Hydrogen Diffusion Coefficient Research Articles

Impact of SOFC anode carbon deposition and hydrogen adsorption on the cell performance by molecular simulation.

This study primarily investigates the changes in carbon adsorption capacity and hydrogen adsorption capacity on the anode catalyst surface when using methane fuel and mixed gas fuel as the anode fuel for SOFC systems. To reduce the carbon adsorption capacity of the commonly used anode catalyst-nickel-based catalysts-towards hydrocarbon fuels, copper and gold are doped into the nickel-based catalysts to compare the effects on carbon and hydrogen adsorption capacities. Moreover, aside from calculating the carbon and hydrogen adsorption capacities, this project also evaluates the impact of mixed gas effects and doping effects on SOFC performance through the analysis of hydrogen diffusion coefficients and performance polarization curves. The findings reveal a noteworthy enhancement in the diffusion coefficient of syngas within the Au-doped Ni catalyst, showing an improvement of up to 45.46% at 973K. Furthermore, the electrical power generated by syngas in the Au-doped Ni catalyst at 973K demonstrates an increase of up to 12.06%. This study primarily employs DFT to calculate the carbon and hydrogen adsorption energies on methane, utilizing CASTEP for the calculations. During these calculations, the adsorption energy is determined through a three-layer surface approach, in conjunction with the Kohn-Sham equations, combining the Generalized Gradient Approximation and ultrasoft pseudopotentials for TS-search calculations. On the other hand, this project will analyze the diffusion coefficient of hydrogen on the anode catalyst using MD methods combined with the ReaxFF potential field, with GULP being utilized to complete all dynamics calculation theories. Finally, the project will analyze the performance of SOFC cells, incorporating relevant numerical equations with Matlab for numerical analysis.

Theoretical study on hydrogen permeation and fault slip of γ-Ni/γ'-Ni3Al interface with alloying elements (Zr, Nb, Ru, Re, and Hf)

In order to elucidate the role of hydrogen behavior at γ-Ni/γ'-Ni3Al interface with alloying elements, we performed comprehensive research of the permeation and slip properties by using DFT calculations. The result figures out that the alloying elements (Zr, Nb, Ru, Re, and Hf) tends to occupy corner-point sites in γ-Ni phase, while Re has the lowest substitution formation energy. The octahedron interstitial site is the favorable position for hydrogen adsorption due to its lower solution energy compared to the tetrahedron site. The diffusion energy barrier of hydrogen follows the influence order of Zr < Ru< Hf < Re < Nb. Meanwhile, Nb-doped interface has the highest hydrogen diffusion coefficient and permeability compared to other doped interfaces. By analyzing the partial density of states, the hybridization between Re-d orbital and neighbor Ni-d orbital is conducive to affect the permeability behavior of hydrogen. The generalized stacking fault energy reveals that all the alloying elements can improve the creep strength of γ-Ni/γ'-Ni3Al interface. As a barrier, Hf element is more effective to improve the dislocation slip resistance. These results can help people deepen the understanding of hydrogen behavior with alloying elements at the γ-Ni/γ'-Ni3Al interface and provide fundamental theories data for the further design of Ni-based superalloy.

Characterization of hydrogen embrittlement sensitivity of 18CrNiMo7-6 alloy steel surface-modified layer based on scratch method

PurposeThe purpose of this paper is to assess the hydrogen embrittlement sensitivity of carbon gradient heterostructure materials and to verify the reliability of the scratch method.Design/methodology/approachThe surface-modified layer of 18CrNiMo7-6 alloy steel was delaminated to study its hydrogen embrittlement characteristics via hydrogen permeation, electrochemical hydrogen charging and scratch experiments.FindingsThe results showed that the diffusion coefficients of hydrogen in the surface and matrix layers are 3.28 × 10−7 and 16.67 × 10−7 cm2/s, respectively. The diffusible-hydrogen concentration of the material increases with increasing hydrogen-charging current density. For a given hydrogen-charging current density, the diffusible-hydrogen concentration gradually decreases with increasing depth in the surface-modified layer. Fracture toughness decreases with increasing diffusible-hydrogen concentration, so the susceptibility to hydrogen embrittlement decreases with increasing depth in the surface-modified layer.Originality/valueThe reliability of the scratch method in evaluating the fracture toughness of the surface-modified layer material is verified. An empirical formula is given for fracture toughness as a function of diffused-hydrogen concentration.

