High-temperature Desorption Research Articles

Enhancing hydrogen desorption in MgH2: A DFT study on the effects of copper and zinc doping

Magnesium hydride (MgH2) stands out as a promising hydrogen storage material due to its high capacity, but faces challenges such as high desorption temperatures. This study employs density functional theory (DFT) calculations to explore the impact of copper (Cu) and zinc (Zn) doping on MgH2. We find that Cu doping, particularly at 12.5 wt%, significantly reduces the activation energy for hydrogen desorption to 65.2 kJ/mol, a marked improvement over pure MgH2. Conversely, Zn doping shows varied effects with higher activation energies observed across different concentrations. These results underscore Cu's potential as a catalyst to enhance hydrogen release kinetics in MgH2, offering insights crucial for optimizing hydrogen storage technologies. This research contributes to advancing the understanding and application of MgH2-based systems for efficient hydrogen utilization in sustainable energy solutions.

Addressing small-scale temperature swing adsorption challenges using intensified fluidised bed technology for carbon capture process development

Polyethylenimine (PEI)-based adsorbents exhibit high CO2 capacities, making them potential candidates for mitigating unavoidable industrial CO2 emissions. However, desorption of CO2 from PEI, and from adsorbents in general, has received far less attention in the literature than adsorption. Whilst Temperature Swing Adsorption (TSA) is simple to conceptualise, it is difficult to implement in small-scale experiments in practice. Here we study the desorption characteristics of a commercial branched PEI adsorbent in a small-scale swirling fluidised bed reactor (TORBED) to improve the small-scale heat transfer rates. Our experimental results show that higher desorption temperatures, higher gas flow rates, and higher CO2 concentrations during adsorption can improve the desorption efficiency (defined as the amount of CO2 removed as a fraction of the initial amount adsorbed). In terms of kinetics, we found that the fractional order kinetic model provided the best fit to the PEI adsorbent, implying that this adsorbent involves multiple simultaneous molecular interactions, physisorption processes, and chemisorption processes, that cannot be described by simpler pseudo 1st or 2nd order models. Desorption rates in the TORBED in this study were 1 order of magnitude faster than fluidised beds, and 2–3 orders of magnitude faster than packed beds.

Facilitated hydrogen storage properties of MgH2 by Ni nanoparticles anchored on Mo2C@C nanosheets

Magnesium hydride (MgH2) holds promise as a hydrogen storage material, but its practical application is impeded by high desorption temperatures and slow kinetics, presenting substantial challenges. Herein, an efficient approach is proposed to synthesize Mo2C@C nanosheets-supported Ni nanoparticles (Ni/Mo2C@C-2) materials, which can operate as a highly efficient catalyst to enhance hydrogen desorption of MgH2. The ball-milled MgH2–7.5 wt% Ni/Mo2C@C-2 demonstrates prominent hydrogen desorption kinetics with an activation energy (Ea) of 97.22 kJ mol−1, alongside remarkable cycling stability, maintaining a capacity retention of 97.8% after 20 cycles. Consequently, the results reveal that the improvement of hydrogen storage properties for MgH2 can be attributed to the synergistic effect of the in-situ generated Mg2NiH4 with highly dispersion, the sustained Mo2C nanosheets, and highly graphitized carbon. This work provides a reliable strategy for constructing polyoxometalates derivatives to facilitate the hydrogen desorption and cycling of MgH2.

Diaminopropane-Functionalized Metal-Organic Frameworks with Controllable Diamine Loss and One-Channel Flipped CO2 Adsorption Mode.

Diamine-functionalized metal-organic frameworks (MOFs) based on Mg2(dobpdc) (dobpdc4- = 4,4'-dioxidobihyenyl-3,3'-dicarboxylate) have been frequently reported as promising CO2 adsorbents due to their characteristic step-shaped adsorption behavior. However, high CO2 desorption temperatures for diamine-Mg2(dobpdc)-based adsorbents led to gradual diamine loss while the existence of an exotic CO2 adsorption mode remains experimentally unanswered. Herein, we present CO2 adsorbents obtained by functionalizing Mn2(dobpdc) with a diaminopropane series. These adsorbents offer low regeneration energies, allowing CO2 desorption at lower temperatures than the reported Mg-based analogs. Our first-principles density functional theory calculations showed that the binding strength between the diamine and Mn ions in Mn2(dobpdc) was stronger than that between the diamine and Mg ions in Mg2(dobpdc), preventing diamine loss even at high temperatures and enabling efficient regeneration. Additionally, the computational and experimental data demonstrated that primary-tertiary diamine-functionalized MOFs exhibit one-channel flipped adsorption structures that have not been experimentally revealed. Our findings provide insights into the role of metal ions in diamine loss for the future development of efficient amine-based CO2 adsorbents.

