High Hydrogen Content Research Articles

Towards hydrogen-rich ionic (NH4)(BH3NH2BH2NH2BH3) and related molecular NH3BH2NH2BH2NH2BH3.

Attempts of the synthesis of ionic (NH4)(BH3NH2BH2NH2BH3) via a metathetical approach resulted in a mixture of the target compound and partly dehydrogenated molecular NH3BH2NH2BH2NH2BH3 product. The mixed specimen was characterised by NMR and vibrational spectroscopies, and the cocrystal structure was analyzed from powder X-ray diffraction data supported by theoretical density functional theory calculations. The compound crystallises in a P21/c unit cell with the lattice parameters of a = 13.401(11) Å, b = 13.196(8) Å, c = 17.828(12) Å, β = 128.83(4)°, V = 2556(3) Å3 and Z = 16. Despite their impressive hydrogen content, similar to ammonia borane, both title compounds release hydrogen substantially polluted with borazine and traces of ammonia and diborane.

Chromic hydroxide-decorated palladium nanoparticles confined by amine-functionalized mesoporous silica for rapid dehydrogenation of formic acid.

Formic acid (FA), one of the products of biomass conversion and CO2 reduction, has attracted much attention as a renewable liquid hydrogen carrier with a high hydrogen content (4.4wt%). Searching for efficient catalysts to realize hydrogen evolution from FA are highly desired but challenging. Herein, ultrafine and mono-dispersed Pd-Cr(OH)3 nanoparticles (1.3nm) loaded on amine-functionalized mesoporous silica (AFMS) have been prepared and applied as an effective catalyst for rapid hydrogen production from additive-free FA. The as-synthesized Pd-Cr(OH)3/AFMS catalysts exhibited efficient catalytic activity and 100% hydrogen selectivity and conversion toward FA dehydrogenation reaction without additives, giving an initial TOF value of 3112h-1 at 323K, which is comparable to most of the highly efficient heterogeneous catalysts reported so far under similar reaction conditions. This work provides a feasible idea for the design metal hydroxide-modified Pd-based efficient heterogeneous catalyst, which is expected to enhance the application of FA in fuel cells.

Structural stability, dihydrogen bonding, and pressure-induced polymorphic transformations in hydrazine borane.

Hydrazine borane (N2H4BH3) has attracted considerable interest as a promising solid-state hydrogen storage material owing to its high hydrogen content and easy preparation. In this work, pressure-induced phase transitions of N2H4BH3 were investigated using a combination of vibrational spectroscopy, X-ray diffraction, and density functional theory (DFT) up to 30 GPa. Our results showed that N2H4BH3 exhibits remarkable structural stability in a very broad pressure region up to 15 GPa, and then two phase transitions were identified: the first one is from the ambient-pressure Pbcn phase to a Pbca phase near 15 GPa; the second is from the Pbca phase to a Pccn phase near 25 GPa. As revealed by DFT calculations, the unusual stability of N2H4BH3 and the late phase transformations were attributed to the pressure-mediated evolutions of dihydrogen bonding frameworks, the compressibility and the enthalpies of the high-pressure polymorphs. Our findings provide new insight into the structures and bonding properties of N2H4BH3 that are important for hydrogen storage applications.

Effect of hydrogen concentration distribution on flame acceleration and deflagration-to-detonation transition in staggered obstacle-laden channel

A staggered arrangement of solid obstacles promotes flame acceleration (FA) and the deflagration-to-detonation transition (DDT) in a homogeneous concentration field. Many combustible premixed gases, however, are inhomogeneous. The present numerical study explores the effects of different hydrogen–air distributions on the FA and DDT processes in a staggered obstacle-laden channel. The results show that, in the early stage of flame evolution, the flame accelerates faster when there are no obstructions on the side of the channel with the high hydrogen concentration. Under the suction effect of the aperture formed between an obstacle and the wall, the flame experiences multiple periods of velocity augmentation during its evolution. In terms of detonation initiation, the process can be classified as either detonation induced by the interaction between the flame surface and the reflected shock wave from the wall/obstacle, or detonation induced by the collision between the leading shock wave and the reflected shock wave from the obstacle. As the detonation wave propagates, regions with a hydrogen content of less than 12.7 vol. % cause a decoupling of the detonation wave. The morphology of the detonation wave (length, angle, and height) is related to the specific distribution of the hydrogen concentration. From the overall FA and DDT processes, a more homogeneous hydrogen concentration distribution leads to faster flame state variations and a faster triggering of the detonation.