Aluminum-silver nanoalloys supported on a nitrogen-doped edge of bilayer graphite as thermal engineering device for H2 storage

Molecular dynamics simulations suggest that doping nitrogen in the edges of bilayer graphite as a support material near room temperature significantly enhances hydrogen storage on aluminum nanoparticles compared to silver nanoparticles. This finding underscores aluminum's potential for industrial hydrogen storage applications. Hydrogen storage on aluminum and silver nanoparticles, and aluminum-silver nanoalloys supported on bilayer graphite (BG) and nitrogen-doped bilayer graphite edges (NDBGE) exhibits a diminishing trend with increasing temperature. Particularly noteworthy is the observation that higher concentrations of aluminum doping in silver-aluminum nanoalloys, when supported on NDBGE, lead to a decrease in hydrogen storage across various temperatures. Using NDBGE as a supporting material leads to a substantial increase in hydrogen storage on aluminum-silver nanoalloy surfaces, achieved through thermal engineering within the temperature range: 300 K to 350 K. Here, the combination of thermal engineering and nitrogen doping in bilayer graphite edges provides a viable approach to engineer larger aluminum nanoparticles, aligning with international standards criteria such as those set by the United States Department of Energy (SUSDOE) for hydrogen storage. Bilayer graphite, when utilized as a support for aluminum metals, facilitates thermal engineering across a broad temperature range, aligning with SUSDOE's objectives. Concerning the diffusion coefficient of hydrogen, there is no consistent trend observed as a function of temperature for aluminum and silver nanoparticles supported on NDBGE. However, in the case of silver-aluminum nanoalloys supported on NDBGE, hydrogen diffusion increases with temperature. The general trend for hydrogen diffusion on aluminum surfaces versus temperature agrees with available experimental data. Current simulation results predicting a decrease in hydrogen adsorption on aluminum surfaces with increasing temperature also confirm available experimental findings.

Hydrogen diffusivity in dislocation, grain boundary, and lattice of α-Fe based on electrochemical hydrogen permeation experiments and Maxwell-Garnett calculations

We elucidate the hydrogen diffusivity in α-Fe with different dislocation densities, grain sizes, and textures obtained by different annealing after cold rolling based on electrochemical hydrogen permeation experiments and Maxwell-Garnett calculations. A unique inflection point was found to calculate the hydrogen diffusion coefficient, which reflects the threshold from accelerating to decelerating hydrogen diffusion. Texture has significant influences on hydrogen diffusion, and hydrogen atoms in α-Fe lattice diffuse along <111> direction much slower than in other directions. Based on Maxwell-Garnett calculations, the hydrogen diffusion coefficients of dislocations, grain boundaries, and α-Fe isotropic lattice are 4.4×10−4, 2.3×10−4, and 2.5×10−10 m2/s, respectively.

Hydrogen adsorption and diffusion behavior in kaolinite slit for underground hydrogen storage: A hybrid GCMC-MD simulation study

