Amount Of Hydrogen Research Articles

Influence of mixed core in the radionuclides releases and hydrogen production for VVER-1000

This paper aims to compare the behaviour of VVER-1000 Nuclear Power Plants (NPPs) under DEC-A/B conditions, contemplating different fuel assemblies considered in mixed cores. The main characteristics of both fuel assemblies are described in this paper, with a focus on highlighting the key differences in mass composition.There are three models under consideration: Model A, Model B and Model C. Model A consists of a core entirely filled with fuel assemblies equipped with grids made of Zr-1 %Nb, referred to as “Type A” through the paper. Model B comprises a core filled with fuel assemblies that have grids made of Alloy 718 (aka Inconel), referred to “Type B”. Lastly, Model C features a mixed core of 151 fuel assemblies with Zr-1 %Nb grids and 12 fuel assemblies with Inconel grids.Initially, the primary distinctions between these fuel assemblies types are the number and composition of their spacer grids. Type A fuel assemblies have 13 grids made of Zirconium, while Type B fuel assemblies have 16 grids made of Inconel. It was initially anticipated that the reduction in the mass of zirconium available for oxidation would lead to lower hydrogen production in Model B compared to Model A. However, it was observed that the Inconel grids in Type B fuel assemblies provide enhanced structural support, prolonging the oxidation reaction and yielding more hydrogen during the initial oxidation phase compared to Type A fuel assemblies.Moving on to the mixed core configuration (Model C), the Inconel grids in Type B fuel assembly also offer superior structural support. This results in an extended oxidation process. The Type A fuel assemblies having a significant zirconium mass, oxidation in intensified, causing a rise in temperature due the exothermic reaction and leading to the producing of a greater amount of hydrogen compared to the other two models. This pattern is also observed in radionuclide releases.In conclusion, this study sheds light on the behaviour of VVER-1000 NPPs under DEC-A/B conditions, considering different fuel assembly types and mixed core configurations. The results indicate that the choice of grid materials significantly influences the oxidation process and hydrogen production, with Inconel grids exhibiting extended oxidation and hydrogen generation behaviour in both pure and mixed core setups.

Effect of Parasitic Gas Evolution Reactions on the All-Vanadium Redox Flow Battery Performance

All-vanadium redox flow batteries (VRFB) as the most promising candidates for large-scale energy storage can overcome the inherent defect of natural energy, such as intermittent and fluctuating, et al. During the operation of VRFB, the parasitic gas evolution reactions (GERs) are unavoidable due to thermodynamic limitation, which yet will cause a series of issues, such as imbalance of state of charge (SOC), graphite electrode degradation, security risk, etc. To have a deeper understanding of the parasitic GERs in VRFB, the present work developed a transient, multidimensional, multiphysics VRFB model coupling the multiphase species transport and electrochemical reactions. The model was validated with in-house experimental data and published literature, which showed great consistency. Following, the temporal-spatial characteristics of GERs and their competition with main cell reactions were analyzed in detail under different charging current densities and electrolyte flowrate. The results showed that the rate of hydrogen evolution reaction (HER) at the negative electrode is several magnitudes higher than that of the oxygen evolution reaction (OER) at the positive electrode. Besides, the HER happens during the whole charge-discharge process since the activation overpotential remains negative while the OER occurs only at the end of the charging process under high charging current density. It is notable that the HER mainly occurs in the region near the bipolar plate and increases with increasing charging current density. Since HER is favored thermodynamically over the reduction reaction of trivalent vanadium ions, the activation overpotential of the HER remains much higher than that of the main cell reaction during the whole charge-discharge process, albeit the volumetric current density for hydrogen evolution accounts for only part of the overall current due to the limitation of the reaction kinetics. The HER increases with the SOC and causes a SOC imbalance of 0.54% within 10 charge-discharge cycles, thereby accounting for an 11.0% degradation in the VRFB’s capacity. A high current density decreases the amount of hydrogen generated during a charge-discharge cycle yet also causes hydrogen accumulation in the porous electrode due to faster hydrogen generation. The present work takes a comprehensive and detailed discussion about the characteristics of parasitic gas evolution reactions and their effect on the VRFB performance, which gives a deeper understanding of the energy loss mechanism of VRFB for its development and optimization. Figure 1

(Digital Presentation) Designing New Complex Hydrides Based on Transition Metals for Hydrogen Storage Applications