Enhanced NH3 Adsorption Capacity of CuCl2 by Changing the pore structure

Ammonia is an important carrier of hydrogen energy, with the characteristics of high hydrogen content density and no carbon dioxide emission. In recent years, many methods of ammonia synthesis using biomass have been widely studied to improve ammonia yield. Therefore, safe and efficient ammonia capture for ammonia synthesis from biomass is an important way to alleviate the energy crisis and solve the energy problem. In this paper, the NH3 adsorption properties of CuCl2 were measured, and the composite adsorbents were prepared by using silicon and multi-walled carbon nanotubes respectively to support CuCl2, and the NH3 adsorption properties of the composite adsorbents were studied. The study found that the NH3 adsorption capacity of the three adsorbents decreased with the increase in temperature, so metal chlorides were more suitable for the low-temperature adsorption of ammonia. Silicon and multi-walled carbon nanotubes have an enhanced effect on the NH3 adsorption of CuCl2. The reason is that the porous material itself has a physical adsorption effect on ammonia, and silicon can play the role of skeleton support in cupric chloride particles, which enhances the pore structure of the adsorbent, thereby alleviating sintering.

A novel cascade resorption system for high temperature thermochemical energy storage and large temperature lift energy upgradation

The discrepancy between energy supply and demand can be overcome by sorption based thermochemical energy storage system. Thermochemical energy storage system based on metal hydrides is an attractive option due to cyclic stability and high energy storage density. In the present study a novel cascade resorption system is proposed and analyzed for high temperature energy storage. The cascade resorption system uses Mg-50 wt% LaNi5 for energy storage due to its high reaction enthalpy and hydrogen absorption capacity whereas LaNi5 and LaNi4.7Al0.3 are used for hydrogen storage. The temperature at which energy is recovered is increased by two stage cascading desorption method. Therefore, a large magnitude of energy upgradation is possible. An energy upgradation of 52 °C is obtained using the cascade resorption system when the energy source and regeneration temperatures are at 300 and 80 °C, respectively. Thermodynamic analysis shows that the COP and energy storage density of 0.419 and 141.323 kJ/kg, respectively are obtained. In the end, cascade resorption system is compared with the simple resorption system and discussed the relative merits of cascade system. The energy upgradation of 18 and 23 °C is obtained using two simple resorption systems.

Development of Reference Materials for Calibration of the Hydrogen Analyzer at High Concentration

The study discusses the issues of improving the accuracy of measuring high hydrogen concentrations in the development of storage materials in the hydrogen energy industry. The purpose of the study was to develop reference materials for calibration of the hydrogen analyzers at high concentrations. The main methods for determining the hydrogen content in materials were analyzed. It was established that the extraction method in an inert gas medium has found the widest application. The main methods for determining the hydrogen content in materials are analyzed, it is established that the extraction method in an inert gas medium has found the widest application. The need for calibration of analyzers on reference materials with a high hydrogen concentration was noted. Reference materials of titanium alloy VT-1-0 with hydrogen concentration up to (4.0±0.1) wt.% have been developed. The optimal parameters for the analysis were selected. On the example of the hydrogen analyzer RHEN602 (LECO, USA), calibration was carried out on the developed reference materials to obtain a calibration dependence. The reliability of the obtained calibration curve with the application of stoichiometric zirconium hydride was estimated. The confidence interval of the resulting calibration curve was ±10 %. It has been established that the calibration on the developed materials makes it possible to analyze materials with a hydrogen content of 0.5 to 4.0 wt.%. The practical significance of the study lies in the development of reference materials that can be applied to calibrate hydrogen analyzers operating on the principle of melting in an inert gas medium at a high hydrogen concentration.