Underground hydrogen storage (UHS) in reservoirs offers the opportunity for large-scale and long-term storage of hydrogen. In order to understand the fundamental mechanisms of hydrogen storage and transportation, it is crucial to study the adsorption and diffusion behavior of hydrogen in reservoirs. By utilizing a hybrid GCMC and MD simulation procedure, we investigated the adsorption and diffusion behavior of hydrogen in kaolinite slit with pore sizes ranging from 1 to 20 nm at pressures up to 30 MPa and temperatures ranging from 303 to 423 K. Hydrogen distribution, excess adsorption, diffusion coefficient, and gas–solid interaction energy were analyzed in relation to pore size, temperature, pressure, and mineralogy. When pores are larger than 5 nm, most of the hydrogen is located in the bulk phase, resulting in insignificant hydrogen loss due to adsorption. Therefore, reservoirs with pores larger than 5 nm are suitable for UHS. Reservoirs with low temperatures and high hydrogen pressures are conducive to UHS, but the hydrogen mobility is reduced. The mineralogy of the formation results in pore surfaces with different charge properties, which significantly affects hydrogen storage. Although van der Waals interaction dominates the gas–solid interaction, Coulomb interaction remains important. The negatively charged pore surface mitigates the gas–solid Coulomb interaction, thereby preventing hydrogen loss through adsorption. This study enhances our understanding of hydrogen storage mechanisms in subsurface porous media and elucidates the influence of various factors. Consequently, it provides a theoretical framework for selecting UHS sites.

The feasibility of hydrogen storage in aquifers: A molecular dynamics simulation

Geological hydrogen storage could be an effective method for solving energy demand and climate change challenges. We focus on hydrogen diffusion in carbonate slits via molecular dynamics under subsurface conditions. We investigate the influence of pore size, moisture content, and salinity on hydrogen diffusion process. The results demonstrate that high moisture content reduces the diffusion coefficient of hydrogen due to the form of water bridge and hydrogen cluster. The impact of salinity is observed only under high moisture content conditions. Specially, CaCl2 and MgCl2 are more suitable than NaCl for hydrogen storage. Hydrogen storage is more suitable in lower NaCl concentration while it is more suitable in a higher Na2SO4 concentration. Because interfacial tension of hydrogen-salt solution could be affected by ion concentration. These results demonstrate that hydrogen diffusion could be regulated by changing salinity for high water cut reservoir. This job could provide valuable guidance for underground hydrogen storage.

Reliability-based life prediction method for concrete sewage pipelines under microbial attack

The durability of concrete sewage pipelines decreased for microbial attack. In this study, a method for life prediction of concrete sewage pipes under microbial-induced attack was developed by combining numerical simulation with theoretical analysis. A mathematical model of the corrosion depth of microbial erosion of concrete was constructed based on the cumulative model of sulfate concentration on the surface of sewage pipes and verified the applicability by comparing it with the experimental results. The Monte Carlo (MC) life prediction method and Fuzzy- Monte Carlo (F-MC) life prediction method for concrete sewage pipes was established based on the reliability theory and fuzzy methodology. Several factors are considered as random variables and analyzed parametrically, including hydrogen sulfide concentration (SH2S), diffusion coefficient (D), and thickness of the concrete cover (CC). In addition failure event was consider as a fuzzey event. It was found that: The increasing SH2S and D result in higher failure rates and lower service life, however as the increase of the thickness of CC, there is the opposite effect. The results of the numerical simulations revealed a NR between the three kinds of parameters and the probability of failure of sewer pipes. Compared with the MC model, the F-Mc model produces more conservative but not minimal different results, which confirms the applicability of the F-MC model.

Hydrogen diffusion and hydrogen embrittlement of a 1500 MPa hot-stamped steel 22MnB5 in different austenitizing conditions

We investigated the influence of hydrogen on a 1500 MPa hot-stamped steel 22MnB5 with different prior austenite grain size (PAGS, ranging from 14.0 μm to 22.2 μm), which were produced by precise control of the austenitizing temperature and time. All steel specimen exhibited a significant reduction of ductility (e.g., by 70%) and a small decrease in ultimate tensile strength (≤15%), measured using the linearly increasing stress test. The effect of PAGS on hydrogen embrittlement of the hot-stamped steel was not significant for these test conditions. Martensite with smaller PAGS exhibited a slightly lower hydrogen diffusion coefficient. Fracture for all steel variants after yielding occurred for hydrogen contents greater than those that actually occur during service.