The widespread implementation of the hydrogen economy demands access to materials with a high weight percentage of hydrogen. Mg-based hydrogen storage alloys have become a research hot-spot in recent years owing to their high hydrogen storage capacity, good reversibility of hydrogen absorption/desorption, low cost, and abundant resources. However, high decomposition temperature of Mg-based hydrideslimits their practical usage. Hydrogen is lightest of all elements, typically it need large volumes or high pressures to store appreciable amount of hydrogen.To overcome these challenges research activities are currently going on metal hydrides and complex hydrides based on transition metal. The main challenges come when endothermic decomposition enthalpy is considered. It becomes difficult to release the hydrogen at ambient thermodynamic conditions. On the other hand, the meta-stable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favourable under the ambient conditions. The good kinetics along with evolution of hydrogen around the room temperature possessed by these materials offer much promise for underground storage and it can be used as a grid energy.The present research specifically focus on transition metal based complex hydrides such as NaMgMnH6 and NaMgFeH6 for hydrogen storage and especially predicted the crystal structure of the same using VASP simulation package. ABCX6 and AB2X6 were taken as reference composition A,B,C and X were substituted with Na, Mg, transition metals(Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) and H, respectively.From the ICSD database search the corresponding structural variants were considered as trial structure to predict the ground state structure of these newly designed compounds. using the predicted ground state structure for these compounds, important properties like formation energy, hydrogen site energy, partial density of states(pDOS), electron density(ED), Mulliken effective charge(MEC), Bader electron charge(BEC), Born effective charge, ELF and COHP were calculated. the calculated properties of these compounds were compared with the well known reference compounds. We found that both NaMgMnH6 and NaMgFeH6 are stable with negative formation energy and als othey are semiconductors with the band gap value of 0.51eV and 1.01 eV, respectively. from the calculated electronic structure we found that both these materials are having indirect band behaviour. Analysing the electronic density of states, charge density and various charges mentioned above the chemical bonding behaviour was established as iono-covalent in nature. from the force as well as stress minimisation considering 53 structural variants as input the ground state structure, its space group, equilibrium lattice parameters and atom positions are listed. Also from the energy vs. volume curve for the ground state structure, the equilibrium volume, bulk modulus and pressure derivatives were found out. Among NaMgMnH6 and NaMgFeH6 our spin polarised calculation show that NaMgMnH6 is possesing spontaneous magnetic polarisation with substantial magnetic moment at the Mn site. Among the considered paramagnetic, ferromagnetic, as well as A-, C-,and G- antiferromagnetic configurations the G type antiferromagnetic configuration is found to be the ground state for NaMgMnH6.

In Situ Measurement of Hydrogen Absorption into Copper-Coated Titanium Using Neutron Reflectometry and Electrochemical Impedance Spectroscopy

We set out to investigate the possibility that a small amount of hydrogen, generated by sulfide-driven corrosion or radiolytic processes, might be absorbed into the copper coating proposed for use as corrosion protection for the used nuclear fuel containers (UFCs) to be stored in a deep geological repository (DGR) in Canada. Hydrogen absorption may have the potential to alter the mechanical properties of the copper coating. This contribution discusses our initial study, using in situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS), of hydrogen absorption into a 50-nm layer of copper coated onto 4 nm of Ti on a Si single-crystal substrate. In situ NR-EIS experiments detected no increase in the hydrogen content within the copper layer of the copper-titanium thin film following 55 h of polarization in deoxygenated 0.1 M NaCl solution at pH 9, at potentials ranging from −444 mV/SCE to −1300 mV/SCE (detection limit ~2 at.%). However, these NR results showed that hydrogen can be absorbed into copper when the latter is cathodically polarized below about ─900 mV/SCE, which is the experimentally measured potential threshold for the hydrogen evolution reaction (HER) under these conditions. Although hydrogen did not accumulate in the outer Cu layer, our experiments revealed that the absorbed hydrogen quickly traversed the Cu layer to concentrate in the underlying titanium layer, which favours absorbed hydrogen. This observation is consistent with hydrogen uptake measured using inert gas fusion analysis on oxygen-free, phosphorus-doped (OFP) copper, which showed that in the absence of hydrogen recombination inhibitors (e.g., As(III)), only a small increase of 22 wt. ppm hydrogen was absorbed into the copper after 24 h at E = −1300 mV/SCE, and no increase in absorbed hydrogen occurred at potentials of −1100 mV/SCE or more positive. The initial absorption efficiency for electrolytically produced hydrogen atoms at the copper surface was determined to be 3.2%, suggesting that there may be an upper limit for hydrogen uptake by the copper coating of the UFC, although studies on 3 mm copper-coated steel samples representative of UFC materials will be required to confirm that. This result supports the prediction that hydrogen absorption is unlikely to lead to any failure of the copper barrier within a proposed DGR, in which it will not be possible to achieve such negative electrochemical potentials. Intended future research using in situ NR-EIS to study hydrogen absorption during the corrosion of copper thin films by HS⁻ ions and further studies on hydrogen absorption into 3-mm-thick copper-coated steel samples will help to validate these conclusions.

