High Hydrogen Content Research Articles

Analysis of cyclic thermodynamic system combining ammonia gas turbine and transcritical carbon dioxide

Ammonia has attracted significant research attention due to its high hydrogen content and lack of elemental carbon. Unfortunately, the thermal efficiency of ammonia gas turbines is relatively low. To address this problem, this paper proposes a cyclic system that combines an ammonia gas turbine with the T-CO2 power cycle. The cycle, based on comprehensive energy distribution and utilization, makes full use of the cooling capacity of liquid ammonia fuel to cool CO2 below the critical point and uses the waste heat of the ammonia gas turbine in stages. The paper begins by establishing and validating a thermodynamic model of the combined cycle. Numerical simulations show that, under the basic operating conditions, the energy efficiency of the combined cycle is 53.44%. Next, an analysis of the regenerator of the bottom cycle shows that it introduces a low heat source, which avoids a pinch point in the regenerator. Finally, the study investigates how different key parameters affect the performance of the combined cycle. A calculation indicates that changing the temperature and pressure of the ammonia turbine inlet increases the efficiency of the combined cycle by up to 32.75%. The maximum efficiency of the combined thermal cycle is 62.42%. For a gas turbine inlet pressure not exceeding 5 bar, a small pressure ratio improves the cycle efficiency.

Computational study on single atom anchored on B2C3P monolayer as electrocatalysts for nitrogen reduction reaction

NH3 is an indispensable raw material for the synthesis of life compounds, as well as an intermediate of energy storage materials with high hydrogen content and clean energy carrier. Recently, with the development of electrocatalytic nitrogen reduction reaction (NRR), a new method of green and efficient NH3 synthesis has been found. The key of this method is to design the catalyst with high activity and selectivity. Herein, the catalytic activity of noble metal single atom supported on B2C3P (NM@B2C3P) as electrocatalysts for the NRR was explored by using the first-principles calculation. And the main basis for characterizing the catalyst activity was determined, Ir@B2C3P was successfully screened, which not only have thermodynamic stability, but also exhibit excellent NRR activity with low energy barrier of 0.513 eV and good selectivity. Meanwhile, the analysis of electronic properties also revealed the reason for the high catalytic activity.

Effect of carbon segregation at prior austenite grain boundary on hydrogen-related crack propagation behavior in 3Mn-0.2C martensitic steels

The present study aimed at strengthening prior austenite grain boundary (PAGB) cohesive energy using carbon segregation and investigated the effect of carbon segregation at PAGB on the microscopic crack propagation behavior of hydrogen-related intergranular fractures in high-strength martensitic steels. At the low hydrogen content (below 0.2 wt. ppm), the fracture initiation toughness (JIC) and tearing modulus (TR), corresponding to crack growth resistance, were significantly improved by carbon segregation. In contrast, JIC and TR did not change by carbon segregation at the high hydrogen content (above 0.5 wt. ppm). Considering the non-linear relationship between the toughness properties and the PAGB cohesive energy, the experimentally evaluated toughness properties (JIC and TR) and the GB cohesive energy previously calculated by first-principles calculations were semi-quantitatively consistent even at the high hydrogen content. The microstructure observation confirmed that the plastic deformation associated with crack propagation, such as the local ductile fracture of uncracked ligaments and the formation of dislocation cell structures / nano-voids, played an important role in the non-linear relationship between the toughness properties and PAGB cohesive energy.

Influence of hydrogen ingress and capture on the mechanical properties of spray formed 2195 aluminum alloy

The current research has focused on the hydrogen capturing and its impact on the mechanical properties of spray-formed 2195 (SF2195) aluminum alloy. Microstructure characterization, thermal desorption spectra (TDS) and hydrogen trapping of characteristic microstructure, are used to investigate the generation, migration and trapping of hydrogen. The retention of moisture in the carrier gas is believed to induce high concentration of hydrogen and the amorphous Al2O3 layer within the SF2195 billet, and the local retention of carrier gas brings about pores with the Al2O3 layer on the inner wall. High concentration of hydrogen is captured in the hot-rolled alloy while around 60 % of the hydrogen can be eliminated during the solution-quenching. Particles of T1 phase trap large quantity of hydrogen and the high-density dislocations developed from the pre-stretch promote the migration of hydrogen towards dispersoids and precipitates. The presence of hydrogen and Al2O3 layer contributes to the reduced plasticity of SF2195 alloy. The spreading of flattened pores can induce intensified hydrogen damage effect in local regions and thus contribute to the unusually decreased ductility along the thickness direction in the T8 aged alloy.

