Hydrogen Permeation Experiments Research Articles

Applicability of Single-Layer Graphene as a Hydrogen-Blocking Interlayer in Low-Temperature PEMFCs.

Gas crossover is critical in proton exchange membrane (PEM)-based electrochemical systems. Recently, single-layer graphene (SLG) has gained great research interest due to its outstanding properties as a barrier layer for small molecules like hydrogen. However, the applicability of SLG as a gas-blocking interlayer in PEMs has yet to be fully understood. In this work, two different approaches for transferring SLG from a copper or a polymeric substrate onto PEMs are compared regarding their application in low-temperature PEM fuel cells. The SLG is sandwiched between two Nafion XL membranes to form a stable composite membrane. The successful transfer is confirmed by Raman spectroscopy and in ex situ hydrogen permeation experiments in the dry state, where a reduction of 50% upon SLG incorporation is achieved. The SLG composite membranes are characterized by their performance and hydrogen-blocking ability in a fuel cell setup at typical operating conditions of 80 °C and with fully humidified gases. The performance of the fuel cell incorporating an SLG composite membrane is equal to that of the reference cell when avoiding the direct etching process from a copper substrate, as remnants from copper etching deteriorate the performance of the fuel cell. For both transfer processes, the hydrogen crossover reduction of SLG composite membranes is only 15-19% (1.5 barabs) in the operating fuel cell. Further, hydrogen pumping experiments suggest that the barrier function of SLG impairs the water transport through the membrane, which may affect water management in electrochemical applications. In summary, this work shows the successful transfer of SLG into a PEM and confirms the effective hydrogen-blocking capability of the SLG interlayer. However, the hydrogen-blocking ability is significantly reduced when running the cell at the typical humidified operating conditions of PEM fuel cells, which follows from a combination of reversible interlayer alteration upon humidification and irreversible defect formation upon PEM fuel cell operation.

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.

Improved High-Temperature Stability and Hydrogen Penetration through a Pd/Ta Composite Membrane with a TaTiNbZr Intermediate Layer

In the hydrogen separation membrane, a dense TaTiNbZr amorphous layer was prepared between Pd and Ta to form a Pd/TaTiNbZr/Ta membrane system to prevent the reaction between Pd and Ta at high temperatures. The structural and chemical stability of the Pd/TaTiNbZr/Ta film system at high temperatures were investigated by annealing at 600 °C for 24 h. The high-temperature hydrogen permeation properties of the Pd/TaTiNbZr/Ta film systems were investigated by hydrogen permeation experiments at 600 °C after heat treatment for 6 h. The TaTiNbZr layer was significantly hydrogen-permeable. With the increase in the thickness of the barrier layer, the hydrogen permeability of Pd/TaTiNbZr/Ta decreased, but its hydrogen permeation flux was smaller than that of the highest value of Pd/Ta when it reached the steady state. The presence of the TaTiNbZr layer effectively blocks the interdiffusion between Pd and Ta to form TaPd3, improving the sustained working ability of the Pd/TaTiNbZr/Ta membrane system. The results show that TaTiNbZr is a candidate material for the intermediate layer to improve the high-temperature stability of metal-composite hydrogen separation membranes.

Preparation and performance study of waterborne epoxy resin/non-covalent modified graphene oxide hydrogen barrier coatings

Hydrogen embrittlement in hydrogen pipelines can cause severe economic losses and safety hazards, thus research on efficient hydrogen barrier coatings is of great importance. In this study, a more efficient and easily operable non-covalent modification method was employed to modify carboxymethyl chitosan (CMCS) onto graphene oxide (GO), resulting in a significant improvement in the dispersibility and uniform distribution of GO in waterborne epoxy resin. Subsequently, a hydrogen barrier coating was prepared by incorporating the modified GO into waterborne epoxy resin. The influence of different doping concentrations on the coating performance was investigated. The basic properties of the coatings were characterized using macroscopic analysis, SEM, contact angle measurements, adhesion tests and electrochemical techniques. The corrosion resistance and hydrogen barrier effect was evaluated through electrochemical hydrogen permeation experiments. Results showed that The modified graphene oxide has good compatibility with epoxy resin. When the content of CGO was 0.25 %, the dispersion was best. the CGO coatings has some corrosion resistance with approximately 10 MPa adhesive force and 105 Modular value at the beginning of immersion. The CGO coatings significantly improved the hydrogen resistance of ×80 steel. The lowest hydrogen permeation current density was observed at 0.25 wt% CGO concentration, which indicated optimal hydrogen permeation inhibition capability.