Applied electric field to repair metal defects and accelerate dehydrogenation

Repairing metal micro-defects at the atomic level is very challenging due to their random dispersion and difficulty in identification. At the same time, the interaction of hydrogen with metal may cause hydrogen damage or embrittlement, endangering structural safety. As a result, it is critical to speed up the dehydrogenation of hydrogen-containing materials. The applied electric field can repair the vacancy defects of the material and accelerate the dehydrogenation of the hydrogen-containing metal. The influence of the external environment on the diffusion coefficient of hydrogen in polycrystalline metals was researched using molecular dynamics in this article, and the mechanism of hydrogen diffusion was investigated. Simultaneously, the mechanical characteristics of Fe3Cr alloy were compared during typical heat treatment and electrical treatment. The effect of temperature, electric field strength, and electric field direction on the diffusion coefficient was investigated using orthogonal test analysis. The results demonstrate that temperature and electric field strength have a significant impact on the diffusion coefficient. The atom vibrates violently as the temperature rises, breaking past the diffusion barrier and completing the atomic transition. The addition of the electric field adds extra free energy, decreases the atom’s activation energy, and ultimately enhances the atom’s diffusion coefficient. The repair impact of vacancy defects under electrical treatment is superior to that of typical annealing treatment for polycrystalline Fe3Cr alloy. The electric field can cause the dislocation to migrate, increasing the metal’s toughness and plasticity. This research serves as a useful reference for the electrical treatment of metal materials and offers a method for the quick dehydrogenation of hydrogen-containing materials.

A comprehensive study on the kinetics and isotherms of D2/H2 adsorptive separation using pure and composite Cu-BDC-NH2 MOFs at 77 K

Pure and composite Cu-Amino-terephthalate MOF has been produced by ultrasound wave to evaluate the adsorption capacity and adsorptive separation of D2 and H2 at 77 K up to 1000 mbar. The frameworks are characterized by XRD, SEM, FTIR, ICP, BET, and EDX analysis. Separation studies were performed using idealized adsorption solution theory (IAST) and direct measurements. Isotherm studies showed the data had good agreement with the Langmuir model and the adsorption capacity of deuterium was greater than hydrogen in all samples. Linear Driving Force (LDF) model was applied to investigate the effective diffusion coefficients of deuterium and hydrogen in the frameworks. The LDF model showed hydrogen molecules diffused faster than deuterium molecules in all frameworks. In the adsorption enthalpy studies, there was a slight difference between deuterium and hydrogen adsorption energy. In this regard, Cu-BDC-NH2@rGO showed a higher adsorption enthalpy difference compared to Cu-BDC-NH2. Finally, the D2/H2 selectivity of the composite framework was greater than the pure one. Regarding this matter, the Cu-BDC-NH2@rGO MOF showed a maximum selectivity factor of about 2.2 at 77 K and 1000 mbar based on the IAST model.

Effect of ball milling on the structure and electrochemical hydrogen storage properties of a RE-Mg-Ni alloy

RE-Mg-Ni alloy is considered a highly promising anode material for the next generation of MH-Ni batteries. However, the low cycle life, fast performance, and high manufacturing cost of this ideal MH-Ni battery anode material have become obstacles to its optimization. In this work, an as-cast La0.7Sm0.3MgNi3.6Co0.4 superlattice alloy was prepared by vacuum medium frequency induction melting. Then, La0.7Sm0.3MgNi3.6Co0.4 + 10 wt% Ni (0–2 h) composite hydrogen storage alloys with excellent properties were prepared by adding a catalyst (Ni) and conducting ball milling. XRD, SEM, and HRTEM were conducted to analyse the phase compositions, microstructures and macrostructures of the samples. The experimental results showed that with the increase in ball milling time, the microstructural characteristics of the alloy changed, such as the phase abundance, grain refinement, particle size reduction, and amorphous structure increase, directly leading to the change in electrochemical performance. The discharge capacity (Cmax) of the sample decayed from 264.0 mAh/g to 219.1 mAh/g, the cycle stability (Sn) gradually increased with the extension of the grinding time, and the rate discharge performance first increased and then decreased. When the grinding time was 1 h, the best performance was HRD900 = 36.53%. The critical factors affecting the dynamic performance, such as the charge transfer resistance (Rct), limiting current density (IL), and hydrogen diffusion coefficient (D), all exhibited the same trend and reached their respective optimal values at 1 h.