The nontrivial effects of annealing on superconducting properties of Nb single crystals

The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 ∘C , 1400 ∘C , and near the melting point of niobium (2477 ∘C ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 ∘C . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 ∘C , measured, annealed at 1700 ∘C , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 ∘C . The clean gap was recovered after annealing at 1700 ∘C . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 ∘C , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from Γ=0.2 to about Γ=0.4 after annealing at 1400 ∘C . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.

The synergistic effect of Cl doping and Bi coupling to promote the carrier separation of BiOBr for efficient photocatalytic nitrogen reduction

Photocatalytic nitrogen reduction reaction (NRR) is a sustainable process for ammonia synthesis under mild conditions. However, photocatalytic NRR activity and are generally limited by inefficient carrier separation and transfer. Therefore, parallel engineering of bulk phase doping and surface coupling is critical to achieving the goal of efficient NRR. In this study, Cl doped BiOBr nanosheet assemblies (BiOBr/Cl) were constructed in delicately designed deep eutectic solvents (DESs), combined with ionothermal methods at low temperatures and Bi3+ exsolution reduction strategy at high temperatures. The unique liquid state and reducibility of DESs induce the reduction of Bi3+ and the in situ coupling of Bi quantum dots at the surface of BiOBr/Cl nanosheets along with the construction of Bi-BiOBr/Cl nanosheet assemblies. The experimental results show that Cl doping could reduce the exciton dissociation energy and promote its dissociation to free carriers. Bi quantum dots could form tightly coupled Schottky junction with BiOBr/Cl enabling the efficient and unidirectional transmission of photogenerated electrons from BiOBr/Cl to metal Bi. The formed electron deficient region at Schottky interface promotes the adsorption and activation of N2. The hierarchical structure of Bi-BiOBr/Cl nanosheet assembly benefits to providing more N2 adsorption active sites. The DFT calculation shows that the accumulation of high concentration of active hydrogen in Bi-BiOBr/Cl leads to a significant decrease of energy barrier of the first step hydrogenation of N2. Bi-BiOBr/Clis more inclined to adsorb nitrogen for NRR in comparison with H* for hydrogen production. The synergistic effect of Cl doping and Bi coupling result in a high NRR activity of Bi-BiOBr/Cl photocatalyst of 6.67 mmol·g−1·h−1, which was 11.3 times higher than that of initial BiOBr. This study provides a promising strategy for designing highly active NRR photocatalysts with high efficiency carrier dissociation and transport.

Hydrogen-rich water alleviates asthma airway inflammation by modulating tryptophan metabolism and activating aryl hydrocarbon receptor via gut microbiota regulation

Hydrogen-rich water (HRW) is a beverage containing a high concentration of hydrogen that has been researched for its antioxidant, anti-apoptotic, and anti-inflammatory properties in asthma. This study investigates the potential therapeutic impact of HRW on the gut-lung axis. Using 16S rRNA and serum metabolomics, we examined changes in gut microbiota and serum metabolites in asthmatic mice after HRW intervention, followed by validation experiments. The findings revealed that HRW influenced gut microbiota by increasing Ligilactobacillus and Bifidobacterium abundance and enhancing the presence of indole-3-acetic acid (IAA), a microbially derived serum metabolite. Both in vivo and in vitro experiments showed that HRW's protective effects against airway inflammation in asthmatic mice may be linked to the gut microbiota, with IAA potentially playing a role in reducing asthmatic airway inflammation through the aryl hydrocarbon receptors (AhR) signaling pathway. In summary, HRW can modify gut microbiota, increase Bifidobacterium abundance, elevate microbial-derived IAA levels, and activate AhR, which could potentially alleviate inflammation in asthma.

Thermal and/or Microwave Treatment: Insight into the Preparation of Titania-Based Materials for CO2 Photoreduction to Green Chemicals.

Titanium dioxide was synthesized via hydrolysis of titanium (IV) isopropoxide using a sol-gel method, under neutral or basic conditions, and heated in the microwave-assisted solvothermal reactor and/or high-temperature furnace. The phase composition of the prepared samples was determined using the X-ray diffraction method. The specific surface area and pore volumes were determined through low-temperature nitrogen adsorption/desorption studies. The photoactivity of the samples was tested through photocatalytic reduction of carbon dioxide. The composition of the gas phase was analyzed using gas chromatography, and hydrogen, carbon oxide, and methane were identified. The influence of pH and heat treatment on the physicochemical properties of titania-based materials during photoreduction of carbon dioxide have been studied. It was found that the photocatalysts prepared in neutral environment were shown to result in a higher content of hydrogen, carbon monoxide, and methane in the gas phase compared to photocatalysts obtained under basic conditions. The highest amounts of hydrogen were detected in the processes using photocatalysts heated in the microwave reactor, and double-heated photocatalysts.