Effect of microstructure evolution induced by LP on hydrogen permeation behavior of 316L stainless steel

In order to investigate the hydrogen permeation behavior of 316L stainless steel during the microstructural evolution induced by laser peening (LP), an electrochemical hydrogen charging system for initial hydrogen charging of LPed and non-LPed specimen was developed. Afterward, the microhardness, residual stress, and microstructures of the samples were determined and analyzed. Finally, electrochemical hydrogen permeation experiments were undertaken to verify LP's influence on hydrogen permeation parameters of 316L. The results showed that LP reduced the hydrogen-induced hardening rate of the alloy and additionally invoked high magnitude compressive residual stress on its surface. At the layer close to the face of the specimen, the grain refinement rate was as high as 56.18%, which was accompanied by the appearance of high-density dislocations. Compared with the non-LPed sample, the hydrogen permeation time increased significantly, and the saturation current density in steady state hydrogen permeation also decreased gradually.

Nickel-Regulated Composite Cathode with Balanced Triple Conductivity for Proton-Conducting Solid Oxide Fuel Cells.

Proton-conducting solid oxide fuel cells (H-SOFCs) have the potential to be a promising technology for energy conversion and storage. To achieve high chemical compatibility and catalytic activity, nickel-doped barium ferrate with triple conducting ability is developed as cathodes for H-SOFCs, presenting an impressive electrochemical performance at intermediate temperatures. The cell performance with the optimized BaCe0.26 Ni0.1 Fe0.64 O3 -δ (BCNF10) composite cathode reaches an outstanding performance of 1.04Wcm-2 at 600°C. The high electrocatalytic capacity of the nickel-doped barium ferrate cathode can be attributed to its significant proton conductivity which is confirmed through hydrogen permeation experiments. Density functional theory (DFT) calculations are further conducted to reveal that the presence of nickel can enhance processes of hydration formation and proton migration, leading to improve proton conductivity and electro-catalytic activity.

Experimental study on the temperature dependence of gaseous hydrogen permeation and hydrogen embrittlement susceptibility of X52 pipeline steel

For the hydrogen-blended natural gas pipelines, operating temperature has an impact on the interaction between hydrogen and pipeline steel, thus influencing the hydrogen embrittlement (HE) risk of the pipelines. The effects of temperature on the hydrogen diffusion and HE behaviors of X52 pipeline steel were studied through a combination of in-situ gaseous hydrogen permeation experiments, SSRT tests, fracture morphology analysis and TDS tests. The temperature dependences of hydrogen permeation kinetics and HE susceptibility were established. The results show that within the temperature range from 20 °C to 60 °C, the hydrogen diffusivity increased significantly with rising temperature and satisfied the Arrhenius relationship. The subsurface hydrogen concentration reduced with temperature, which was due to the fact that the hydrogen diffusion increased faster than hydrogen absorption during the experimental temperature range. In addition, the HE index calculated in the SSRT tests and fracture morphologies indicate that the HE sensitivity of X52 steel increased with temperature, which was related to the higher amount of hydrogen trapped in the steel at 60 °C from the TDS analysis. This study can provide reference for the material safety evaluation under various operating temperatures of the hydrogen-blended natural gas pipelines.

Enhanced hydrogen embrittlement of steel by the premature hydrogen dissociation with the increasing inert gas pressure in hydrogen-containing mixtures

Regarding hydrogen embrittlement (HE) in the mixtures of hydrogen and inert gas, the results were understood mainly based on the partial hydrogen gas pressure. On the other hand, the effect of the total gas pressure has not been fully investigated. In this study, fatigue crack growth rate (FCGR) tests were conducted in high-purity hydrogen gas at different gas pressures. Also, the FCGR tests were conducted in hydrogen and nitrogen mixtures at different total gas pressures. The hydrogen partial pressure in the mixture was the same as the high-purity hydrogen. This was the first time that acceleration of the FCGR in the mixtures compared to that in the high-purity hydrogen was observed. To elucidate the mechanism of the enhanced HE in the mixtures, hydrogen permeation and hydrogen desorption experiments were carried out. Based on the results of these tests, the acceleration of the FCGR in the mixtures could be interpreted by the fast hydrogen entry rate, which may result in a higher local hydrogen concentration near the crack tip during a limited time. Density functional theory (DFT) calculations were performed to consider the total gas pressure effect on an atomic scale. The thrust force of other gas molecules in the mixtures made the hydrogen molecules enter the potential field of the iron surface sooner, advancing the dissociation of the hydrogen. This will increase the surface concentration of the hydrogen atoms.