X[formula omitted]CoH[formula omitted] (X = Ca, Sr) for hydrogen storage: First-principles computations

The structural, electronic, elastic, optical, phonon, and thermo-physical properties of the tetragonal X2CoH5 (X = Ca, Sr) hydrogen storage compounds were thoroughly examined using first-principles calculations. The negative formation enthalpies (−76.03 kJ/mol.H2 for Ca2CoH5 and −72.55 kJ/mol.H2 for Sr2CoH5) highlight the structural stability of these materials. Phonon calculations revealed no imaginary frequency modes, confirming the dynamic stability of X2CoH5. The mechanical stability of Ca2CoH5 and Sr2CoH5 was evidenced by the compliance of the elastic constants with Born stability criteria. The electronic band structure indicates that Ca2CoH5 and Sr2CoH5 are direct bandgap semiconductors with narrow bandgaps of ∼0.27 and 0.34 eV, respectively. The appraisal of Poisson’s ratio (ν = 0.22 for X = Ca and 0.23 for Sr) and Pugh’s ratio (B/G = 1.47 for X = Ca and 1.56 for Sr) suggests that both metal hydrides exhibit brittle mechanical behavior. Moreover, 3D plots of Young’s modulus (E), shear modulus (G), linear compressibility (β), and Poisson’s ratio (ν) uncover anisotropy within X2CoH5. The hydrogen storage capabilities were scrutinized, and the present materials feature excellent volumetric hydrogen density (95.65 gH2l−1 for Ca2CoH5 and 80.24 gH2l−1 for Sr2CoH5), moderate gravimetric hydrogen density (3.38 wt% for Ca2CoH5 and 2.06 wt% for Sr2CoH5) and high hydrogen desorption temperature (584 K for Ca2CoH5 and 558 K for Sr2CoH5). Notably, the obtained volumetric hydrogen densities are in line with the volumetric capacity criteria set by the U.S. Department of Energy (DOE) for 2025. Finally, the optical and thermo-physical characteristics of X2CoH5 compounds were also investigated in this work.

Economic and environmental benefits of novel process of ionic liquids-based toluene absorption from exhaust gas at atmospheric pressure

The traditional toluene absorption process typically operates at high absorption pressure and desorption temperature, imposing a significant burden on the process. In this work, a novel process of atmospheric pressure toluene absorption using ionic liquids (ILs) is first proposed, which involves introducing a stripping column after the desorption unit to perform secondary purification of the circulating ILs, further decreasing the toluene content in ILs from 106–215 ppm to 5–13 ppm. Moreover, the novel process reduces the absorption pressure from 18 bar to 1 bar, and decreases the desorption temperature from 310 °C to approximately 150 °C. A comprehensive comparison of the traditional and novel process is carried out using nine ILs composed of imidazolium cations ([BMIM]+, [HMIM]+, [OMIM]+) and anions ([BF4]-, [PF6]-, [NTf2]-), considering both process economics and life cycle environmental impacts. The results indicate that in comparison to the traditional process using same ILs, the proposed novel processes exhibit superior economic performance and lower environmental impact, achieving savings of 68.9–76.9% in total annual cost and reducing global warming potential by 56.4–74.8%.

Advancing Catalysts by Nanoconfinement and Catalysis for Enhanced Hydrogen Production from Magnesium Borohydride: A Review.

