Hydrogen Solubility Research Articles

Effects of Cr, Mn, and Fe on the hydrogen solubility of Ni in high-pressure hydrogen environments and their electronic origins: An experimental and first-principles study

Effect of the addition of Cr, Mn, or Fe to Ni on the material's hydrogen solubility are investigated to establish guidelines for designing materials authorized to use in high-pressure hydrogen environments. The exposure to 100 MPa hydrogen gas at 160 °C reveals that the addition of 30 wt%Fe to Ni decreases the hydrogen solubility by 40%, while the addition of 20 wt%Cr to Ni increases it by 65%. Surprisingly, incorporating 20 wt%Mn causes a remarkable increase of 992%. By employing a combined approach of a random alloy model based on the special quasi-random structure and first-principles calculations, we are able to semi-quantitatively predict the effects of these alloying elements on hydrogen solubility. Moreover, the deconvolution of hydrogen bonding energy into its volumetric, mechanical, and chemical components clarifies that the significant impact of Mn is primarily attributed to a substantial expansion of the lattice constant.

The SPIZWURZ project – Experimental investigations and modeling of the behavior of hydrogen in zirconium alloys under long-term dry storage conditions

In order to investigate the occurring processes during long-term dry storage of spent fuel assemblies, a joined project called SPIZWURZ, between the Karlsruhe Institute of Technology and the Gesellschaft für Anlagen-und Reaktorsicherheit (GRS), was started. Aim of the SPIZWURZ project is the determination and quantification of the influence of texture and elastic strain on diffusion and solubility of hydrogen in three different zirconium alloys used in western Europe during a long-term cooling transient (1 K/d) starting at 400 °C. The strain in the cladding of an irradiated spent fuel rod shall be measured. Models predicting the formation of radial oriented hydrides will be validated, improved, and implemented in the GRS fuel rod performance code TESPA-ROD. This paper describes the SPIZWURZ project and already obtained first results.

Phase Equilibria, Solidified Microstructure, and Hydrogen Transport Behaviour in the V-Ti-Co System.

At present, the V-Ti-Co phase diagram is not established, which seriously hinders the subsequent development of this potential hydrogen permeation alloy system. To this end, this article constructed the first phase diagram of the V-Ti-Co system by using the CALculation of PHAse Diagrams (CALPHAD) approach as well as relevant validation experiments. On this basis, hydrogen-permeable VxTi50Co50-x (x = 17.5, 20.5, …, 32.5) alloys were designed, and their microstructure characteristics and hydrogen transport behaviour were further studied by XRD, SEM, EDS, and so on. It was found that six ternary invariant reactions are located in the liquidus projection, and the phase diagram is divided into eight phase regions by their connecting lines. Among them, some alloys in the TiCo phase region were proven to be promising candidate materials for hydrogen permeation. Typically, VxTi50Co50-x (x = 17.5-23.5) alloys, which consist of the primary TiCo and the eutectic {bcc-(V, Ti) and TiCo} structure, show a high hydrogen permeability without hydrogen embrittlement. In particular, V23.5Ti50Co26.5 exhibit the highest permeability of 4.05 × 10-8 mol H2 m-1s-1Pa-0.5, which is the highest value known heretofore in the V-Ti-Co system. The high permeability of these alloys is due in large part to the simultaneous increment of hydrogen solubility and diffusivity, and is closely related to the composition of hydrogen permeable alloys, especially the Ti content in the (V, Ti) phase. The permeability of this alloy system is much higher than those of Nb-TiCo and/or Nb-TiNi alloys.