Experimental study of possibility to increase the efficiency of CO2 utilization on iron-containing fillers with green energy carriers generation

Results of additional laboratory studies are presented for carbon dioxide utilization method with green generation of hydrogen and hydrocarbons. The method consists in interaction of water with dissolved CO2 on the surface of iron-containing fillers. The process proceeds at temperatures starting from ambient conditions and does not require creation of high pressures or electric current in the system. The interaction is accompanied by intense evolution of gas phase with high content of hydrogen. Carbon is transformed into carbonates and small quantities of generated hydrocarbons. Influence of temperature and process parameters is studied for steel turnings used as a prototype of cheap fillers produced from metalworking wastes. The possibility to optimize the degree of CO2 utilization is shown by controlling the carbonized water saturation pressure. According to the results of considered and previous series of experiments, the achieved degree of CO2 utilization is up to 76-83%, with hydrogen content in the output gas of 63-82%. Keywords: carbon dioxide utilization; hydrogen; hydrocarbons; iron-containing filler; carbonated water; iron turnings; green energy carriers.

Biological hydrogen production from paper mill effluent via dark fermentation in a packed bed biofilm reactor

This study assessed the feasibility of continuous hydrogen production in an anaerobic packed bed biofilm reactor (APBR) using paper mill effluent (PME) without any pretreatment or modification. To form a microbial biofilm on supports, the reactor was seeded with a thermal pretreated anaerobic sludge. After the start-up stage, under mesophilic conditions and pH control, the system performance in the case of hydrogen production as biofuel and VFAs as valuable by-products as well as COD removal was investigated at different hydraulic retention times (HRTs) (24, 16, 12, 8, 4, 2 and 1.2 h). The highest hydrogen concentration in the produced gas was 41.5 % obtained at HRT 4 h. The highest hydrogen production rate and yield were 6.21 L H2 d−1 L−1 at HRT 2 h and 0.96 mmol H2 g−1 COD at HRT 8 h, respectively. With decreasing the HRT from 24 to 1.2 h, the OLR was increased from 27.35 to 547 g COD L−1 d−1 that positively affect the hydrogen production rate for all HRTs except for the shortest HRT. Furthermore, COD removal efficiency was reduced from 25.2 to 6 %. Low value of COD removal efficiency is because of conversion of organic inlet to valuable metabolites such as VFAs in the effluent.

Structural, optical and electrical characterizations of Mg/Ti/Ni multilayer thin films deposited by DC magnetron sputtering for hydrogen storage

Magnesium (Mg) based alloys are the most promising hydrogen storage and fuel cell alloys due to their high hydrogen content. In the present work, multilayer thin films (Mg/Ti/Ni) were prepared using direct current (DC) magnetron sputtering method. Multilayered Mg/Ti/Ni thin films were investigated by analyzing the data of different characterizations such as surface, structural, optical and electrical. Uniformity of the deposited thin films was analyzed by Field Emission Scanning Electron Microscope (FE-SEM) and Energy Dispersive Spectrometry (EDS) confirmed the presence of elemental composition. X-ray Diffractometer (XRD) was used to analyze structural characteristics of annealed thin films before and after hydrogenation. The variation in optical absorption and band gap has been observed, with the hydrogenation of thin film and having a larger band gap (3.27 eV) as compared to annealed thin films (2.81 eV). The semiconducting behavior of films is revealed by current voltage (I–V) characteristics of the films, and conductivity reduces after annealing and hydrogenation i.e. from 6.36 to 1.41 kΩ−1cm−1. Furthermore, Hall mobility of annealed without hydrogenated and annealed with hydrogenated thin film was improved (in the order of 103) as compared with as-deposited film. Improvement certainly helps the movement of hydrogen particularly after hydrogenation, the accumulation of hydrogen, particularly at the thin film's interface, obstructs the flow of electrons, resulting in a decrease in thin film conductivity. As a result, multilayer Mg/Ti/NI thin films are the good choice in the consideration for solid state hydrogen storage purpose.