Hydrogen storage in solid-state materials represents a promising avenue for advancing hydrogen storage technologies, driven by their potential for high efficiency, reduced risk, and cost-effectiveness. Among the employed materials, magnesium borohydride (Mg(BH4)2) stands out for its exceptional characteristics, with a gravimetric capacity of 14.9 wt% and a volumetric hydrogen density capacity of 146 kg/m3. However, the practical application of Mg(BH4)2 is impeded by challenges such as high desorption temperatures (≥ 270 °C), sluggish kinetics, poor reversibility, and the formation of unexpected byproducts like diborane. To address these limitations, extensive research efforts have been directed towards enhancing the hydrogen storage properties of Mg(BH4)2. Various strategies have been explored, including incorporating catalysts or additives, nanoconfinement of Mg(BH4)2 within porous supports, and modifications involving metal alloys and compositional adjustments. These approaches are actively under investigation for improving the performance of Mg(BH4)2-based hydrogen storage systems. This review provides a comprehensive survey of recent advancements in Mg(BH4)2 research, focusing on experimental findings related to nanoconfined Mg(BH4)2 and modified thermodynamic processes aimed at enabling hydrogen release at lower temperatures by mitigating sluggish kinetics. Precisely, nanostructuring techniques, catalyst-mediated nanoconfinement methodologies, and alloy/compositional modifications will be elucidated, highlighting their potential to enhance hydrogen storage properties and overcome existing limitations. Furthermore, this review also discusses the challenges encountered in utilizing Mg(BH4)2 for hydrogen storage applications and offers insights into the prospects of this material. By synthesizing the latest research findings and identifying areas for further exploration, this review aims to contribute to the ongoing efforts toward realizing the full potential of Mg(BH4)2 as a viable solution for hydrogen storage in diverse applications.

Enhancing the CO2 Adsorption of the Cobalt-Free Layered Perovskite Cathode for Solid-Oxide Electrolysis Cells Gains Excellent Stability under High Voltages via Oxygen-Defect Adjustment.

Solid-oxide electrolysis cells are a clean energy conversion device with the ability to directly electrolyze the conversion of CO2 to CO efficiently. However, their practical applications are limited due to insufficient CO2 adsorption performance of the cathode materials. To overcome this issue, the A-site cation deficiency strategy has been applied in a layered perovskite PrBaFe1.6Ni0.4O6-δ (PBFN) cathode for direct CO2 electrolysis. The introduction of 5% deficiency at the Pr/Ba site leads to a significant increase in the concentration of oxygen vacancies (nonstoichiometric number δ of oxygen vacancies increased from 0.093 to 0.132), which greatly accelerates the CO2 adsorption performance as well as the O2- transport capacity toward the CO2 reduction reaction (CO2RR). CO2 temperature-programmed desorption indicates that A-site cation-deficient (PrBa)0.95Fe1.6Ni0.4O6-δ (PB95FN) shows a larger desorption peak area and a higher desorption temperature. PB95FN also exhibits a greater presence of carbonate in Fourier transform infrared (FT-IR) spectroscopy. The electrical conductivity relaxation test shows that the introduction of the 5% A-site deficiency effectively improves the surface oxygen exchange and diffusion kinetics of PB95FN. The current density of the electrolysis cell with the (PrBa)0.95Fe1.6Ni0.4O6-δ (PB95FN) cathode reaches 0.876 A·cm-2 under 1.5 V at 800 °C, which is 41% higher than that of PB100FN. Moreover, the PB95FN cathode demonstrates excellent long-term stability over 100 h and better short-term stability than PB100FN under high voltages, which can be ascribed to the enhanced CO2 adsorption performance. The PB95FN cathode maintains a porous structure and tightly binds to the electrolyte after stability testing. This study highlights the potential of regulating oxygen defects in layered perovskite PrBaFe1.6Ni0.4O6-δ cathode materials via incorporation of cation deficiency toward high-temperature CO2 electrolysis.

