utilizing Nanostructured Materials for Hydrogen Generation, Storage, and Diverse Applications

The rapid advancement of refined nanostructures and nanotechnologies offers significant potential to boost research activities in hydrogen storage. Recent innovations in hydrogen storage have centered on nanostructured materials, highlighting their effectiveness in molecular hydrogen storage, chemical storage, and as nanoconfined hydride supports. Emphasizing the importance of exploring ultra-high-surface-area nanoporous materials and metals, we advocate for their mechanical stability, rigidity, and high hydride loading capacities to enhance hydrogen storage efficiency. Despite the evident benefits of nanostructured materials in hydrogen storage, we also address the existing challenges and future research directions in this domain. Recent progress in creating intricate nanostructures has had a notable positive impact on the field of hydrogen storage, particularly in the realm of storing molecular hydrogen, where these nanostructured materials are primarily utilized.

Advances in boron nitride-based nanomaterials for environmental remediation and water splitting: a review

Boron nitride has gained wide-spread attention globally owing to its outstanding characteristics, such as a large surface area, high thermal resistivity, great mechanical strength, low density, and corrosion resistance. This review compiles state-of-the-art synthesis techniques, including mechanical exfoliation, chemical exfoliation, chemical vapour deposition (CVD), and green synthesis for the fabrication of hexagonal boron nitride and its composites, their structural and chemical properties, and their applications in hydrogen production and environmental remediation. Additionally, the adsorptive and photocatalytic properties of boron nitride-based nanocomposites for the removal of heavy metals, dyes, and pharmaceuticals from contaminated waters are discussed. Lastly, the scope of future research, including the facile synthesis and large-scale applicability of boron nitride-based nanomaterials for wastewater treatment, is presented. This review is expected to deliver preliminary knowledge of the present state and properties of boron nitride-based nanomaterials, encouraging the future study and development of these materials for their applications in various fields.

Recent Progress in Functional Nanomaterials towards the Storage, Separation, and Removal of Tritium

Tritium is a sustainable next-generation prime fuel for generating nuclear energy through fusion reactions to fulfill the increasing global energy demand. Owing to the scarcity-high demand tradeoff, tritium must be bred inside a fusion reactor to ensure sustainability and must therefore be separated from its isotopes (protium and deuterium) in pure form, stored safely, and supplied on demand. Existing multistage isotope separation technologies exhibit low separation efficiency and require intensive energy inputs and large capital investments. Furthermore, tritium-contaminated heavy water constitutes a major fraction of nuclear waste, and accidents like the one at Fukushima Daiichi leave behind thousands of tons of diluted tritiated water, whose removal is beneficial from an environmental point of view. In this review, the recent progress and main research trends in hydrogen isotope storage and separation by focusing on the use of metal hydride (e.g., intermetallic, and high-entropy alloys), porous (e.g., zeolites and metal organic frameworks (MOFs)), and 2-D layered (e.g., graphene, hexagonal boron nitride (h-BN), and MXenes) materials to separate and store tritium based on their diverse functionalities are discussed. Finally, the challenges and future directions for implementing tritium storage and separation are summarized in the reviewed materials.

Trapping of Small Molecules within Single or Double Cyclo[18]carbon Rings

The encapsulation of a set of small molecules, H₂, CO, CO₂, SO₂, and SO₃, by a circular C₁₈ ring is investigated by quantum calculations. These ligands lie near the center of the ring but, with the exception of H₂, are disposed roughly perpendicular to the ring plane. Their binding energies with the C₁₈ vary from 1.5 kcal/mol for H₂ up to 5.7 kcal/mol for SO₂, and the bonding is dominated by dispersive interactions spread over the entire ring. The binding of these ligands on the outside of the ring is weaker but allows the opportunity for each to bond covalently with the ring. A pair of C₁₈ units lie parallel to one another. This pair can bind each of these ligands in the area between them with only small perturbations of the double ring geometry. The binding energies of these ligands to this double ring configuration are amplified by some 50% compared to the single ring systems. The presented data concerning the trapping of small molecules may have larger implications regarding hydrogen storage or air pollution reduction.

Super Stable Pollution Gas Sensor Based on Functionalized 2D Boron Nitride Nanosheet Materials for High Humidity Environments

We report on studies of new gas sensing devices to be used in high humidity environments. Highly thermal-stable, super hydrophobic 2-dimensional (2D) boron nitride nanosheets (BNNSs) functionalized with Pt nanoparticles were prepared and used as an active layer for the prototype. The morphologic surface, crystallographic structures and chemical compositions of the synthesized 2D materials were characterized by using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) and Raman scattering, respectively. The experimental data reveals that high-quality BNNSs were prepared. A pair of Au electrodes were combined with a basic electrical circuit and the 2D sensing material to form high-performance gas sensors for the detection of pollution gases. The present structure is simple and the fabrication is easy and fast, which ensures the creation of a low-cost prototype with harsh (high humidity, high temperature) environment resistance and potential for miniaturization. The responses of the prototype to different target gases with different concentrations were characterized. The influences of the operating temperature and bias voltage effect on sensing performances were also investigated. The fabricated sensors appear to have high selectivity, high sensitivity and fast response to target gases. The sensing mechanism in the present case is attributed to the electron donation from the target gas molecules to the active layer, leading to the change of electrical properties on the surface of BNNS layer.