Hydrogenation of silicon-nanocrystals-embedded silicon oxide passivating contacts

We investigate the effect of hydrogen passivation of dangling bonds in silicon oxide passivating contacts with embedded silicon nanocrystals (NAnocrystalline Transport path in Ultra-thin dielectrics for REinforced passivation contact, NATURE contact). We first investigated the differences in electrical properties of the samples after hydrogen gas annealing and hydrogen plasma treatment (HPT). The results show that the NATURE contact was efficiently passivated by hydrogen after HPT owing to the introduction of hydrogen radicals into the structure. Furthermore, we examined the dependence of process parameters such as HPT temperature, duration, and H2 pressure, on the electrical properties and hydrogen depth profiles. As a result, HPT at 500 °C, 15 min, and 0.5 Torr resulted in a large amount of hydrogen inside the NATURE contact and the highest implied open-circuit voltage of 724 mV. Contact resistivity and surface roughness hardly increased when HPT was performed under the optimized condition, which only improved the passivation performance without deteriorating the electron transport properties of the NATURE contact.

The thermal model and vertical trajectory prediction of the high-altitude float of double-layer latex balloon

The traditional single-layer latex balloon (SLB) is difficult to float at high altitude. To improve the level of meteorological observation, a new and easy-to-implement double-layer latex balloon (DLB) system was proposed to solve the high-altitude floating problem in this work. The amount of hydrogen is critical for the DLB system, but it is difficult to control precisely. Therefore, a thermal model of this balloon structure was developed for calculating the heat source during the ascent and floating phase of the DLB system. The geometric, atmospheric, and dynamic model of the DLB structure was also developed so that its vertical trajectory could be predicted. We combined the actual experimental data to verify the accuracy of the prediction algorithm, and the results showed that the thermal model and vertical trajectory algorithm can meet the needs of practical applications. The temperature calculation data in the balloon is consistent with the experimental data. The predicted vertical trajectory is consistent with the experimental data, and the prediction accuracy of the floating height is 98.4 %. Finally, a software specifically for calculating the hydrogen quantity and predicting the vertical trajectory of the DLB system was developed for engineering guidance.

Evaluation of hardwood or softwood bark biomass as feed materials for aqueous-phase reforming gasification process

In the present study, pine (Pinus brutia) and poplar (Populus alba) tree barks, softwood and hardwood representative biomass were evaluated for production of gas biofuel, hydrogen by aqueous-phase reforming. The proximate composition, elemental composition, higher heating values (HHVs), proximate thermogravimetric and differential thermogravimetric analysis (TGA/DTG), fourier transform infrared (FT-IR), and volatile composition of these biomass materials were determined and their effect on gasification performance of the softwood and hardwood biomass were evaluated. Gasification was performed by aqueous-phase reforming of solubilized liquid fraction of the biomass materials in presence of carbon-supported Pd catalyst which was synthesized in the present study. Softwood contained significantly higher levels of ash and volatile matter, with lower hemicellulose but higher lignin content. Gasification results showed that softwood produced slightly higher amounts of hydrogen with significantly lower carbon monoxide compared to hardwood. Although solid hardwood bark composition was expected to produce more gaseous products, the results observed were opposite. The dissolution of biomass in pressured hot water prior to gasification resulted in a more dilute hydrolysate in softwood compared to hardwood, positively influencing the gasification performance. Despite of many advantages of the aqueous-phase reforming (APR) gasification process used in the present study, the process still needs to be improved further to make the process more economical. To increase the advantage of this process, new catalysts that are more robust and active and have high stability in organic-rich APR conditions should be developed.