Machine learning insights into prediction of H2 gravimetric capacity in Mg-based pure metal alloys

Hydrogen is emerging as a crucial clean energy carrier, but storage challenges remain. Magnesium has the highest hydrogen storage capacity among metals, yet its high thermodynamic stability, desorption temperature, and slow reaction rates hinder practical use. Identifying suitable metal alloys for magnesium remains challenging. This study employs ML-framework with 13 inputs to predict H2 storage and release capacity (2 outputs) in Mg-based alloys, with database comprises 792 storage and 279 release observations. Linear-models initially performed poorly, leading to the development of nonlinear models such as tree ensembles, kernel based methods, and neural networks. After hyperparameter tuning with 5-fold cross-validation, an ANN with Bayesian regularization achieved higher accuracy in predicting hydrogen gravimetric capacity (R2 = 0.86 for storage, R2 = 0.93 for release for test data). With this model, post-analysis revels key-factors influencing hydrogen uptake are particle size, Mg composition, and pressure, while temperature and time significantly affect hydrogen release. Finally, this study identifies operating ranges for these factors, providing insights for improving/accelerating Mg based hydrogen storage materials development.

First-principles calculations to investigate Mg3XH8 (X = Ca, Sc, Ti, V, Cr, Mn) materials for hydrogen storage

An ideal hydrogen storage material is a key topic in efficient hydrogen energy utilization. We have explored several potential hydrogen storage materials Mg3XH8 (X = Ca, Sc, Ti, V, Cr, Mn) by first-principles calculations. The studied materials all belong to lightweight hydrogen storage materials. The normal phonon dispersion spectrum indicates, without regard to other materials, at least Mg3TiH8 and Mg3VH8 are completely stable in dynamics, which is also demonstrated by elastic stability criteria. The elastic properties show that they are all ductile materials with the applicable potential in flexible fields. Besides, they are gapless and metallic in band structures. With the correction of Hubbard values, all transition metal based Mg3XH8 materials are magnetic materials with magnetic moments of 0.34 μB for Mg3ScH8, and 2.14 μB for Mg3TiH8, 1.29 μB for Mg3TiH8, 2.65 μB for Mg3TiH8 and 4.86 μB for Mg3MnH8, respectively. Whereas Mg3CrH8 and Mg3MnH8 exhibit highly light active in infrared and visible region. Considering overall structural stability, excellent mechanical properties, high gravimetric hydrogen density (6.21% and 6.07%) and moderate hydrogen desorption temperature (∼350 K), Mg3TiH8 and Mg3VH8 are considered as the candidates for promising hydrogen storage materials. Besides, Due to half-metallic nature, they are also potential in spin electronic devices.

Recent Advances in the Preparation Methods of Magnesium-Based Hydrogen Storage Materials.

Magnesium-based hydrogen storage materials have garnered significant attention due to their high hydrogen storage capacity, abundance, and low cost. However, the slow kinetics and high desorption temperature of magnesium hydride hinder its practical application. Various preparation methods have been developed to improve the hydrogen storage properties of magnesium-based materials. This review comprehensively summarizes the recent advances in the preparation methods of magnesium-based hydrogen storage materials, including mechanical ball milling, methanol-wrapped chemical vapor deposition, plasma-assisted ball milling, organic ligand-assisted synthesis, and other emerging methods. The principles, processes, key parameters, and modification strategies of each method are discussed in detail, along with representative research cases. Furthermore, the advantages and disadvantages of different preparation methods are compared and evaluated, and their influence on hydrogen storage properties is analyzed. The practical application potential of these methods is also assessed, considering factors such as hydrogen storage performance, scalability, and cost-effectiveness. Finally, the existing challenges and future research directions in this field are outlined, emphasizing the need for further development of high-performance and cost-effective magnesium-based hydrogen storage materials for clean energy applications. This review provides valuable insights and references for researchers working on the development of advanced magnesium-based hydrogen storage technologies.

Investigation for the hydrogen storage properties of XCrH3 (X=Na, K) and KYH3(Y[dbnd]Mo, W) perovskite type hydrides based on first-principles

Perovskite type hydrides have emerged as a focal point in hydrogen storage applications as potential candidates in recent years. However, the currently synthesized perovskite hydrogen storage materials suffer from high hydrogen desorption temperatures and unstable reactions. To identify promising perovskite hydrogen storage materials, this study explores the hydrogen storage properties of XCrH3 (X = Na, K) and KYH3 (YMo, W) based on first-principles (FPs) calculations. The results indicate that NaCrH3 and KCrH3 exhibit half-metallic properties, while KMoH3 and KWH3 are metallic materials with high hydrogen storage safety. Mechanical property analysis reveals that NaCrH3 exhibits the highest hardness, indicating better stability for hydrogen storage. Thermodynamic analysis shows that KCrH3 has a lower hydrogen desorption temperature than the other three compounds, with NaCrH3 having the second-lowest. The gravimetric hydrogen storage capacities of NaCrH3, KCrH3, KMoH3, and KWH3 are 3.85 wt%, 3.21 wt%, 2.19 wt%, and 1.34 wt%, respectively. Overall, NaCrH3 demonstrates superior gravimetric hydrogen storage capacity, stability, and safety, making it a promising candidate for new perovskite type hydrogen storage materials.