Local Hydrogen Measurements in Multi-Phase Steel C60E by Means of Electrochemical Microcapillary Cell Technique

By utilizing hydrogen as an eco-friendly energy source, many metals are exposed to gaseous (pressurized) hydrogen. High-strength steels with an ultimate tensile strength of 800 MPa and above are especially susceptible to hydrogen-induced fracturing, also referred to as hydrogen embrittlement (HE). Both the microstructure and phase fractions within the steel, as well as lattice distortion, carbide precipitation, residual stress, etc., significantly affect the susceptibility to HE. Among others, one important cause for this observation is found in the locally varying hydrogen solubility within different microstructural phases such as martensite, bainite, pearlite, and ferrite. Both a thorough understanding of the HE mechanisms and taking countermeasures in the form of alloying design require an accurate analysis of local diffusive hydrogen concentrations within the material. Thermal analysis methods such as Thermal Desorption Mass Spectrometry only display an integral hydrogen concentration throughout the whole sample volume. To analyze the local diffusive hydrogen concentration, novel measuring techniques with a high special resolution must therefore be utilized. The current research presents first-of-its-kind hydrogen analyses by means of the electrochemical microcapillary cell. Using a 10 µm tip opening diameter allows for conducting local diffusive hydrogen measurements within individual grains of multi-phase carbon steel C60E (1.1221). The results confirm that hydrogen is distributed heterogeneously within multi-phase steels. Considering the individual phase fractions and the respective local diffusive hydrogen concentrations, a total diffusive hydrogen concentration can be calculated. The obtained value is in good agreement with reference thermal hydrogen analyses. Our results suggest that electrochemical microcapillary cell measurements offer great potential for further studies, which will provide a better understanding of HE and local hydrogen accumulation.

Effect of Mo alloying on vacancy-defect evolution and irradiation damage in titanium alloy

The evolution of defects and irradiation damage in Ti and Ti-Mo alloy under hydrogen ion irradiation were investigated by slow positron-beam doppler broadening spectroscopy (DBS) and coincidence doppler broadening spectroscopy (CDB), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD results indicate that the existence of the β phase enhances the solid solubility of hydrogen in Ti-Mo alloy. The metastable γ-TiH hydrides are formed in pure titanium after hydrogen ion irradiation, while no hydride is found in Ti-Mo alloy under the same irradiation conditions. Moreover, DBS and CDB results show that hydrogen vacancy-complexes are formed in Ti and Ti-Mo alloys after hydrogen ion irradiation. Calculated doppler curves trend qualitatively agrees well with the experimental results. The TEM results show lower defect concentration and smaller defect sizes in Ti-Mo alloy with (α + β) than pure titanium. The addition of molybdenum significantly refines the grains and increases the density of the interface, which plays an important role in the management of irradiation-induced defects.

Understanding hydrogen solubility and free volume characteristics in charge-transfer phthalonitrile prepolymer and polyimide blend membranes

The increasing demand for hydrogen production has necessitated the development of H2-selective membranes. Polyimides are excellent membrane materials for gas separation; however, commercial polyimides generally lack sufficient H2 selectivity due to their low H2 affinity. Understanding the relationship between gas transport properties and free volume microstructure is critical to advancing H2-selective membrane design. Herein, we report a facile material strategy to adjust the free volume characteristics and H2 separation performance via blending Matrimid (PI) and crosslinkable resorcinol-based phthalonitrile prepolymer (RPN) with electron donor/acceptor properties. The novel RPN30/PI70 membrane exhibits H2/N2 and H2/CO2 permselectivity of 1637 and 66.4, respectively, with H2 permeability of 2.7 Barrer in pure gas test, surpassing Robeson upper bounds (2008). The increased H2 permselectivity of RPN/PI membranes was attributed to the narrowed free volume size and distribution, giving rise to the considerably improved H2 solubility and selectivity of the blends. Moreover, the H2 permeability of crosslinked RPN30/PI70 membranes can be further improved via thermal treatment. The H2/CO2 mixed-gas test reveals that the H2 gas separation performance of the RPN30/PI70 membrane is influenced by plasticization effect and competitive sorption. This study demonstrates a new versatile strategy for designing high-performance hydrogen-selective polymeric membranes.