Effect of expanded natural graphite addition and copper coating on reaction kinetics and hydrogen storage characteristics of metal hydride reactors

Experimental and numerical studies are carried out to determine the effects of copper coating and/or ENG (expanded natural graphite) addition on the hydrogen storage performance of ground LaNi5. The amounts of copper coating and/or ENG addition are also investigated. The results reveal that the thermal conductivity of ground LaNi5 can be improved by up to ∼6 and ∼12 times with copper coating and ENG addition, respectively. This results in enhanced hydrogen absorption kinetics thereby significantly reduced hydrogen charging times, compared to those determined for LaNi5 without any addition. On the other hand, the amount of hydrogen stored shows a decreasing trend with increasing copper coating and ENG addition since the weight of storage material loaded to the reactor is kept the same. Nevertheless, the optimum copper and ENG contents are determined regarding the amount of stored hydrogen and the corresponding charging time. Similar H/M values are obtained with the optimized powders with additives compared to that of ground LaNi5. Based on these results, various new samples are also prepared by mixing the decided copper coated LaNi5 and ENG added LaNi5 powders and examined to optimize the composition of these blended powders.

Hydrogen enhanced localized plasticity in zirconium as observed by digital image correlation

Hydrogen embrittlement in zirconium alloys is a highly relevant research topic, important for ensuring the integrity of nuclear fuel clads. While the presence of hydrides in zirconium-based clad is a well-known risk factor due to their brittleness, the effect of the presence of hydrogen in solid solution is unclear.According to the Hydrogen Enhanced Localized Plasticity (HELP) model, hydrogen in solid solution may affect the mechanical performance of a metal by increasing dislocation mobility due to the shielding effect that hydrogen has on the interaction of dislocations with other types of defects. In the presented work, the presence of HELP has been assessed in Zircaloy-4 samples, under conditions relevant to the storage of spent nuclear fuel.Elevated temperature tensile tests were performed on samples containing localized areas of higher hydrogen concentration, as quantified by neutron radiography. Digital Image Correlation (DIC) analysis was performed on the specimen surfaces for quantitative characterization of strain heterogeneity during deformation to identify the regions where the plastic strain localization occurs.These regions could be correlated to elevated amounts of hydrogen in solid solution, that is, in the location immediately adjacent to dissolving hydrides, or in the areas of the samples with local hydrogen concentration close to the expected terminal solid solubility limit (TSS) in the test conditions.The results confirm the presence of localized softening caused by solid solution hydrogen, indicating that the HELP mechanism needs to be taken into account when modeling the mechanical response of zirconium-based nuclear fuel clads at elevated temperatures.

The Ammonia Combustion Engine for Future Power Generation Applications

Energy storage is one of the big challenges for the energy transition and ammonia as a hydrogen carrier is considered a promising candidate for efficient and medium‐ to long‐term chemical storage. Gas engines are well suited for power generation using ammonia as a carbon‐free fuel, making it unnecessary to convert ammonia back to hydrogen for the utilization in the power plant. This study investigates operating strategies for a prechamber combustion concept for a large‐bore gas engine suitable for power generation applications. To overcome the high ignition energy and low laminar flame speed of ammonia, different quantities of hydrogen as a promoting agent to improve the combustion properties of ammonia have been employed in the experimental investigations on a single‐cylinder research engine. The combustion concept shows a wide operating range with stable and robust combustion from 0.3 to 2.5 MPa indicated mean effective pressure and will be transferred to a multicylinder engine for the first combined heat and power demonstration.

Microstructure and gas-solid hydrogen storage properties of La1-xCexY2Ni10.95Mn0.45 (x = 0 – 0.75) alloys

RE-Y-Ni-based superlattice alloys have been studied for their high hydrogen storage capacity and excellent activation properties. However, their practical applications in gas-solid hydrogen storage devices are limited by their low hydrogen absorption/desorption platform pressure and the occurrence of a double platform phenomenon. In this study, we investigated the phase structure and gas-solid hydrogen storage properties of La1−xCexY2Ni10.95Mn0.45 (x = 0, 0.15, 0.30, 0.45, 0.60, 0.75) alloys. As the Ce content increases, the content of Ce2Ni7 phase and the platform pressure also increase, while the hydrogen storage capacity and hydrogen desorption enthalpy decrease. When the Ce content increases to 0.45, the Gd2Co7 phase disappears and the LaNi5 phase appears, the hydrogen absorption/desorption platform of the alloy changes from a double platform to a single platform. However, the increase in Ce content leads to a higher amount of residual hydrogen during the dehydrogenation process, attributed to the increased content of the Ce2Ni7 phase. The La0.55Ce0.45Y2Ni10.95Mn0.45 alloy exhibits a hydrogen absorption capacity of 1.61 wt%, with a capacity retention of 97.89% after 100 cycles, and achieves a hydrogen desorption platform pressure of 0.23 MPa. These results indicate that this alloy demonstrates the best overall hydrogen storage performance, characterized by high platform pressure and hydrogen storage capacity.