Hydrogen-Induced Cracking in CGHAZ of Welded X80 Steel under Tension Load

X80 steel is extensively used in hydrogen environments and is susceptible to hydrogen embrittlement (HE). This paper studied the hydrogen-induced cracking (HIC) behavior in the coarse-grained heat-affected zone (CGHAZ) of X80 steel welds, through applying in situ hydrogen-charging tensile experiments, hydrogen permeation experiments, and various surface analysis techniques. It is shown that a few hydrogen atoms can significantly decrease a material’s elongation and reduction of area. When the heat input (HI) was 29.2 kJ/cm, the material had minor sensitivity to hydrogen embrittlement. The tensile fractures were ductile without hydrogen. However, the fracture surface exhibited brittle fracture with hydrogen. With increased HI, the HE fracture showed a transition of intergranular fracture→intergranular and transgranular mixed fracture→transgranular fracture. In the presence of hydrogen, the grain boundaries of elongated strips were prone to the formation of intergranular cracks under a tension load, and the hydrogen embrittlement resistance of the bulk lath bainite (LB) was weak. The hydrogen embrittlement susceptibility of pure granular bainite (GB) was lower. Fine LB and GB composite structures could remarkably inhibit intergranular cracks, giving the steel a superior resistance to hydrogen embrittlement.

Effects of the cementite morphology on the hydrogen trapping behavior in the pipeline steel

PurposeThe purpose of this study is to investigate the effects of the cementite morphology on the hydrogen trapping behavior in low-alloy pipeline steel.Design/methodology/approachIn this study, the hydrogen trapping behavior in low-alloy pipeline steel was quantitatively studied by a combination of microstructural observations, electrochemical hydrogen permeation experiments and thermal desorption spectroscopy (TDS) analyses.FindingsP-1 and P-2 steels are two samples with different microstructures. The morphology of cementite precipitates in the P-1 and P-2 steels was different. Lamellar cementite is present in P-2 steel and only granular cementite in P-1 steel, which led to a better irreversible hydrogen trapping ability of P-2 steel, which was confirmed by subsequent hydrogen permeation and TDS experiments.Originality/valueThe study of these deep hydrogen trap sites is helpful in improving the hydrogen embrittlement resistance of low-alloy pipeline steels.

The effect of Pd and Ni coatings on hydrogen permeation experiments of as-quenched martensitic steel

Abstract Hydrogen permeation technique is a widely used testing method for the determination of hydrogen diffusion coefficient (D), which is an important parameter considering hydrogen embrittlement. A palladium (Pd) or nickel (Ni) coating is often utilised on the hydrogen detection side of the test specimens. Here, we investigate the effect of Pd and Ni coatings on hydrogen diffusion in a martensitic 500 HBW hardness low-alloy steel in the thickness range of 0.5 – 0.8 mm using a refined successive transient method and compare against an uncoated reference specimen. Both coatings yield similar average D values (6 – 6.6 × 10−7 cm2/s), but the best repeatability is achieved with Pd coating. With Ni coating, D values decrease with the increasing specimen thickness, which is partly caused by a slower hydrogen diffusion in Ni, and therefore a concentration gradient at the specimen-coating interface. The uncoated specimen has a poor transient fit, and significantly lower D (2.1 × 10−7 cm2/s) due to surface oxidation. With both coatings, the steepness of the last decay transient was highly affected by specimen thickness, and therefore the density of reversible hydrogen traps is only comparable for similar thicknesses.

Hydrogen permeation and hydrogen damage behavior of high strength casing steel in acidic environment

To explore the effect of hydrogen permeation on pipes in an acidic environment, the tensile mechanical properties of three types of high strength steels were evaluated before and after hydrogen filling. The hydrogen damage behavior of three kinds of high-strength steels was studied by electrochemical hydrogen permeation test, MTS tensile test, and fracture morphology analysis. First, the basic physical and chemical properties of the materials were analyzed, and then the D-S double electrolytic cell technology was used for hydrogen permeation experiment. Finally, the influence of hydrogen loading on the tensile mechanical properties of the steel was determined by MTS tensile test and fracture morphology analysis. As the hydrogen filling current increases, the system temperature rises and the pH decreases, the hydrogen diffusion coefficient increases and the sensitivity of the steel to hydrogen embrittlement increases. The higher the steel strength, the higher the hydrogen diffusion coefficient, the higher the diffusible hydrogen concentration, the higher the hydrogen embrittlement sensitivity. The hydrogen damage evaluation method of high-strength steel used in this paper can provide a reference for the applicability evaluation of oil well pipe under acidic environment and provide theoretical guidance for the selection of oil well pipe in the field.