XH3 (X=P or N) Adsorption on Pristine, Pt-Doped and Vacancy-Defective (8,8) Boron Nitride Nanotubes: DFT Calculations

The adsorption energies (E ad), interaction distances, changes of geometric and electronic structures of XH3 (X=P or N) gas molecule adsorption on pristine, platinum (Pt) doped and vacancy-defected single-walled (8,8) boron nitride nanotubes (BNNTs) have been calculated using the density functional theory (DFT). The effect of the Pt doping on B and N sites (PtB,N-doped) and the B and N vacancy defects (VB,N-defected BNNT) on the sensing behavior of pristine (8,8) BNNTs toward PH3 and NH3 gases have been examined. According to the obtained results, PH3 and NH3 molecules were more likely to be absorbed on the PtB,N-doped and VN-defected BNNT with relatively higher E ad compared with the pristine and VB-defected BNNTs. Therefore the order of the obtained E ad were PtB-doped BNNT/NH3>PtB-doped BNNT/PH3>PtN-doped BNNT/NH3>PtN-doped BNNT/PH3 for the PtB,N-doped BNNTs, and VN-defected BNNT/NH3>VN-defected BNNT/PH3>VB-defected BNNT/NH3>VB-defected BNNT/PH3 for the VB , N-defected BNNTs systems. The partial density of states (PDOS) of the adsorption systems indicated the strong interaction between the adsorbed PH3 and NH3 molecules and the substrates, i.e. PtB,N-doped BNNT and VN-defected BNNT. Therefore, it can concluded that the PtB,N-doped and VN-defected BNNTs have potential applicability in the gas-sensing detection of PH3 and NH3 with good sensitivity.

Removal of Cr(iii)/Cr(vi) from wastewater using defective porous boron nitride: a DFT study

In this work, by using DFT calculation, we revealed that p-BN with vacancy defects could efficiently remove both Cr(iii) and Cr(vi) ions from an aqueous solution due to large E_ads values even in the higher Cr(iii)/Cr(vi) coverage.

On the H2 interactions with transition metal adatoms supported on graphene: a systematic density functional study

The attachment of H₂ to the full set of transition metal (TM) adatoms supported on graphene is studied by using density functional theory including dispersion, identifying physisorbed, Kubas, and dissociated states.

Boron nitride nanotubes: synthesis and applications

Boron nitride nanotube (BNNT) has similar tubular nanostructure as carbon nanotube (CNT) in which boron and nitrogen atoms arranged in a hexagonal network. Owing to the unique atomic structure, BNNT has numerous excellent intrinsic properties such as superior mechanical strength , high thermal conductivity, electrically insulating behavior, piezoelectric property, neutron shielding capability, and oxidation resistance. Since BNNT was first synthesized in 1995, developing efficient BNNT production route has been a significant issue due to low yield and poor quality in comparison with CNT, thus limiting its practical uses. However, many great successes in BNNT synthesis have been achieved in recent years, enabling access to this material and paving the way for the development of promising applications. In this article, we discussed current progress in the production of boron nitride nanotube, focusing on the most common and effective methods that have been well established so far. In addition, we presented various applications of BNNT including polymer composite reinforcement, thermal management packages, piezo actuators, and neutron shielding nanomaterial.

Introduction of carbon–boron atomic groups as an efficient strategy to boost formic acid production toward CO2electrochemical reduction

Introducing C–B diatomic groups in carbon-doped hexagonal boron nitride (h-BN) flakes resulted in high activity and selectivity for HCOOH in CO₂electroreduction.

Direct observation of site-selective hydrogenation and spin-polarization in hydrogenated hexagonal boron nitride on Ni(111)

We report the structural analysis and spin-dependent band structure of hydrogenated boron nitride adsorbed on Ni(111). The atomic displacement studied by using the normal incidence X-ray standing wave (NIXSW) technique supports the H-B(fcc):N(top) model, in which hydrogen atoms are site-selectively chemisorbed on boron atoms and N atoms remain on top of Ni atoms. The distance between the Ni plane and nitrogen plane did not change after hydrogenation, which implies that the interaction between Ni and N is 3d-π orbital mixing (donation and back-donation) even after hydrogenation of boron. The remaining π* peaks in near-edge X-ray absorption fine structure (NEXAFS) spectra are a manifestation of the rehybridization of sp² into sp³ states, which is consistent with the N-B-N bonding angle derived from NIXSW measurement. The SPMDS measurement revealed the spin asymmetry appearing on hydrogenated h-BN, which was originated from a π related orbital with back donation from the Ni 3d state. Even though the atomic displacement is reproduced by the density functional theory (DFT) calculation with the H-B(fcc):N(top) model, the experimental spin-dependent band structure was not reproduced by DFT possibly due to the self-interaction error (SIE). These results reinforce the site-selective hydrogenation of boron and pave the way for efficient design of BN nanomaterials for hydrogen storage.