A novel solution to improve static and dynamic retention characteristics by enhancing hydrogen passivation with in situ LD-TEOS/TEOS dual layer

We proposed a novel solution to improve both static and dynamic retention characteristics by additional etching of the thickness of Silicon Boron Nitride (SIBN), stopper when oxide etch, with in situ dual low deposition-tetraethyl orthosilicate (LD-TEOS)/TEOS Dual layer. As Dynamic Random Access Memory Cells shrink, it is difficult to obtain reliable retention properties, so it becomes more significant to reduce the number of interface trap (Nit) by hydrogen passivation. In this work, Nit decreased by reducing the thickness of SIBN, which has low hydrogen diffusion coefficients, improve the static and dynamic retention characteristics simultaneously through enhancing hydrogen passivation with in situ LD-TEOS Dual layer compensating for Metal contact to Other Bit line pad distance margin risk.

Influence of physical properties of weld metal on hydrogen diffusion into the heat affected zone of heterogeneous welded joints

The paper presents the analytical solution of one-dimensional problem on hydrogen diffusion in butt heterogeneous welded joints. Such parameters as welded joint thickness, weld thickness, diffusion coefficients, solubilities and initial concentrations of hydrogen in the weld metal and base metal have been taken into account. The effects of microstructure on hydrogen kinetics in homogeneous and heterogeneous welded joints are considered. It is shown that hydrogen concentration in the heat affected zone (HAZ) to a great extent depends on the ratios of the initial concentrations, hydrogen diffusion coefficients and solubilities in the weld metal to those in the base metal. The concentration of hydrogen in the HAZ decreases by three orders of magnitude when welding martensitic steel with austenitic electrodes as compared to homogeneous joints.

Underground Hydrogen Storage Safety: Experimental Study of Hydrogen Diffusion through Caprocks

Underground Hydrogen Storage (UHS) provides a large-scale and safe solution to balance the fluctuations in energy production from renewable sources and energy consumption but requires a proper and detailed characterization of the candidate reservoirs. The scope of this study was to estimate the hydrogen diffusion coefficient for real caprock samples from two natural gas storage reservoirs that are candidates for underground hydrogen storage. A significant number of adsorption/desorption tests were carried out using a Dynamic Gravimetric Vapor/Gas Sorption System. A total of 15 samples were tested at the reservoir temperature of 45 °C and using both hydrogen and methane. For each sample, two tests were performed with the same gas. Each test included four partial pressure steps of sorption alternated with desorption. After applying overshooting and buoyancy corrections, the data were then interpreted using the early time approximation of the solution to the diffusion equation. Each interpretable partial pressure step provided a value of the diffusion coefficient. In total, more than 90 estimations of the diffusion coefficient out of 120 partial pressure steps were available, allowing a thorough comparison between the diffusion of hydrogen and methane: hydrogen in the range of 1 × 10−10 m2/s to 6 × 10−8 m2/s and methane in the range of 9 × 10−10 m2/s to 2 × 10−8 m2/s. The diffusion coefficients measured on wet samples are 2 times lower compared to those measured on dry samples. Hysteresis in hydrogen adsorption/desorption was also observed.