Dynamic Mechanical Analysis of Poly(Vinyl Alcohol)‐Based Gels with Boric Acid as Crosslinker

AbstractGels are soft materials made of a crosslinked polymer network immersed in a fluid. When water is the main component, these materials (hydrogels) find extensive use in the medical and pharmaceutical fields due to the high biocompatibility given by their high water content. The hydrogel ability to absorb water also makes it interesting for radiation shielding applications in space, since a high hydrogen content is helpful to reduce the damage caused by ionizing radiation on astronauts and electronic devices. In this work, crosslinked hydrogels are prepared using poly(vinyl alcohol) (PVA) with boric acid (BA) as crosslinking agent. Results in terms of chemical composition from Fourier transform infrared (FTIR) spectroscopy, mechanical properties from dynamic mechanical analysis (DMA), and swelling behavior are used to assess the BA capacity to form hydrogen and chemical bonds with the PVA macromolecules.

NiO-LaCoO3 catalysts for biomass pyrolysis to hydrogen-rich gas

This study presents a new pathway for effective and environmentally friendly hydrogen generation from biomass pyrolysis using perovskite-type catalysts for highly valuable biomass conversion. Firstly, the impact of different Ni doping levels on LaCoO3 catalytic reactivity was investigated. On this basis, the impacts of different carbide slag adding proportions and reaction temperatures on the hydrogen yield and concentration were investigated. Among them, the maximum hydrogen yield at 600 °C under Ni3La2Co2 catalyst is 553.79 mL/gbiomass when the proportion of carbide slag is 5:15, and the volume concentration of hydrogen is 62.67 vol%. The outcomes demonstrated that the prepared NiO-LaCoO3 has excellent cycling performance, and the hydrogen yield of the Ni3La2Co2 catalyst decreased only marginally from 546.98 mL/gbiomass to 503.94 mL/gbiomass after ten cycles, with a comparatively small reduction of only 7.87 %. In particular, a high hydrogen concentration of 63.43 vol% is maintained in the pyrolysis gas.

Prediction of potential high-temperature superconductivity in ternary Y–Hf–H compounds under high pressure

Compressed ternary alloy superhydrides are currently considered to be the most promising competitors for high-temperature superconducting materials. Here, the stable stoichiometries in the Y–Hf–H ternary system under pressure are comprehensively explored in theory and four fresh phases are predicted: Pmna-YHfH6 and P4/mmm-YHfH7 at 200 GPa, P4/mmm-YHfH8 at 300 GPa and P-6m2-YHfH18 at 400 GPa. The four Y–Hf–H ternary phases are thermodynamically and dynamically stable at corresponding pressure. In addition, structural features, bonding characteristics, electronic properties, and superconductivity of the four ternary Y–Hf–H phases are systematically calculated and discussed. As the hydrogen content and the density of states of H atoms at the Fermi level increase, the superconducting transition temperatures (Tc) of Y–Hf–H system are significantly enhanced. The P-6m2-YHfH18 with high hydrogen content exhibits a high calculated Tc value of 130 K at 400 GPa.

Ternary Fe–Ni–B particles supported on Cu(OH)2–Cu foam: A highly efficient and stable catalyst for hydrolysis of ammonia borane

Ammonia borane (NH3BH3) as a solid chemical hydrogen storage material with a high hydrogen content can be hydrolyzed under mild conditions to release hydrogen. In this work, Fe–Ni–B/Cu(OH)2–Cu foam was synthesized by combining in situ growth and electroless plating. Compared with the binary Fe–B/Cu(OH)2–Cu foam and Ni–B/Cu(OH)2–Cu foam prepared by the same method, the ternary Fe–Ni–B/Cu(OH)2–Cu foam has superior catalytic performance. The Fe–Ni–B/Cu(OH)2–Cu foam catalyst was able to achieve a maximum hydrogen production rate of 5.6 ml min−1 cm−2 at 298 K with an activation energy as low as 46.3 kJ mol−1. And more importantly, its catalytic efficiency has hardly decayed after ten cycles. These excellent properties are due to its low activation energy and the large specific surface, multi–site Cu(OH)2–Cu–foam carrier.