Sc-Modified C3N4 Nanotubes for High-Capacity Hydrogen Storage: A Theoretical Prediction.

Utilizing hydrogen as a viable substitute for fossil fuels requires the exploration of hydrogen storage materials with high capacity, high quality, and effective reversibility at room temperature. In this study, the stability and capacity for hydrogen storage in the Sc-modified C3N4 nanotube are thoroughly examined through the application of density functional theory (DFT). Our finding indicates that a strong coupling between the Sc-3d orbitals and N-2p orbitals stabilizes the Sc-modified C3N4 nanotube at a high temperature (500 K), and the high migration barrier (5.10 eV) between adjacent Sc atoms prevents the creation of metal clusters. Particularly, it has been found that each Sc-modified C3N4 nanotube is capable of adsorbing up to nine H2 molecules, and the gravimetric hydrogen storage density is calculated to be 7.29 wt%. It reveals an average adsorption energy of -0.20 eV, with an estimated average desorption temperature of 258 K. This shows that a Sc-modified C3N4 nanotube can store hydrogen at low temperatures and harness it at room temperature, which will reduce energy consumption and protect the system from high desorption temperatures. Moreover, charge donation and reverse transfer from the Sc-3d orbital to the H-1s orbital suggest the presence of the Kubas effect between the Sc-modified C3N4 nanotube and H2 molecules. We draw the conclusion that a Sc-modified C3N4 nanotube exhibits exceptional potential as a stable and efficient hydrogen storage substrate.

Surface blistering and D desorption in high-energy-rate forging W, W-Y2O3, W-TiC exposed to deuterium plasma

Pure tungsten (W) and two representative W alloys of W-1 wt.%Y2O3 and W-0.5 wt.%TiC were subjected to deuterium (D) plasma exposure at a fluence up to 1 × 1026 D/m2 at 400 K to evaluate their surface blistering and D desorption behaviors. Thermal desorption spectroscopy (TDS) results revealed that high-temperature desorption peaks (> 650 K) dominated in HERF-W, whereas the two W alloys featured higher intensities of low-temperature D desorption peaks (< 650 K). Even at a low D implantation fluence of 5 × 1023 D/m2, extensive blisters were evident on the surface of pure W, while no discernible blisters were detected on the surface of W-1 wt.%Y2O3 and W-0.5 wt.%TiC, even with a fluence exceeding 2 × 1025 D/m2. Microstructure analysis indicated that the relatively large grain size and limited intrinsic defects in HERF-W were the primary reasons for the early formation of D-induced blisters and subsequent high-temperature desorption of these trapped D, compared to those of two other W alloys. A focus ion beam (FIB)-SEM technique was employed to explore the mechanisms of blistering. Results revealed that the cavities beneath blisters were primarily located along grain boundaries, and coarse blisters were formed by the merging of several small ones. This work provides insight into the relationships among material microstructures, D-induced blistering and D desorption in W-based materials, thus offering valuable guidance for the design of W materials with high resistance to D-induced damages.

Fluorine, nitrogen doping, and triaxial strain effects on the structural stability and hydrogen storage properties of lithium hydride LiH: DFT investigation

This research comprehensively addressed various aspects of hydrogen storage, with a focus on metallic hydride materials, lithium hydride LiH, one of the lightest reversible metal hydrides, boasts a remarkable gravimetric density of up to 12.67 wt% and an impressive volumetric capacity of 4.95 Kg/100 L. Despite these strengths, challenges accompany lithium hydride, such as its elevated formation energy and a high desorption temperature around 600 K–700 K. In this work, ab initio calculations based on Density Functional Theory (DFT) were used to study the thermodynamic and electronic properties of this material with the aim of reducing the high temperature of decomposition while preserving a significant gravimetric capacity and satisfactory stability in line with the U.S. Department of Energy (DOE) standards for solid-state hydrogen storage (ΔHf = - 40 kJ/mol.H2 and Td = 289 K–393 K). The results obtained show the influence of the doping effect firstly (Li1-xFxH, Li1-xNxH) on the improvement of the hydrogen storage properties, with a percentage gain of 50.64% for 4% doping with F and 49.08% for 8% doping with N. Secondly, a 38.63% gain in thermodynamic stability was observed by applying triaxial compressive stresses to the LiH compound.