ПЕРСПЕКТИВИ РОЗВИТКУ ВОДНЕВОЇ ЕНЕРГЕТИКИ З МОЖЛИВІСТЮ ВІДНОВЛЕННЯ МЕМБРАН ДЛЯ ПАЛИВНИХ ЕЛЕМЕНТІВ ПІСЛЯ КОНТАКТУ З ВОДНЕМ

The prospects for the development of hydrogen energy and the influence of temperature on the change in the shape of the membrane for fuel cells in contact with hydrogen have been studied. It has been confirmed that the change in the shape of the plate from the α-PdHn gradient alloy develops in two stages. The experimental regularities of the change in the shape of the palladium membrane during operation in a hydrogen environment were investigated. It was determined that upon contact with hydrogen, a temporary gradient material "metal-hydrogen" is formed in the membrane, which causes the development of hydrogen concentration stresses, and the maximum change in the shape of the membrane, which occurs at a constant temperature, depends on the diffusion coefficient and the equilibrium solubility of hydrogen in palladium. However, when the temperature changes, the diffusion coefficient of hydrogen in palladium and the equilibrium concentration of hydrogen in palladium also change, which affects the temperature dependence of the final shape change of the membrane. This fact makes it possible to effectively plan and determine the time of hydrogen penetration into the membrane, control the change of shape and adjust the operating modes of the fuel cell. It is the equilibrium solubility of hydrogen in palladium and its diffusion coefficient when the temperature changes in the main that determine the maximum and final change in the shape of the membrane, and the temperature determines the fluctuation of the change in the shape of the membrane when the temperature of the hydrogen flow entering the chamber changes. Thus, the complete return of the membrane to its initial state at increased temperature clearly indicates the implementation of a coherent membrane bending mechanism. Upon completion of hydrogen saturation by the coherent mechanism under the conditions of reaching equilibrium with the gas phase, the original palladium membrane turns out to be transformed into a membrane of the equilibrium alloy α-PdHnо, which inherits the initial state of a pure palladium membrane. Therefore, to model the hydrogen penetration process in the fuel cell, it is necessary to know the gas flow rate, membrane permeability and gas temperature, as well as the diagram of the fuel cell where these processes take place. At the same time, scientists still hope for the future development of hydrogen energy, despite the existing difficulties. This requires additional research and development of new technologies to remove obstacles to the transition to hydrogen as a primary energy source

Electrochemical hydrogen permeation in wrought and electron beam melted Ti-6Al-4V alloys

Ti-6Al-4V is one of the most widely used titanium alloys. However, it is susceptible to hydrogen embrittlement, e.g. due to hydride formation. Hydrogen permeability through Ti-based alloys is affected by the rapid formation of hydride or oxide surface layers as well as by trapping in the bulk alloy. Here, we analyze and compare the electrochemical hydrogen permeation (EHP) through wrought and electron beam melted (EBM) Ti-6Al-4V alloys. Hydrogen diffusion coefficients are calculated from the permeation current transients. The effective diffusion coefficient of hydrogen in the wrought alloy is found to be an order of magnitude higher than in the AM’ed alloy. The different microstructures of the wrought and EBM alloys are found to play an important role in hydrogen distribution and phase transformation in the alloy. In the EBM alloy, hydrogen is distributed more uniformly and, consequently, more pronounce phase transformations occur, eventually leading to brittle cracking. In the wrought alloy, on the other hand, hydrogen is distributed unevenly in the bulk of the membrane, forming hydride clusters, most probably at α/β interphase boundaries. These findings suggest that the EBM Ti-6Al-4V alloy is more susceptible to HE than its wrought counterpart.