Solid carbonaceous materials transformation during pulverised coal and natural gas co-injection

Co-injection of coal and gaseous fuel, such as natural gas (NG), is common practice promoting pulverised coal gasification in blast furnace (BF) ironmaking. The high hydrogen content in NG makes it possible to act as cleaner reductant to reduce iron ore to produce hot metal, which will result in reduced CO2 emissions during the ironmaking process. In this work, selected parameters affecting the overall performance of the pulverised coal and natural gas co-injection system were studied using the CanmetENERGY injection test rig, including coal injection rate, natural gas rate and blast oxygen enrichment. Increase in combustion intensity promotes conversion of injected coal into solid carbonaceous material with relatively low reactivity with CO2. Hence, it reduces the competitiveness of combustion residues for oxygen in the raceway to continue the gasification process. NG co-injection reduces the coal combustion intensity but enhances the reactivity of combustion residues by competing the oxygen in the raceway.

Role of slip in hydrogen-assisted crack initiation in Ni-based alloy 725.

We conduct in situ tensile straining experiments to investigate the role of hydrogen and slip in crack initiation in nickel-based alloy 725. Our experiments reveal no tendency for hydrogen to enhance localized slip and no necessity of slip for crack initiation. We use electrochemical charging to introduce hydrogen into samples, melt extraction to measure hydrogen content, and digital image correlation to analyze localized plastic strains during in situ tensile tests in a scanning electron microscope. Cracks initiate both in regions with and without nearby localized slip. Moreover, the fraction of cracks initiating with no nearby slip is greater at higher hydrogen content. Slip-assisted crack initiation generally occurs at locations where intergranular slip is arrested, especially at intersections of slipping coherent twin boundaries with thin twin lamellae. Cracks that initiate without nearby slip occur at a wider variety of microstructural features, including inclusions, triple junctions, and surface flaws.

A parametric study on syngas production by adding CO2 and CH4 on steam gasification of biomass system using ASPEN Plus

Abstract Biomass gasification technology is increasingly employed as an environmentally friendly energy source, primarily due to its minimal impact on the environment and its ability to mitigate pollution. This technology excels in producing gas with exceptionally high hydrogen content, making it a valuable source for both fuel and energy carriers. Hydrogen (H2), renowned for its stability and lack of detrimental environmental effects, holds great significance in various applications related to energy utilization and sustainability. In the current work, wood sawdust was utilized as the biomass feedstock for syngas production. The research focused on examining the impact of introducing carbon dioxide (CO2) and methane (CH4) gases into the Gibbs reactors. The steam gasification process was modeled by the ASPEN Plus software, allowing for comprehensive analysis and simulation of the gasification reactions. According to the obtained results, the modeling performed in this study demonstrates good predictive capability when compared to the experimental data. It was shown that when the ratio of CO2 to biomass (C/B) increases, the MFR (mass flow rates) of H2 as well as CH4 decrease, whereas the flow rates of CO2 and carbon monoxide (CO) increase. These findings indicate the influence of the C/B ratio on the distribution of different gases within the gasification process. The reduction in MFR of hydrogen when transitioning from C/B = 0 to C/B = 1 in modes a and b is quantified as 17.51 % and 16.39 %, respectively. These percentages represent the magnitude of the decrease in hydrogen MFR for each specific mode when comparing two carbon dioxide to biomass ratios. When the CH4 to biomass (M/B) ratio increases, the mass flow rates of H2 exhibit a consistent upward trend, while the MFR of CO2 displays a descending form. Specifically, when in the Gibbs reactor, M/B rises from 0 to 1 for modes a and b, the mass flow rates of H2 experience significant increases of 265 % and 243 %, respectively. These findings underscore the direct relationship between the M/B ratio and hydrogen production, highlighting the potential for enhanced hydrogen yields with higher M/B ratios in the studied modes.

Embrittlement of notched duplex stainless steel: Role of hydrogen-assisted void growth and cleavage

The micro-degradation processes related to the ductile-brittle transition are crucial for revealing hydrogen embrittlement mechanisms. This study investigates the evolution and transition of hydrogen-assisted damages in notched duplex stainless steel using a combination of microstructural characterization, numerical simulations, and mechanistic models. The results show that the brittle area of the fracture surface increases rapidly with decreasing cathodic potential, accompanied by the fractography transition in a sequence of voids, voids mixed with quasi-cleavage, and quasi-cleavage. While hydrogen-assisted dislocation emission from the void surface and stress concentration at the phase boundary promote nanovoid growth, hydrogen-enhanced plasticity facilitates preferential void growth along the ferrite block. At higher hydrogen concentrations, ferrite cleavage cracking may originate from prolate voids and hydrogen-augmented Cottrell dislocation reactions, reducing plastic strain near the crack tip and hence diminishing the formation of vacancies as void nuclei. Previous studies have focused on the statistics of hydrogen's effect on void size. This work demonstrates the dislocation mechanism of hydrogen-assisted void growth and provides new insights into the development of micro-mechanism-based models to predict hydrogen embrittlement.