Experimental study of the new composite materials for thermochemical energy storage

Thermochemical energy storage (TCES) is a promising technology to support the world's initiatives to reduce CO2 emissions and limit global warming. In this paper, we have synthesized and characterized a new three-component composite materials consisting of a mixture of calcium chloride and iron powder confined inside the expanded vermiculite. The new approaches of studying composite sorbents of ammonia using a gas flow-through microcalorimetry proposed in this work. The energetics of adsorption as a function of ammonia uptake was measured at room temperature (RT), 106 and 150 °C. The enthalpy of NH3 sorption in eight cycles tested ranged from 12.2 to 39.1 kJ mol−1. The strength of ammonia sorption on composite surface was characterized by TPD (Temperature Programmed Desorption). Based on the NH3-TPD profiles of composites it was found that the high-temperature desorption peaks of vermiculite sample shifted to lower temperature after the deposition of salt. The characterization of the composites was complemented by the laboratory analyses using XRD, WD-XRF, FTIR, TG/DTG, SEM-EDS and nitrogen sorption isotherms at −196 °C (BET method). The composite impregnated with 37 wt% of salt has the highest enthalpy and sorption capacity, thus seems to be the most promising candidates for the heat storage systems.

Li decorated graphene like MgN4 monolayer for hydrogen storage: A first-principles approach

The rapid advancement of hydrogen storage materials possessing high storage capacity, long life-cycle, reversibility, and rapid kinetics is a trending issue. Metal decoration of a two-dimensional material is a successful method of enhancing hydrogen storage capacity. Li-decorated 2D MgN4 has been inspected as a hydrogen storage material for practical applications employing density functional theory simulations. Our findings indicate that the substrate (LiMgN4) may adsorb up to 6 molecules of H2 with a gravimetric storage capacity of 1.83 wt.%, making it a viable choice for storage medium. With an average adsorption energy of 0.21 eV per H2, hydrogen is effectively sensed by Li-augmented MgN4 monolayer. Additionally, two-sided Li-decoration is discussed with 12 H2 adsorbed on each side with a storage capacity of 6.86 wt.% with an average adsorption energy of 0.15 eV/H2. High desorption temperature confirms the effective desorption of H2 from the substrate. The Li-decorated porous MgN4 responds effectively in the adsorbate (H2) environment. The predicted adsorption energy, recovery time and desorption temperature demonstrate that LiMgN4 is an exceptional choice for energy storage devices.

Adsorption Mechanism of Methylene Blue on Purified Red Phosphorus and Effects of Different Temperatures on Methylene Blue Desorption

Purified red phosphorus (RP) can be used as an adsorbent. However, the adsorption mechanism and reuse ability of purified RP have not been reported. This study utilized X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy techniques (a statistical physics model and the standard molar free energy of formation) to investigate the adsorption mechanism of methylene blue (MB) by purified RP. Purification did not change commercial RP structure according to X-ray diffraction. The results showed that the adsorption process only included physical adsorption according to Fourier transform infrared spectroscopy and UV–vis diffuse reflection absorption spectra. The specific areas of commercial RP and purified RP were 0.02 cm3/g and 5.27 cm3/g, respectively. Thus, purified RP has a higher adsorption capacity compared with commercial RP. A statistical physics model showed that, as the temperature increased from 288 to 308 K, the qe, Dm and qsat of purified RP for MB increased from 179.87, 0.824 and 0.824 to 303.26 mg/g, 1.497 mol/kg and 1.497 mol/kg, respectively. The fitted values of ΔrSmθ, ΔrHmθ and ΔrGmθ were 104.38 J·mol−1·K−1, −2.7 × 103 J·mol−1 and negative, respectively. Thus, according to adsorption energy, the adsorption of MB by purified RP was a spontaneous process, which was mainly driven by entropy increasing. Compared with neutral dye, the purified RP had higher adsorption ability for the cationic dye and anionic dye. As the purified RP dose increased from 30 to 150 mg, the adsorption capacity of purified RP increased. However, as the MB concentration and pH increased, the adsorption capacity of purified RP decreased. The purified RP had excellent reuse ability and high temperature desorption can be applied to obtain its reuse ability.