On the Solubility of Hydrogen in Metals and Alloys

On the Solubility of Hydrogen in Metals and Alloys

Intelligence-based simulation of solubility of hydrogen in bitumen at elevated pressure and temperature: Models optimization using fireworks algorithm

This research aimed to model the solubility of hydrogen in Athabasca bitumen as crude oil byproduct using temperature and pressure as input features. Correlative models based on machine learning were developed and validated via comparing with measured data of hydrogen solubility in bitumen at elevated pressure and temperature. Three ensemble machine learning algorithms based on Decision Trees were trained and evaluated: Extra Trees, Random Forest, and Adaboost DT, with hyperparameters optimized using the Fireworks Algorithm (FWA). The Extra Trees model (FWA-ET), with 26 trees achieved the highest performance, with an R2 score of 0.986, RMSE of 0.051, and AARD% of 6.981. The Random Forest model (FWA-RF) with 9 trees achieved an R2 score of 0.838, RMSE of 0.194, and AARD% of 27.830. The Adaboost DT model (FWA-ADT) with 153 trees achieved an R2 score of 0.846, RMSE of 0.142, and AARD% of 21.264. The results suggest that ensemble models based on Decision Trees can effectively predict the solubility of hydrogen in heavy hydrocarbons. Hyperparameter optimization using FWA improved model performance. The Extra Trees model achieved the highest R2 score, lowest RMSE, and AARD%. These findings may provide insights for the oil and gas industry to estimate hydrogen solubility in hydrocarbons.

Solubility of hydrogen in Ab alloy

In this work, the solubility of hydrogen is studied using the method of average energies, quasi-chemical approximation, as well as by introducing the consideration of the crystal molecular field of interstitial hydrogen atoms. By using the configuration method, the solubility of the H interstitial impurity in a binary alloy AB of the impurities which has a hexagonal symmetry structure of type B81 was investigated. It was shown that the effect of order on the solubility of interstitial impurities in an alloy is stronger in the case of filling octahedral interstices which is important, because can make it possible to choose the desired system with the hydrogen yield required for practical purposes.

A novel method to design Nb(W)–Ti–Co(Fe) alloy membrane with high hydrogen permeability and strong resistance to hydrogen embrittlement

A hydrogen permeable Nb43W5Ti27Co20Fe5 alloy membrane was designed and its microstructure and hydrogen transportation performances were systematically studied. W mainly dissolves into primary body-centered cubic (bcc)-(Nb) phases, while Fe is captured in eutectic structures. Substituting Nb with W leads to a substantial reduction in hydrogen solubility and substituting Co with Fe negligibly affects hydrogen solubility. The W and Fe substitutions contribute to an enhanced intrinsic hydrogen diffusion coefficient D∗. The designed Nb43W5Ti27Co20Fe5 alloy membrane exhibits lower hydrogen solubility and higher hydrogen permeability at temperatures below 623 K than that of the original Nb48Ti27Co25 alloy membrane. No hydrogen-induced failures were found for the designed Nb43W5Ti27Co20Fe5 alloy membrane during cooling to room temperature and under long-term hydrogen permeation at 673 K for 72 h, whereas the original alloy membrane failed at 444 K during cooling to room temperature and after 19 h during hydrogen permeation at 673 K. The designed Nb43W5Ti27Co20Fe5 alloy membrane exhibits high hydrogen permeability and strong resistance to hydrogen embrittlement.

Mechanistic evaluation of the reservoir engineering performance for the underground hydrogen storage in a deep North Sea aquifer

Underground hydrogen storage (UHS) in aquifers, salt caverns and depleted hydrocarbon reservoirs allows for the storage of larger volumes of H2 compared to surface storage in vessels. In this work, we investigate the impact of aquifer-related mechanisms and parameters on the performance of UHS in an associated North Sea aquifer using 3D numerical compositional simulations.Simulation results revealed that the aquifer's permeability heterogeneity has a significant impact on the H2 recovery efficiency where a more homogenous rock would lead to improved H2 productivity. The inclusion of relative permeability hysteresis resulted in a drop in the H2 injectivity and recovery due to H2 discontinuity inside the aquifer which leads to residual H2 during the withdrawal periods. In contrast, the effects of hydrogen solubility and hydrogen diffusion were negligible when studied each in isolation from other factors. Hence, it is essential to properly account for hysteresis and heterogeneity when evaluating UHS in aquifers.