Design, modeling, and analysis of a PV/T and PEM fuel cell based hybrid energy system for an off-grid house

Net-zero emission targets have imposed the transition to clean and efficient energy technologies, considering the problems arising from the discontinuous and variable nature of renewable energy resources. Integrated energy systems based on solar and hydrogen energy are becoming essential to obtain uninterrupted power, especially for off-grid applications. This study focuses on the design, modeling, and evaluation of such a system that meets the energy consumption of a residence in Türkiye. The framework basically consists of photovoltaic/thermal panels (PV/Ts), batteries, a PEM electrolyzer (PEM-El), hydrogen (H2) storage tanks, and PEM fuel cells (PEM-FC). A zero-dimensional mathematical model was developed for each of the components of the system. Yearly analyses were conducted with a new control strategy based on power balancing, and dynamic variations in power generated by the PV/T panel, the SOCs of batteries, the power consumption of the PEM-El, the power generated by the PEM-FC and the amount of hydrogen in the tank were examined. The results showed that the electricity requirement of a 100 m2 house can be met continuously for a year with 20 PV/T panels (total area of 32.71 m2) with a total capacity of 62 kW, 8 batteries with a total capacity of 192 kWh, and 7 H2 storage tanks with a total capacity of 29.4 kg. It was also shown that the electricity needs of the house is met by stored hydrogen between December and April. Furthermore, the hybrid system’s economic evaluation was carried out and the investment cost of the system was calculated.

Research on design and multi-frequency scheduling optimization method for flexible green ammonia system

As an important chemical product and energy carrier, green ammonia is a way to consume large quantities of green hydrogen produced from renewable electricity. For the optimization of the green ammonia production systems, a primary problem is to solve the electricity-hydrogen-ammonia matching problem under multi-frequency and multi-amplitude load fluctuations. In this work, a method for capacity designing and scheduling optimization of a hybrid multi-frequency flexible green ammonia system is constructed. The method can be applied to design the whole green ammonia system in grid-connected and isolated scenarios. The established model can accurately describe the electricity-hydrogen-ammonia matching characteristics of each module. Furthermore, many important practical engineering constraints are taken into account, such as the operating time of the chemical device, and the flexibility of the ammonia device. This work verifies the effectiveness of the proposed method based on a real case, and the impact of load range, adjustment speed, and adjustment frequency of the ammonia synthesis process on the product cost and module capacity.

Efficient enhancement of photothermal conversion of polymer-coated phase change materials based on reduced graphene oxide and polyethylene glycol

Reduced graphene oxide (rGO) aerogel is frequently employed in support phase change material (PCM) and function as heat conductors in phasing-energy storage systems, absorbing and converting solar energy. However, their low filler content and insufficient reduction have caused a far inferior photothermal performance than graphene. Therefore, it is urgent to enhance light-heat conversion efficiency of rGO-based composite PCM. Herein, a photothermal coating material, polydopamine (PDA), has been selected as a coating for rGO aerogel to further increase the photothermal conversion efficiency of rGO-based composite PCM by conjugation effect. First, rGO aerogel is created by hydrothermal reduction and freeze-drying techniques, followed by dopamine self-polymerization on the rGO surface to form PDA-coated rGO (rGO-PDA) aerogel, and finally composite PCM (PEG (Polyethylene glycol) /rGO-PDA) are prepared by vacuum impregnation technique. The results indicate that PDA exhibits excellent photothermal conversion ability, increasing the absorption of PEG/rGO-PDA in the infrared band, thus resulting in the composite PCM exhibiting excellent photothermal conversion efficiency (88.9 %), which is 2.4 % higher compared to that of PEG/rGO. Furthermore, PDA has strong hydrophilicity, which enhances the affinity between rGO aerogel and PEG, and the large amount of hydrogen bonding provided by the addition of PDA contributes to maintain the morphology stability of composite PCM. The composite PCM with better form-stable and higher photothermal conversion efficiency could play a critical role in solar energy storage system.