Improving the desorption properties of LiAlH4 by the addition of Ni0.6Zn0.4O

Lithium alanate (LiAlH4) is one of the most preferred materials for solid-state hydrogen storage materials owing to its relatively high hydrogen capacity (10.5 wt%). However, its high decomposition temperature and sluggish desorption kinetic restrict its potential application as a hydrogen storage medium for on-board hydrogen-powered applications. To overcome these problems, the impacts of Ni0.6Zn0.4O synthesized via a solid-state method on the desorption properties of LiAlH4 have been examined in this study. It was found that after the introduction of 10 wt% of Ni0.6Zn0.4O to LiAlH4, hydrogen started to release at 124 °C and 170 °C for the first two stages, respectively. Isothermal desorption kinetics also revealed that faster desorption kinetics can be observed at 90 °C for 120 min LiAlH4+10 wt% of Ni0.6Zn0.4O can desorb 3.1 wt% of H2, whereas undoped LiAlH4 can release approximately less than 0.5 wt% of H2 in the same time frame. According to the Kissinger method, the apparent activation energies for the first two steps of the LiAlH4+10 wt% of Ni0.6Zn0.4O composites have been found to be 73 kJ/mol and 85 kJ/mol, respectively, 32 kJ/mol and 40 kJ/mol less than milled LiAlH4. The in-situ formation of NiO and Zn or Zn-containing compounds during the heating process might contribute to the kinetic improvement of LiAlH4.

In Ukrainian

Thermal destruction of composites of ureaformaldehyde (UPR) and polyester resins (PER) with silicon dioxide nanoparticles having a specific surface area of 280 m2/g, titanium dioxide and titanosilicate with a specific surface area of 40 and 48 m2/g, respectively, when a filler content is no more than 5.0 wt% have been studied. The investigations were performed using The thermally programmed mass spectrometry method with registration of the masses of desorbed atomic fragments in the 10 ‒ 200 m/z range. It was established that during the main polymer mass destruction at 150 ‒ 350 oC, along with low temperature decomposition products, anomalously high thermal resistance of a number of atomic fragments of polymer chains and cross-links are recorded. The atomic composition of destruction fragments and their desorption temperature in the range 400 ‒ 700 oС were determined. It was established that in composites of ureaformaldehyde resin with SiO2 and TiO2 nanoparticles the high temperature resistance of fragments with m/z 27 exhibits due to the formation of strong bonds among the Si and Ti surface sites and the nitrogen atoms of the polymer. Such thermal stability is not realized in resin loading with (Si/Ti)O2 nanoparticles. In composites of polyester resin with silica a high-temperature destruction of oxygen atoms from polyester chains realizes at temperatures of 290 ‒ 400 oC and a low-intensity wide destruction band takes place in the temperature range 400 ‒ 700 oC. In addition, in the temperature range of 400-700 oC cross-links are destroyed with the release of benzene rings and styrene molecules. It was established that anomalously high-temperature desorption is typical for atomic fragments of the polymer structure attached to surface Si and Ti sites through nitrogen or carbon atoms from the polymer structure. Thus, in UPR composites with silicon and titanium oxides, strong chemical nitride bonds of the form Si-N≡C-H and Ti-N≡C-H are formed, which demonstrate anomalously high heat resistance. It is shown that in composites of polyester resin with silicon dioxide nanoparticles, the high-temperature destruction of fragments is due to their desorption from the surface of silicon dioxide particles when breaking their bonds with silicon atoms. Thus, polymer matrices have been determined, in which atomic fragments of the macromolecule, binding to the surface centers of fillers, significantly weaken the thermal destruction of composites due to the formation of strong chemical and coordination bonds.