Analysis of the atomic ratio of H and Zr effect on the neutronics parameters of ZrH moderated space nuclear reactor

Zirconium hydride (ZrH) is an ideal moderator for space nuclear reactors due to its exceptional properties, including high hydrogen content, small neutron absorption cross section, and high operating temperature. The primary goal of this study is to examine how the atomic ratio of H to Zr (H/Zr ratio) influences the neutronics parameters of a ZrH moderated space nuclear reactor, with a focus on establishing a reliable reference for ensuring the optimal safety and minimization of such reactors. The neutronics calculation based on the ZrH moderated space nuclear reactor named Topaz-II is performed using the Reactor Monte Carlo code (RMC code) with the ENDF/VII cross-section database. The effects of the H/Zr ratio were studied with a particular focus on the initial keff, the burnup, the temperature reactivity coefficient and the criticality safety. The results show that with the increase of the H/Zr ratio, the initial keff increases while the drums’ worth decreases. The Moderator Temperature Coefficient (MTC) is a positive value that rises as the H/Zr ratio increases. In the dropping accidents, the reactor full of voids with seawater is more serious, and the introduced reactivity decreases with the increase of the H/Zr ratio.

Enhancing safety in hydrogen refuelling stations: Computational analysis of hydrogen explosion hazards

AbstractThis paper aims to enhance the understanding of hydrogen explosions in hydrogen refuelling stations and evaluate associated risk factors using computational fluid dynamics simulations. The model is first validated against the measured data for hydrogen dispersion and explosion. Different scenarios are then modelled to understand the ignition timing and location. The study estimates acceptable distances to minimize asset damage and human injury from explosion incidents. It has been found that higher wind speeds lead to faster and more extensive dispersion of the hydrogen gas released during a leak. In addition, since strong wind can act as a powerful driving force for the shock wave, the impact of the explosion is found to be less. Interestingly, moving the source of ignition to regions with higher hydrogen concentration has a marginal impact on overpressure and temperature; however, the blockage ratio can significantly amplify the overpressure. It is found that cases with high blockage, including storage room, and cases with large volumes of flammable cloud, including leakage from compressor towards the ground, have the highest hazards. The findings will provide valuable insights into fire and explosion prevention in various areas of hydrogen refuelling stations and contribute to safer hydrogen infrastructure construction.

The influence of solid solution hydrogen and precipitated hydride on the creep behavior of Zircaloy-4

The effect of hydrogen on the creep rates of Zircaloy-4 claddings especially in the low hydrogen concentration remains largely unexplored while creep is considered a main mechanism for spent nuclear fuel failure along with hydride-induced mechanisms. Here, we study the influence of hydrogen on the creep behavior of low burnup Zircaloy-4 cladding from a microstructural perspective. The creep tests at 450 °C and 120 MPa reveal that specimens with hydrogen contents below the terminal solid solubility for dissolution (TSSD) at the test temperature exhibited decreased creep resistance as hydrogen concentration increased, while those with hydrogen contents above the TSSD demonstrated increased creep resistance with higher hydrogen concentration. The lowest creep resistance occurs at the hydrogen concentration corresponding to the TSSD. Additional microstructural analyses using electron backscattered diffraction (EBSD) show the increasing intra-granular/inter-granular hydride ratio in the post-crept specimens as the hydrogen concentration decreases, suggesting that hydrogen atoms in solid solution aid creep progression. Also, an increased amount of twin boundaries is observed in post-crept specimens with hydrogen concentration above TSSD. These results suggest that creep assessment in spent nuclear fuels may require caution especially in low-burnup regime.

Effect of functional groups on the adsorption of urea on activated carbon

The recovery of urea, present in the urine of mammals, has the potential of converting a current wastewater pollutant into an energy source due to its high hydrogen content, in alignment with the waste-to-energy principles. Carbon-based materials enable this approach due to their relatively high urea adsorption capacities. This work reveals that the adsorption of urea from aqueous solutions on activated carbon is a combination of weak van der Waals interactions such hydrogen bonds with the aromatic structure of the pristine carbon surface and also with carboxyl groups on the functionalised carbon, showing no appreciable interaction with hydroxyl or lactone groups. The selective introduction and quantification of different oxygen functional groups on activated carbon reveals their independent effect on the urea adsorption capacity, bringing an end to previous discrepancies in the literature. It also demonstrates that the optimisation of carbon materials must balance the increase of carboxyl groups and the decrease of the surface area associated to functionalisation treatments, providing guidance for future developments of carbon-based materials for circular economy applications.