Theoretical and experimental research of hydrogen storage properties of Mg and Mg-Al hydrides

In this work, we studied the effect of aluminum atoms addition on the properties of hydrogen accumulation and desorption in magnesium hydride. Using ab initio calculations and experimental methods, the role of alloying magnesium with aluminum was determined. The hydrogen content in the Mg and Mg–10 at%Al coatings was 1.8 wt% and 4.5 wt%, respectively. For the Mg–10 at%Al coating, the peak temperature of hydrogen desorption was about 425 °C, 17 °C lower than that for the Mg coating. The desorption rate for the Mg coating and Mg–10 at%Al coating was 3 × 10−14 mol(H2)/cm2 s and 31 × 10−14 mol(H2)/cm2 s, respectively. Compared with the Mg coating, the higher hydrogen content in the Mg–10 at%Al coating with the faster hydrogen desorption is related to the energetically more favorable Al-doped Mg system than the pure Mg system with H at the distance from Al at low hydrogen concentrations. The lower hydrogen desorption temperature of the Mg–10 at%Al coating is confirmed to be the consequence of the weakened MgH bond by the doped Al atom due to the higher electronegativity of the Al atom than that of the Mg atom. In addition, the aluminum binding energy decreases more significantly with the hydrogen concentration increase for hydrogen near Al atom than for hydrogen at a distance.

Hydrogen Sensors Based on In2O3 Thin Films with Bimetallic Pt/Pd Catalysts on the Surface and Tin and Dysprosium Impurities in the Bulk

This paper presents the results of studying the characteristics of hydrogen sensors based on thin In2O3 films modified with tin and dysprosium with dispersed double Pt/Pd catalysts deposited on the surface. To control the content of Sn and Dy in the films, an original technology was developed, and ceramic targets were fabricated from powders of the In–Dy–O, Dy–Sn–O, and In–Dy–Sn–O systems synthesized by the sol–gel method. Films of complex composition were obtained by RF magnetron sputtering of the corresponding targets. Structural features of the obtained thin films were studied by Raman spectroscopy. It is shown that various combinations of tin and dysprosium concentrations, as well as the presence of Pt/Pd catalysts on the surface, have a significant effect on the defectiveness of the films and the density of oxygen adsorption centers. As a result, the resistance of sensors in pure air (R0), the activation energies of the temperature dependences of R0, the bending of the energy bands at the grain boundaries of the semiconductor, and the responses to the action of hydrogen in the concentration range of 20–25,000 ppm change. A unique feature of Pt/Pd/ In2O3: Sn (0.5 at%), Dy (4.95 at%) films is their high sensitivity at 20–100 ppm and the absence of signal saturation in the region of high hydrogen concentrations of 5000–25,000 ppm, allowing them to be used to detect H2 in a wide range of concentrations.

Influence of Defects in Graphene-Like Network of Diamond-Like Carbon on Silica Scale Adhesion

Silica scale adhesion onto geothermal power plant equipment reduces the power efficiency. In our previous study, diamond-like carbon (DLC) coatings with low sp2 fractions and high hydrogen contents were found to suppress silica adhesion. Therefore, the present study was aimed at clarifying the mechanism of silica adhesion onto the graphene-like network of DLC. In-lens scanning electron microscopic imaging of silica adhered onto defective graphene indicated that the adhesion occurred on defects in the graphene-like network. First-principles calculations revealed that the graphene with hydrogen-terminated defects exhibited reduced adsorption energy between silica and the graphene-like network. Overall, the simulations and experiments helped establish a silica adhesion model in which defects in the graphene-like network of DLC behave as silica adhesion sites.Graphical

Investigation of Hydrogen Production Performance Using Nanoporous NiCr and NiV Alloys in KBH4 Hydrolysis