Experimental and CFD analysis on the impact of hydrogen as fuel on the behavior of a passenger car gasoline direct injection engine

The influence of hydrogen induction on the behavior of a Multi cylinder automotive GDI (Gasoline Direct Injection) engine was studied. An advanced 3D engine simulation was done and validated with experimentally acquired 5% and 10% hydrogen mass coupled with gasoline direct injection. Comparing to the pure gasoline mode, introducing hydrogen showed considerable improvement in engine's BTE (brake thermal efficiency) at all power outputs. The maximum BTE was observed as 27.2%, 30% and 32.5 respectively with pure gasoline, 5% and 10% hydrogen mass shares at the engine's power output of 21 kW. At all power outputs, hydrogen admission was shown to produce a smaller amount hydrocarbon (HC) and carbon monoxide (CO) emissions than pure gasoline operation. At 21 kW engine power the HC was noted as 3360, 2400 and 2050 ppm respectively with Pure Gasoline, 5% and 10% hydrogen mass shares. CFD results on the HC and CO emissions indicated a strong agreement with the experimental results. NOx emission was noted as higher with hydrogen addition (80 and 100 ppm respectively with 5% and 10% hydrogen mass shares) as compared to 60 ppm with pure gasoline mode. High temperature of the gas supported by the CFD due to the rapid combustion of hydrogen was noted as the reason for the higher NOx emissions with hydrogen addition. CFD results on cylinder pressure and HRR matched very well with the experimental results. A small amount of hydrogen added to the gasoline as a fuel supplement might greatly improve BTE while lowering HC and CO emissions. The recommended optimum hydrogen mass share is 10% for the best performance of the above said engine without any modification in engine design.

EVALUATION OF THE PERFORMANCE OF POLYMER ELECTROLYTE MEMBRANE FUEL CELL (PEMFC) DESIGNED IN DIFFERENT SIZES

Fuel cells, which are the technology of the future, are the formation of electrical energy by the combination of hydrogen and oxygen as a result of a chemical reaction and the release of heat with H2O as waste. The fuel cell is a device that consists of an electrolyte and two electrodes during this coupling and converts chemical energy into electrical energy. Since electricity is produced without combustion, less pollution occurs. The part where the chemical reaction takes place in the Polymer Electrolyte Membrane (PEM) fuel cell consists of the membrane. In this study, the fuel consumption of different sizes (5-25-50 cm2) of fuel cells was investigated and the factors affecting the performance were determined experimentally. First of all, the PEM fuel cell was installed, and appropriate amounts of Hydrogen (H2) and Oxygen (O2) were sent to the fuel cell according to the characteristics of the established cell. During the study, the performances of different sizes of fuel cells were determined. The performance of fuel cells was evaluated according to their size and the amount of electrical energy they would produce was calculated. It was determined that the most efficient fuel cell is C60H60 with a size of 5 cm2, C60H46 with a size of 25 cm2 and C60H46 with a size of 50 cm2.

Effects of cellulose contamination on polystyrene recycling to styrene monomer via microwave pyrolysis

The increasing population and by extension the plastic waste increasing rate requires innovative waste management mitigation solutions, especially for a challenging polymer such as polystyrene. However, the presence of a broad range of contaminants in its waste stream, cellulose-based contaminants being one of the most prevalent, hinders polystyrene recycling. Herein, a microwave co-pyrolysis of polystyrene and cellulose was carried out to recycle styrene as monomer and to investigate the synergy between both reactants at 500°C. Polystyrene pyrolysis presented a high styrene yield of 0.355g styrene/g polystyrene; while as the cellulose content increased, higher amounts of hydrogen are produced, leading to the hydrogenation of styrene into ethylbenzene and other styrenic derivatives such as 1,4-Diphenyl-2-butene and 1,3-Diphenyl-1-butene. A noticeable 29% decrease in styrene yield was observed for an equal amount of polystyrene and cellulose. At the same conditions, the detrimental effect of the co-pyrolysis also involved the reduction of the oil yield, from 58.9%, polystyrene pyrolysis, to 30.2%. The negative synergy between cellulose and polystyrene co-pyrolysis for the recycling of styrene monomer indicates that polystyrene waste streams must be handled thoroughly prior to being recycled.