Effect of Cold Deformation on the Hydrogen Permeation Behavior of X65 Pipeline Steel

In this study, an electrochemical hydrogen permeation experiment was used to determine the diffusion parameters, and a hydrogen microprint test was used to visualize the distribution of hydrogen in X65 pipeline steel with different levels of cold deformation. The hydrogen permeation curves show that both hydrogen permeation current density and effective hydrogen diffusion coefficient decrease with increasing cold deformation. The density of reversible and irreversible hydrogen traps is calculated from the permeation parameters, and it is found that the amount of both traps increases with increasing deformation, especially a significant increase in reversible hydrogen traps, which is in agreement with the results measured by thermal desorption spectroscopy. Hydrogen microprint test results indicate that the degree of hydrogen aggregation on the specimen surface increases with increasing cold deformation, especially at phase and grain boundaries. In addition, the dislocation configuration after cold deformation was further investigated by transmission electron microscopy.

Effect of Mo Content on Hydrogen Evolution Reaction of 1400 MPa-Grade High-Strength Bolt Steel.

The effect of Mo content of 1400 MPa-grade high-strength bolt steel on hydrogen diffusion behavior and the hydrogen evolution reaction were studied using a hydrogen permeation experiment, potentiodynamic polarization tests, thermal desorption spectroscopy, and the first-principle calculation. Two 1400 MPa-grade high-strength bolt steels with different Mo content were used. Based on the potentiodynamic polarization tests, both steels' electrochemical behavior was similar in the test range. The hydrogen permeation experiment showed that the process of hydrogen adsorption and absorption was significantly promoted, and hydrogen desorption and recombination were slightly promoted, with the Mo content increasing from 0.70 to 1.09 wt%. The thermal desorption spectroscopy showed the overall reaction of hydrogen permeation and evolution. The increasing Mo content facilitated hydrogen entry behavior and increased the hydrogen content. According to the first-principle calculation and the density functional theory, this phenomenon is induced by the stronger bonding ability of Mo-H than Fe-H. This work could guide the design of 1400 MPa-grade high-strength bolt steel.

Hydrogen Embrittlement Susceptibility of Corrosion-Resistant Spring Rod Used in High-Speed Railway

The corrosion of spring steel is very important for vehicle safety. In this work, we conducted an experiment on multi-element micro-alloy composition design; the corrosion resistance of a 60Si2Mn spring was improved by adding Cr, Ni, Cu and other corrosion-resistant elements, and the corrosion resistance index (I) was increased from 3.21 to 8.62. Hydrogen embrittlement resistance was studied using a hydrogen permeation experiment and a slow strain rate tensile experiment. For this study, the following steps were performed: Firstly, the material composition was designed, and the experimental materials that met the experimental design were prepared according to the corresponding deformation and heat treatment process; secondly, the experimental materials were charged with hydrogen; and finally, conventional tensile testing, slow tensile testing and fracture morphology testing were carried out. A hydrogen permeation experiment was carried out for the materials. The result showed that, with the increase of hydrogen charging time, the hydrogen content of two steel samples increased, and the plasticity indexes such as elongation and reduction of the area appeared in three different stages which rapidly decreased, slowly declined, and then tended to balance. The uniform NbC nano precipitated phase can double the number of irreversible hydrogen traps (Nir) per unit volume, and decreased the effective hydrogen diffusion coefficient (Deff) from 1.135 × 10−10 to 6.036 × 10−11. It limited the free diffusion of hydrogen and made the immersed hydrogen harmless, thus improving the hydrogen embrittlement resistance of corrosion-resistant spring steel 60Si2Mn.

Study on the hydrogen barrier performance of the SiOC coating

SiOC coatings were prepared on X70 pipeline steel substrate by a simple dipping method at low temperatures, and their performance of hindering hydrogen penetration was studied through electrochemical hydrogen permeation experiment. The sample thermal-treated at 120 °C achieved a low diffusion coefficient of hydrogen of 8.20 × 10−9 cm2 s−1, which was nearly three orders of magnitude lower than 3.58 × 10−6 cm2 s−1 for the X70 steel. This was due to that the amorphous coating did not provide a stable hydrogen diffusion channel, thus limiting hydrogen diffusion. Density functional theory (DFT) calculation further proved that hydrogen moleculars were difficult to be adsorbed at different sites on the surface of the coating.