Degradation modelling and reliability analysis of PEM electrolyzer

Reliability is critical to enable the safe production of hydrogen as fuel. Efficient hydrogen production depends on the reliability of electrolytic cells termed an electrolyzer. The polymer electrolyte membrane (PEM) electrolyzer is one of the most promising hydrogen production technologies. However, hydrogen solubility, diffusivity, and partial pressure differences between the flow channels could affect the reliability and safety of the PEM. The operating conditions could also introduce safety issues inside the PEM electrolyzer due to membrane degradation or thinning. A degraded membrane will initiate the hydrogen produced at the cathode, tends to cross over to the anode and may cause an internal explosion should the mixture of hydrogen-oxygen get minimum ignition energy. Therefore, investigating hydrogen gas cross-over is - imperative to ensure the reliability and safety of the PEM electrolyzers. This paper presents a novel reliability model of PEM electrolyzers, considering readily observable variables relevant to the issue. The Bayesian structural equation defines the causal relationships to variables representing failure scenarios: membrane drying and hot spot formation. The study identifies that the current density and the quantity of water at PEM's anode are two critical variables responsible for the reliability of the PEM electrolyzers. Monitoring and managing these variables will help ensuring PEM's operational safety and reliability.

Solubility study of hydrogen in direct coal liquefaction solvent based on quantitative structure–property relationships model

Direct coal liquefaction (DCL) is an important and effective method of converting coal into high-value-added chemicals and fuel oil. In DCL, heating the direct coal liquefaction solvent (DCLS) from low to high temperature and pre-hydrogenation of the DCLS are critical steps. Therefore, studying the dissolution of hydrogen in DCLS under liquefaction conditions gains importance. However, it is difficult to precisely determine hydrogen solubility only by experiments, especially under the actual DCL conditions. To address this issue, we developed a prediction model of hydrogen solubility in a single solvent based on the machine-learning quantitative structure–property relationship (ML-QSPR) methods. The results showed that the squared correlation coefficient R2 = 0.92 and root mean square error RMSE = 0.095, indicating the model’s good statistical performance. The external validation of the model also reveals excellent accuracy and predictive ability. Molecular polarization (α) is the main factor affecting the dissolution of hydrogen in DCLS. The hydrogen solubility in acyclic alkanes increases with increasing carbon number. Whereas in polycyclic aromatics, it decreases with increasing ring number, and in hydrogenated aromatics, it increases with hydrogenation degree. This work provides a new reference for the selection and proportioning of DCLS, i.e., a solvent with higher hydrogen solubility can be added to provide active hydrogen for the reaction and thus reduce the hydrogen pressure. Besides, it brings important insight into the theoretical significance and practical value of the DCL.

Towards quantitative analysis of deuterium absorption in ferrite and austenite during electrochemical charging by comparing cyclic voltammetry and cryogenic transfer atom probe tomography

Hydrogen embrittlement mechanisms of steels have been studied for several decades. Understanding hydrogen diffusion behavior in steels is crucial towards both developing predictive models for hydrogen embrittlement and identifying mitigation strategies. However, because hydrogen has a low atomic mass, it is extremely challenging to detect by most analytical methods. In recent years, cryogenic-transfer atom probe tomography (APT) of electrochemically-deuterium-charged steels has provided invaluable qualitative analysis of nanoscale deuterium traps such as carbides, dislocations, grain boundaries and interfaces between ferrite and cementite. Independently, cyclic voltammetry (CV) has provided valuable analysis of bulk hydrogen diffusion in steels. In this work, we use a combination of CV and cryogenic-transfer APT for quantitative analysis of deuterium pickup in electrolytically charged pure Fe (ferrite) and a model austenitic Fe18Cr14Ni alloy without any second phase. The high solubility and low diffusivity of hydrogen in austenite versus ferrite and potential influence of oxide layer are highlighted to result in clear observable signatures in CV and cryogenic-transfer APT results. The remaining challenges and pathway for enabling quantitative analysis of hydrogen pick up in steels is also discussed.