Few‐Hydrogen Metal‐Bonded Perovskite Superconductor MgHCu3 with a Critical Temperature of 42 K under Atmospheric Pressure

AbstractSince the prediction of multi‐hydrogen high‐temperature superconductor by Ashcroft in 2004, many possible candidates have been proposed, e.g., LaH10 showing the highest superconducting transition temperature (Tc) around 250–260 K at 170‐200 GPa hitherto. However, this pressure is too large to be taken into practical use. To address this challenge, it proposes a few‐hydrogen metal‐bonded perovskite superconductor, MgHCu3, by combining a novel design idea with first‐principles calculations. Different from multi‐hydrogen hydrides, whose high Tc relies on extreme pressure, the metallic bond in few‐hydrogen superconductor MgHCu3 improves the structural stability and ductility at atmospheric pressure. Here, the small amount of hydrogen is found to be vital for Tc. After the incorporation of hydrogen, the electron–phonon coupling constant of MgHCu3 is increased to 0.83, which is larger than that of the well‐known MgB2. Moreover, the anisotropy of MgHCu3 also plays an important role in enhancing Tc. Based on the Migdal‐Eliashberg theory, it predicts that the phonon‐mediated metal‐bonded perovskite MgHCu3 is a superconductor with Tc of 42 K. The first predicted ternary metal‐bonded perovskite, MgHCu3, enriches the family of perovskite and will promote further investigation on few‐hydrogen superconductors under atmospheric pressure.

Surface chemical composition of single WNh stars

Context. Wolf–Rayet (WR) stars of the WNh category contain a significant fraction of hydrogen at their surface. They can be hydrogen-burning, very massive stars or stars in a post-main sequence phase of evolution. Also, WNh stars are sometimes not included in population synthesis models. Aims. We aim to better characterise the properties of single WNh stars in the Galaxy and the Magellanic Clouds. In particular, we want to constrain their surface chemistry beyond the hydrogen content by determining the helium, carbon, and nitrogen surface abundances. Methods. We perform a spectroscopic analysis of 22 single WNh stars. We fit their ultraviolet and/or optical spectra using synthetic spectra computed with the code CMFGEN. We determine the main stellar parameters (temperature, luminosity, mass-loss rates) and the surface H, He, C, and N mass fractions. We investigate the ability of current evolutionary models to reproduce all parameters at the same time. Results. We find that all WNh stars show the signatures of CNO-cycle material at their surface: they are carbon-depleted and nitrogen-rich. A clear trend of higher nitrogen content at higher metallicity is observed, as expected. The amount of hydrogen (X) varies significantly from one star to another, independently of luminosity. Values of X larger than 0.4 are not exceptional. The majority of Galactic WNh stars can be explained by evolutionary models, provided sufficient fine-tuning of the input parameters of evolutionary calculations. At lower metallicity, most stars escape predictions from evolutionary models. This has been noted in the literature but constraints on the surface nitrogen content exacerbate this severe issue. Conclusions. Our study highlights the need to refine the treatment of WR stars in both stellar evolution and population synthesis models.

Preliminary analysis of refilling cold-adsorbed hydrogen tanks

The effective storage of hydrogen is a critical challenge that needs to be overcome for it to become a widely used and clean energy source. Various methods exist for storing hydrogen, including compression at high pressures, liquefaction through extreme cooling (i.e. -253 °C), and storage with chemical compounds. Each method has its own advantages and disadvantages. MAST3RBoost (Maturing the Production Standards of Ultraporous Structures for High Density Hydrogen Storage Bank Operating on Swinging Temperatures and Low Compression) is a European funded Project aiming to establish a reliable benchmark for cold-adsorbed H2 storage (CAH2) at low compression levels (100 bar or below). This is achieved through the development of advanced ultraporous materials suitable for mobility applications, such as hydrogen-powered vehicles used in road, railway, air, and water transportation. The MAST3RBoost Project utilizes cutting-edge materials, including Activated Carbons (ACs) and high-density MOFs (Metal-organic Frameworks), which are enhanced by Machine Learning techniques. By harnessing these materials, the project seeks to create a groundbreaking path towards meeting industry goals. The project aims to develop the world’s first adsorption-based demonstrator at a significant kg-scale. To support the design of the storage tank, the project employs Computational Fluid Dynamics (CFD) software, which allows for numerical investigations. In this paper, a preliminary analysis of the tank refilling process is presented, with a focus on the impact of the effect of the tank and hydrogen temperatures on quantity of hydrogen adsorbed.