Molecular dynamics simulation of hydrogen diffusion into brine: Implications for underground hydrogen storage

Underground hydrogen storage has been the subject of extensive research recently. Hydrogen diffusion coefficient into brine critically affects hydrogen loss. However, the available data pertain to hydrogen diffusivity in pure water or NaCl solutions, with rare interpretations of temperature and salinity effects. In this paper, molecular dynamics simulations at realistic conditions were conducted to calculate these coefficients in various brines, particularly those containing divalent salts. The results indicate lower diffusivities at higher salinities and lower temperatures, the value being 7.29 × 10−9 m2/s at 323 K, increasing to 10.2 × 10−9 m2/s at 353 K for 1 molal NaCl solution. The diffusion coefficient decreases up to 38 % as the salinity increases from 1 to 5 molal. Besides, hydrogen diffusivity in MgCl2 solution is up to 60 % smaller than in NaCl solutions at the same molality. Radial distribution functions and hydrogen bond analyses confirm the results. This research provides new data for estimating hydrogen loss in aquifers or water-saturated caprocks.

Molecular dynamic simulation of H2-CH4 binary hydrate growth induced by methane hydrate

Hydrogen storage based on hydration is a promising technology, in which hydrogen molecules are captured in a three-dimensional cage structure formed by hydrogen bonds between water molecules. In this study, methane was selected as the accelerator guest molecule for hydrogen storage in hydrates, hydrogen-methane hydrate formation properties was investigated at 240 K and 110 MPa by molecular dynamic simulation. The combined TraPPE(CH4)-TIP4P/ice(H2O)-Diatomic(H2) force field was adopted. The molecular mechanism of the growth of CH4/H2 binary hydrates with different liquid methane concentrations (1.51–5.79 mol%) was explored, the effect of concentration on kinetic properties such as hydrate growth rate, hydrate hydrogen storage density, and properties related to cage occupancy and structural transformation were analysed. Any concentration of liquid-phase methane in this study increased hydrogen storage compared to a system without liquid methane. The growth rate of binary hydrates is related to the concentration and diffusion of liquid-phase methane: the higher the concentration of methane in liquid phase, the smaller the diffusion coefficient of hydrogen and water molecules in the solution, and the slower the growth rate of binary hydrates. The cage at the solid–liquid interface is preferentially occupied by hydrogen molecules, and the occupation process is gradually from the interface to the interior of the hydrate. At lower methane concentrations, the hydrate grows more uniformly along the interface. When the methane concentration is large, the hydrate not only grows along the interface, but also develops new nucleation sites in the liquid phase for growth, resulting in uneven growth of hydrate in the whole system. Methane acts as an accelerator to stabilize the cage while reducing diffusion. According to the hydrogen storage density of each system, it was found that hydrates have the best hydrogen storage efficiency when the concentration of methane in the liquid phase is 4.41 mol%. The transition from double-occupied cages to single-occupied cages indicated that the breakdown of the six-membered ring in the hydrate cage was the key to the passage of hydrogen molecules into and out of cages. This study will provide theoretical basis for the stable storage of H2 hydrate, and promote the industrial application of HHST technology.

Research on mathematical algorithm to determine the chemical diffusion coefficient of hydrogen in CaZrO3 based proton conductor at high temperature

To study hydrogen diffusion properties is of importance in design of new proton conductors. In the past, the chemical diffusion coefficient of hydrogen in proton conductor was usually obtained by the manual calculation method that largely depends on judgment ability of researchers, so calculation accuracy is difficult to control. To solve this problem, a mathematical algorithm and C language computer program were designed to calculate the chemical diffusion coefficient based on Fick's second law and Romberg numerical integral, in which the chemical diffusion coefficient is obtained by fitting measured electrical resistance relaxation curve based on. In addition, the algorithm can be extended to calculate the chemical diffusion coefficient in some special cases with incomplete measured electrical resistance relaxation curve or inaccurate measured values of R0 and R∞ based on modified algorithm of R0 and R∞, what cannot be handled by the manual calculation method. The chemical diffusion coefficient of self-synthesized Yb doped CaZrO3 proton conductor were calculated by using the algorithm and compared with the manual calculation method. The results show that the algorithm has the advantages of high precision and powerful computing function. The new algorithm is potential to be widely applied to the calculation of the chemical diffusion coefficient for hydrogen in proton conductors to replace the manual calculation method.