Enhanced hydrogen adsorption on Li-coated B12C6N6

The hydrogen storage property of Li-coated B₁₂C₆N₆ is investigated by density functional theory calculations. B₁₂C₆N₆ is an electron deficient fullerene. Li atoms can be strongly bound to this cage by donating their valance electrons to the virtual 2p orbitals of carbon in the cluster. The binding energy (-2.90 eV) is much larger than the cohesive energy (1.63 eV) of bulk Li, and it prevents the Li atoms from aggregation. The coated Li atoms have large positive charges and the adsorbed hydrogen molecules can be moderately polarized by the Li⁺ ions. The computation shows that each Li atom coated on B₁₂C₆N₆ can hold 2-3 H₂ molecules with adsorption energies in the range of 0.21-0.24 eV/H₂. The B₁₂C₆N₆Li₈ can adsorb 16 H₂ and achieve a gravimetric hydrogen density of 8.63 wt. %. The present results indicate that alkali-metal atoms coated on electron deficient fullerenes can serve as hydrogen storage materials that can operate at ambient temperatures with high recycling storage capacity.

Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters

We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer.

A quantum chemistry study of curvature effects on boron nitride nanotubes/nanosheets for gas adsorption

Various boron nitride sheets interacting with noble gases, oxygen, and water on both sides of the surface were studied using high level DFT.

Influence of sumanene modifications with boron and nitrogen atoms to its hydrogen adsorption properties

We investigate the influence of sumanene modifications on its adsorption properties towards the hydrogen molecule.

A new strategy for hydrogen storage using BNNS: simultaneous effects of doping and charge modulation

The adsorption behavior of hydrogen molecule (H₂) on neutral and charged states of C-, Si- and P-doped boron nitride nanosheets (BNNSs), is investigated using density functional theory (DFT) method.

Porous boron nitride with a high surface area: hydrogen storage and water treatment

We report on the synthesis of high-quality microporous/mesoporous BN material via a facile two-step approach. An extremely high surface area of 1687 m(2) g(-1) and a large pore volume of 0.99 cm(3) g(-1) have been observed in the synthesized BN porous whiskers. The formation of the porous structure was attributed to the group elimination of organic species in a BN precursor, melamine diborate molecular crystal. This elimination method maintained the ordered pore structure and numerous structural defects. The features including high surface area, pore volume and structural defects make the BN whiskers highly suitable for hydrogen storage and wastewater treatment applications. We demonstrate excellent hydrogen uptake capacity of the BN whiskers with high weight adsorption up to 5.6% at room temperature and at the relatively low pressure of 3 MPa. Furthermore, the BN whiskers also exhibit excellent adsorption capacity of methyl orange and copper ions, with the maximum removal capacity of 298.3 and 373 mg g(-1) at 298 K, respectively.

Theoretical study on the encapsulation of Pd3-based transition metal clusters inside boron nitride nanotubes

Chemical functionalization of the boron nitride nanotube (BNNT) allows a wider flexibility in engineering its electronic and magnetic properties as well as chemical reactivity, thus making it have potential applications in many fields. In the present work, the encapsulation of 13 different Pd(3)M (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Pt, and Au) clusters inside the (10, 0) BNNT has been studied by performing comprehensive density functional theory (DFT) calculations. Particular attention is paid to searching for the stable configurations, calculating the corresponding binding energies, and evaluating the effects of the encapsulation of Pd(3)M cluster on the electronic and magnetic properties of BNNT. The results indicate that all the studied Pd(3)M clusters can be stably encapsulated inside the (10, 0) BNNT, with binding energies ranging from -0.96 (for Pd(3)Sc) to -5.31 eV (for Pd(3)V). Moreover, due to a certain amount of charge transfer from Pd(3)M clusters to BNNT, certain impurity states are induced within the band gap of pristine BNNT, leading to the reduction of the band gap in various ways. Most Pd(3)M@BNNT nanocomposites exhibit nonzero magnetic moments, which mainly originate from the contribution of the Pd(3)M clusters. In particular, the adsorption of O(2) molecule on BNNT is greatly enhanced due to Pd(3)M encapsulation. The elongation of O-O bonds of the adsorbed O(2) molecules indicates that Pd(3)M@BNNT could be used to fabricate the oxidative catalysis.