Research on hydrogen permeation in the X80 steel heat-affected zone with different heat inputs

Through electrochemical hydrogen permeation experiment at different hydrogen charging current densities, the hydrogen diffusion kinetic parameters such as penetration time tB , steady-state hydrogen permeation current density I ∞, hydrogen diffusion coefficient D, adsorbed hydrogen concentration C 0, hydrogen flux J, and hydrogen trap density NT in the heat-affected zone of X80 steel welding with different heat input were analyzed. The results show that the penetration time gradually decreases, and the I ∞ gradually increases with the increase of hydrogen charging current density. The penetration time of BM at the same hydrogen charging current density is the smallest, and the penetration times of CGHAZ specimens with different heat input conditions are relatively close. BM has the most significant hydrogen diffusion coefficient and negligible hydrogen trap density at the same hydrogen charging current densities. For CGHAZ, D significantly decreases and NT substantially increases, and there exists a threshold value that makes the lowest D in the CGHAZ with different heat inputs.

Effect of hydrogen traps on hydrogen permeation in X80 pipeline steel —— a joint experimental and modelling study

The permeation of hydrogen in the X80 steel was studied in this paper through thermal desorption spectroscopy, stepwise hydrogen permeation experiments and finite element modelling. Firstly, one kind of shallow trap and deep traps in X80 steel were identified through thermal desorption spectroscopy and the corresponding binding energies were obtained. According to the experiment and simulation, the deep hydrogen traps can significantly retard the first hydrogen permeation process but have almost no effect during the following charging. The X80 steel used in hydrogen compressed natural gas pipelines is exposed to hydrogen for long periods and deep traps are filled, its hydrogen permeation process is more in line with the stepwise hydrogen charging. Therefore, the stepwise hydrogen charging experiments were performed and the apparent diffusion coefficients (Dapp) and the hydrogen trap density involved in the hydrogen permeation transient (N1) were obtained using three different thickness samples. Then, a quantitative relationship in X80 steel was fitted between the N1 and the variation of hydrogen concentration. Based on the quantitative relationship and the hydrogen trap binding energies, a hydrogen permeation model in X80 steel was established. By comparing the hydrogen permeation curves obtained by our model under different boundary conditions with experiment curves, it is found that the constant concentration boundary condition model can better describe the hydrogen permeation kinetic in X80 steel under electrochemical hydrogen charging. As a result, this model can be used to predict the distribution of hydrogen in X80 steel, laying the foundation for predicting the occurrence of hydrogen embrittlement in pipeline steels.

Microstructure and Hydrogen Permeability of Nb-Ni-Ti-Zr-Co High Entropy Alloys.

Hydrogen separation membranes are one of the most promising technologies for hydrogen purification. The development of high-entropy alloys (HEAs) for hydrogen separation membranes is driven by a "cocktail effect" of elements with different hydrogen affinities to prevent hydride formation and retain high permeability due to the single-phase BCC structure. In this paper, equimolar and non-equimolar Nb-Ni-Ti-Zr-Co high entropy alloys were fabricated by arc melting. The microstructure and phase composition of the alloys were analyzed by scanning electron microscopy and X-ray diffraction, respectively. The hydrogen permeation experiments were performed at 300-500 °C and a hydrogen pressure of 4 bar. In order to estimate the effect of composition and lattice structure on hydrogen location and diffusivity in Nb-Ni-Ti-Zr-Co alloy, ab initio calculations of hydrogen binding energy were performed using virtual crystal approximation. It was found that Nb-enriched and near equimolar BCC phases were formed in Nb20Ni20Ti20Zr20Co20 HEA while Nb-enriched BCC and B2-Ni(Ti, Zr) were formed in Nb40Ni25Ti18Zr12Co5 alloy. Hydrogen permeability tests showed that Nb20Ni20Ti20Zr20Co20 HEA shows lower activation energy and higher permeability at lower temperatures as well as higher resistance to hydrogen embrittlement compared to Nb40Ni25Ti18Zr12Co5 alloy. The effect of composition, microstructure and hydrogen binding energies on permeability of the fabricated alloys was discussed.

Influence of hydrogen on the S–N fatigue of DP1180 advanced high-strength steel

We studied the load-controlled fatigue behaviour (at a stress ratio R = 0.1, 1 Hz, using smooth flat-sheet specimens) in air and with hydrogen (electrochemically charged at a current density of 16 mA cm−2 in 0.1 M NaOH) for a 1180 MPa dual-phase advanced high-strength steel. There was no significant difference between the fatigue lives with hydrogen and in air, even though there was a clear influence of hydrogen on the fatigue fractography. The hydrogen diffusion coefficient (0.8 ×10−6 cm2 s−1) and a hydrogen content of 1.0 µg g−1 were evaluated using hydrogen permeation experiments. A rougher surface produced a shorter fatigue life.