Studies of storage and production of hydrogen, which is an alternative to fossil fuels, have been intensified. Hydrogen production from metal borohydrides via catalyst is very attractive because of its advantages, such as controlled production, high hydrogen content, nontoxicity, etc. In this study, the catalytic performances of nanoporous nickel–chromium alloy and nickel–vanadium alloy catalysts prepared with magnetron sputtering in hydrolysis of potassium borohydride, which is a hydrogen storage material, were investigated. Parameters that affected the hydrolysis reaction rate, such as the temperature, the amount of catalyst, and the volume of 0.5 M HCl solution were investigated using response surface methodology. In addition, the prepared catalysts were characterized with XRD and FE-SEM analysis, and the remaining solutions after the reactions were characterized with FE-SEM/EDS analysis. Using response surface methodology, optimum conditions for the maximum hydrogen production rate were determined to be 1.65 g of catalyst, 6% KBH4, 3% NaOH, and 7 mL of 0.5 M HCl at 333 K. Under these conditions, the hydrogen production rates were calculated as 68.9 L·min−1·gcat−1 and 76.5 L·min−1·gcat−1 for NiCr and NiV, respectively.

Effect of the loading mode and temperature on hydrogen embrittlement behavior of 15Cr for steam turbine last stage blade steel

The hydrogen embrittlement of 15Cr martensitic stainless steel, for steam turbine last stage blades, was systematically studied by using slow strain rate tensile (SSRT) test and constant loading tensile (CLT) test at room temperature and 80 °C to simulate the service conditions. It was shown that, despite the lower hydrogen concentration absorbed during SSRT, the hydrogen-induced fracture strength of 15Cr steel for SSRT was lower than the threshold fracture strength for CLT. This was due to the remarkable enhancement in local hydrogen concentration due to the transportation of hydrogen by mobile dislocation during SSRT. In addition, although the higher hydrogen concentration was absorbed during SSRT at 80 °C, the hydrogen embrittlement susceptibility of 15Cr steel for SSRT at 80 °C was lower than that at room temperature, because the degree of local hydrogen accumulation decreased at a higher temperature.

Variation of molecular structures affecting tar yield: A comprehensive analysis on coal ranks and depositional environments

Coal with a tar yield ≥ 7 %, which is measured in the Gray-King assay, is called tar-rich coal in China. However, the comprehensive impact of coal ranks and depositional environments on tar yield is still unclear. Here, the coal petrology, molecular structure, and depositional environment of the samples were thoroughly investigated to clarify the influence of the coal rank and depositional environment on the tar-rich coal. The difference in the tar yield is attributed to the molecular structure. Concerning Fourier transform infrared (FTIR) spectroscopy, the high tar production resulted from the existence of relatively long aliphatic side chains and high aliphatic hydrogen content. For the 13C nuclear magnetic resonance analysis, the structure of the aliphatic carbon also played a crucial role in tar formation. Among these, the various unstable structural parameters (falH/fas, (fas + fap)/fa', fas/fa', falH/fal*) and weak bonds could improve the tar yield. Furthermore, the molecular structures were also controlled by the coal rank. More specifically, the CH2/CH3 in FTIR and the falH, falH/fa*, fas/fa’ in 13C NMR had similar patterns with coal rank, which was close to the pattern between the coal rank and the tar yield. This effect also indicated that the tar yield was mainly influenced by bridge bonds, aliphatic side chains, and branched aromatic carbon. Between similar coal ranks, the molecular structure differences originated from the depositional environment. For the coal facies, the tissue preservation index (TPI) and vegetation index (VI) were negatively correlated with CH2/CH3, Hal/H, and “A factor”. In contrast, they were positively correlated with the oxidation degree (Io2). The gelification index (GI) was also positively correlated with CH2/CH3 and Hal/H. Consequently, the coal-forming environment with a relatively high degree of decomposition, low woody tissue content, and high gelification can form key molecular structures easier, which is beneficial for the tar yield.