Graphane nanotubes

In this work, one-dimensional graphane nanotubes (GN, stoichiometry CH), built from 2D single-sheet graphanes, are explored theoretically. Zigzag type GN(10,0) and armchair type GN(10,10) structures with varying surface termination were investigated in detail. GN(10,10)-A is found to be the most stable configuration among the GN structures considered. An annealing analysis indicates that graphane-A and GN(10,10)-A are likely to be stable at elevated temperature. A possible reaction path to GN(10,10)-A is suggested by the reaction of single-walled carbon nanotube (10,10) + H(2); the indications are that the GN(10,10)-A can be made at low temperature and high partial pressure of H(2) gas from the corresponding nanotube. The graphane nanotubes are predicted to be wide band gap insulators. A study of the effect of the diameter of GN structures shows, unexpectedly, that the gap increases on reducing the diameter of the graphane nanotubes. We also investigated several partially hydrogenated graphenes and single-walled carbon nanotubes (SWNT); the greater hydrogenation is, the more stable is the resulting structure. The band gap of graphene or SWNT can be tuned via hydrogenation.

Carbon-tuned bonding method significantly enhanced the hydrogen storage of BN-Li complexes

Through first-principles calculations, we found doping carbon atoms onto BN monolayers (BNC) could significantly strengthen the Li bond on this material. Unlike the weak bond strength between Li atoms and the pristine BN layer, it is observed that Li atoms are strongly hybridized and donate their electrons to the doped substrate, which is responsible for the enhanced binding energy. Li adsorbed on the BNC layer can serve as a high-capacity hydrogen storage medium, without forming clusters, which can be recycled at room temperature. Eight polarized H(2) molecules are attached to two Li atoms with an optimal binding energy of 0.16-0.28 eV/H(2), which results from the electrostatic interaction of the polarized charge of hydrogen molecules with the electric field induced by positive Li atoms. This practical carbon-tuned BN-Li complex can work as a very high-capacity hydrogen storage medium with a gravimetric density of hydrogen of 12.2 wt%, which is much higher than the gravimetric goal of 5.5 wt % hydrogen set by the U.S. Department of Energy for 2015.

Doping of alkali, alkaline-earth, and transition metals in covalent-organic frameworks for enhancing CO2 capture by first-principles calculations and molecular simulations

We use the multiscale simulation approach, which combines the first-principles calculations and grand canonical Monte Carlo simulations, to comprehensively study the doping of a series of alkali (Li, Na, and K), alkaline-earth (Be, Mg, and Ca), and transition (Sc and Ti) metals in nanoporous covalent organic frameworks (COFs), and the effects of the doped metals on CO2 capture. The results indicate that, among all the metals studied, Li, Sc, and Ti can bind with COFs stably, while Be, Mg, and Ca cannot, because the binding of Be, Mg, and Ca with COFs is very weak. Furthermore, Li, Sc, and Ti can improve the uptakes of CO2 in COFs significantly. However, the binding energy of a CO2 molecule with Sc and Ti exceeds the lower limit of chemisorptions and, thus, suffers from the difficulty of desorption. By the comparative studies above, it is found that Li is the best surface modifier of COFs for CO2 capture among all the metals studied. Therefore, we further investigate the uptakes of CO2 in the Li-doped COFs. Our simulation results show that at 298 K and 1 bar, the excess CO2 uptakes of the Li-doped COF-102 and COF-105 reach 409 and 344 mg/g, which are about eight and four times those in the nondoped ones, respectively. As the pressure increases to 40 bar, the CO2 uptakes of the Li-doped COF-102 and COF-105 reach 1349 and 2266 mg/g at 298 K, respectively, which are among the reported highest scores to date. In summary, doping of metals in porous COFs provides an efficient approach for enhancing CO2 capture.

Computational studies on hydrogen storage in aluminum nitride nanowires/tubes

One-dimensional AlN nanowires/tubes were exploited as hydrogen storage media. The adsorption of atomic and molecular hydrogen on AlN nanowires was investigated by using density functional theory computations. Hydrogen atoms prefer to adsorb on top of neighboring threefold-coordinated N and Al atoms in pairs. A hydrogen molecule, however, prefers to adsorb on top of threefold-coordinated Al atoms in the nanowire surface, with an adsorption energy of 0.21 eV. H(2) dissociation is exothermic in the surface of AlN nanowires, and the dissociation barrier is rather low (0.76 eV), indicating that chemisorption is a feasible route for hydrogen storage in AlN nanowires/tubes. A maximum 3.66 wt% of molecular and 2.44 wt% of atomic hydrogen can be stored in AlN nanowires/tubes.