Geochemical modelling on the role of redox reactions during hydrogen underground storage in porous media

Underground Hydrogen Storage (UHS) in porous media appears to be a promising means for large-scale hydrogen storage, underpinning the full-scale of hydrogen supply chain development. Hydrogen-brine-rock interactions play an important role in hydrogen conversion and contamination during hydrogen cycling process. While the redox reaction triggered by injected H2 and pre-existing O2 is unique in UHS compared to other types of gas subsurface storage, few research have been done to understand the role of redox reactions in hydrogen solubility, pH, and fewer works have looked beyond its process on hydrogen conversion and contamination, which may affect the stored H2 purity and storage efficiency. In this context, we examined the redox reactions on hydrogen-brine-minerals (e.g., calcite, siderite, quartz and pyrite) reactions as a function of dissolved oxygen concentration (from 5.5 to 5500 ppm), temperature, and pressure through geochemical modelling using geochemical solver PHREEQC.Our results showed that increasing dissolved oxygen concentration from 5.5 to 5500 ppm resulted in negligible impact on hydrogen solubility and pH for all tested minerals. As the sensitive minerals, siderite and calcite can react with H2 through the redox process, leading up to a certain hydrogen loss at the pressure of 20 MPa, respectively. Meanwhile, quartz and pyrite are insensitive minerals to hydrogen, causing less than 0.2% hydrogen loss at the same pressure condition. Our results indicate that the mineral oxidation due to the pre-existing O2 dissolved in formation brine played a negligible role in H2-brine-rock interactions. The results also showed that carbonate minerals such as siderite and calcite may act as electron acceptors, which triggered hydrogen dissociation and thus formed a strong reduction environment based on PHREEQC geochemical database. This process likely causes measurable hydrogen loss associated with abiotic geochemical reactions for the lifetime of the underground hydrogen storage operation. Taken together, we suggest that clean standstone reservoirs will signifcantly reduce the hydrogen conversion and contamination during underground hydrogen storage from abiotic geochemical perspective.

Analysys of the performance a PEM-type electrolyzer in variable energy supply conditions

In this article, the main variables related to the performance of a proton exchange membrane-type electrolyzer are analyzed along with the risk of explosion for different operating conditions, notably when the electrolyzer works with a variable solar energy power supply and at high pressure. A novel mathematical model was developed that considers all mass transport phenomena through the membrane electrode assembly (MEA) for water, hydrogen, and oxygen, as well as the water evaporation in the anode and cathode channels. The main findings of this work are that for a solar energy supply operating at high pressure, the electrolyzer cannot function safely throughout the day, since in the hours when solar irradiation is lower, low current densities favor high hydrogen concentrations at the anode. Finally, it was found that greater thicknesses of the membrane increased the explosion risk due to the increase in the MEA temperature and therefore the hydrogen solubility.

Early-stage structure and evolution mechanism of hydrogen supersaturated surface layers on tungsten under low-energy plasma exposure

Trapping at irradiation-induced defects significantly enhances hydrogen-isotope retention in metals with low hydrogen solubility. Here, we present the first microscopic observation of nanocavity formation on tungsten surfaces exposed to low-dose hydrogen plasma at room temperature. The nanocavities exhibit very high aspect ratios between their lateral size L and thickness ω (L/ω: 60-90) and represent the predominant microstructural defects in the early development stage of the hydrogen supersaturated surface layer on hydrogen plasma-irradiated tungsten (see Nucl Fusion57 (2017) 016026, Acta Mater201 (2020) 55). We also quantify the vacancy yield in tungsten under hydrogen irradiation with ion energies below the threshold to create stable Frenkel pairs. Such defect production at sub-threshold energy is conventionally deemed impossible, but we consider that the exposed surface acts as a defect sink with strong absorption bias for mobile self-interstitial atoms from temporarily created Frenkel pairs. This results in a high excess of immobile vacancies in the nanometer-thin surface layer and their agglomeration causes the evolution of large, disc-like nanocavities.