Steam gasification of digestate after anaerobic digestion and dark fermentation of lignocellulosic biomass to produce syngas with high hydrogen content

Anaerobic conversion technologies are common for organic waste processing. However, the overaccumulation of digestate remaining after anaerobic conversion of biomass requires consideration of new economically viable ways of its disposal. In this work, the possibility of using steam gasification of digestates after anaerobic digestion (AD) and dark fermentation (DF) of lignocellulosic biomass, in order to obtain syngas with high hydrogen content, was investigated. Several digestates were used as feedstocks: (1) after AD of cow manure and mixture of cow manure and amaranth, and (2) from a dark fermentation (DF) reactor fed with by-products of cereals, bran, sunflower meal and rape cake, and operating at hydraulic retention time of 1 and 2.5 days. A methodology for determining the performance indicators of gasification is presented. The thermochemical conversion temperature was 1000 °C. The main indicators of the gasification process were determined at steam to digestate ratios from 0.45 to 0.65. Syngas obtained by steam gasification of digestates contained up to 62.7% H2 and up to 40.4% CO. The syngas from digestates after DF had high values of the molar ratio of H2 to CO, from 1.9 to 2.3, which makes it promising for conversion to liquid fuel by Fischer-Tropsch synthesis. The lower heating value of the syngas from all digestates was in the range from 12.1 to 12.4 MJ/m3. A combination of biological and thermochemical conversion can be used to generate the maximum amount of hydrogen from agro-industrial waste. This study contributes to the creation of a closed technological cycle for the processing of large-tonnage waste in the agro-industrial complex with the production of high value-added products.

Investigation of Magnetocaloric Properties in the TbCo2-H System

In this work the magnetocaloric effect in the TbCo2-H system in the region of the Curie temperature was studied both by direct and indirect methods in external magnetic fields up to ~1.4 and 14 T, respectively. We have paid special attention to the magnetic and magnetothermal properties of the TbCo2–H with high hydrogen content. The mechanisms responsible for the change in the Curie temperature were established, and the field and temperature dependences of the magnetocaloric effect were analyzed in detail. In addition, the magnetocaloric properties (including critical parameters) for various systems based on the TbCo2 compound were compared. The main regularities of the change in the MCE value and the Curie temperature depending on the composition are discovered and discussed.

On the Origin of the Yellow Luminescence Band in GaN

The yellow luminescence (YL) band with a maximum at 2.2 eV is the dominant defect‐related luminescence in unintentionally doped GaN. The discovery of the mechanism responsible for this luminescence band and related defects in GaN took many years. Eventually, a consensus has been reached that the CN acceptor is the source of the YL band (the YL1 band) in GaN samples grown by several techniques. Previously suggested candidates, such as VGa, VGaON, CNON, and CNSiGa, should be discarded. At the same time, other defects (such as the VN, BeGa, and CaGa) may cause luminescence bands with positions and shapes not much different from the YL1 band. In GaN containing high concentrations of gallium vacancies, oxygen, and hydrogen, complexes containing these species may also contribute in the red–yellow part of the photoluminescence spectrum. The main controversies related to the YL band are resolved.

Structure, Stability, and Electronic Properties of Hydrogenated Monolayer 2D Silicon Allotropes by First‐Principles Calculation

Due to silicon having a sp3 hybridization configuration in nature, most monolayer 2D silicon allotropes have to be proposed based on the dumbbell‐like units to ensure their structural stability. Herein, hydrogenated monolayer 2D silicon allotropes are predicted, and the sp3 configuration of structures is guaranteed by covering the surface with hydrogen. Compared with the corresponding hydrogen‐free structures and the hydrogen‐free structures on Ag(111) substrate, these predicted structures have lower formation energies, indicating that these monolayer 2D silicon allotropes can be obtained by hydrogenation reactions. These predicted structures are all dynamically stable and structures SCH, HPH, and HDH are thermodynamically stable. The structure SLH is the transition‐state structure of structure SCH and structures OTQTH and HHKH are metastable structures. The stable and metastable structures are all semiconductors and can be applied to semiconductor devices. All of these monolayer 2D silicon allotropes have high gravimetric hydrogen contents and may have applications for chemical hydrogen storage or water‐enabled H2 production. It is believed that the results of this work have a good reference value for the experimental synthesis of hydrogenated monolayer 2D silicon allotropes, and have reference significance for understanding the diversity and electronic properties of hydrogenated monolayer 2D silicon allotropes.