The formation of hydride and its influence on Ti–6Al–4V alloy fracture behavior

The fracture mechanism of hydrogen charged Ti–6Al–4V has been investigated through a multianalytical approach. The difference in hydrogen solubility between β phase (high solubility) and α phase (low) governs the formation and growth pattern of titanium hydrides, and determine the fracture mode of Ti–6Al–4V. Depending on the hydrogen charging extent, the penetration of hydrogen and distribution of hydrides can be divided into three stages. In the initial stage hydrogen diffuses mainly into the β phase, as judged from its increase in Volta potential, and with no hydrides formed. Failure analysis after tensile tests exhibits plastic behavior and a fracture surface with mainly dimples. In the subsequent transition stage, hydrides are formed at the α/β interfaces and along α grain boundaries. More initial cracks occur in the brittle hydrides and the fracture surface transforms from dimple to quasi-cleavage. In the final stage a layer of uniformly distributed hydride is produced on the surface and within the α phase. Supported by nanoindentation measurements, the plasticity of the charged sample diminishes with hydrogen charging time, and an intergranular-transgranular mixed fracture is observed. Overall, the study forms clear evidence that the distribution and cracks of hydrides influence the fracture mode of the Ti-6A-4V alloy.

Effect of additive manufacturing and subsequent heat and/or surface treatment on the hydrogen embrittlement sensitivity of 316L austenitic stainless steel

Austenitic stainless steels (ASS) offer attractive characteristics for use in hydrogen service, such as low hydrogen diffusivity and high solubility. The role of the production process is, however, still unclear. Especially the effect of additive manufacturing (AM) on the hydrogen interaction is not extensively researched yet. The present work compares the hydrogen embrittlement sensitivity of conventional (cold rolled and annealed) and additive manufactured 316L ASS and evaluates the possible advantage of performing a heat treatment and/or reducing the surface roughness post printing. AM increases the hydrogen solubility but the hydrogen diffusivity was only slightly reduced. The heat treatment reduced the hydrogen solubility of the AM materials and significantly increased the hydrogen diffusivity. Despite these observations, the conventional 316L ASS shows a higher hydrogen embrittlement (HE) sensitivity compared to AM316L. This is linked to the increased hydrogen-assisted cracking sensitivity of conventional 316L ASS. The heat treated microstructure behaves similarly as the as-built material in terms of HE sensitivity, while a major improvement is observed when the surface oxide layer formed during the heat treatment is maintained since this reduces hydrogen absorption. Surface polishing intensifies the HE sensitivity which is linked to a higher surface hydrogen concentration leading to more crack initiation.

Fundamental properties of hydrogen at PdCu–Mo2C interfaces from first principles calculations

First principles calculation have been carried out to comparatively examine the hydrogen solubility, hydrogen diffusion, and hydrogen permeability, as well as the interface strength at the PdCu(110)-Mo2C(001) interfaces region. It is found that the addition of Mo2C as a coating and support could increase the hydrogen solubility of BCC PdCu membrane. On the contrary, the formation of PdCu(110)-Mo2C(001) interfaces would hinder the hydrogen diffusion, and hydrogen diffusion through the PdCu region of Mo2C(001)/PdCu(110) interface is relatively easier than that of PdCu(110)/Mo2C(001) interface. Moreover, when the Mo2C is used as the catalytic layers, the formation of Mo2C(001)/PdCu(110) interface would be profit for hydrogen permeation. Calculations also reveal that the interface strength would be reduced when hydrogen permeation across the PdCu(110)-Mo2C(001) interfaces region. The predicted results could provide a deep understanding of the effects of formations of PdCu(110)-Mo2C(001) interfaces on hydrogen behaviors, and Mo2C/PdCu composite membranes could be regarded as a nice candidate for hydrogen permeation.