Hydrogen Charging Research Articles

Reconstruction of Electric Double Layer for Long‐Life Aqueous Zinc Metal Batteries

AbstractAqueous rechargeable Zn metal batteries (AZMBs) have attracted widespread attention due to their intrinsic high volumetric capacity and low cost. However, the unstable Zn/electrolyte interface causes Zn dendrite growth and side reactions, resulting in poor Coulombic efficiency and unsatisfactory lifespan. Herein, a SiO2 reinforced‐sodium alginate (SA) hybrid film is designed to regulate solid–liquid interaction energy and spatial distribution of all species in the electric double layer (EDL) near the Zn electrode. The unique interfacial layer gives rise to a uniform distribution of Zn2+ in the Helmholtz layer through solvation sheath modulation. Moreover, theoretical calculations show that the SO42− anions and free‐water are substantially reduced in the Helmholtz layer, effectively suppressing hydrogen evolution reaction and formation of by‐products through strong charge repulsion and hydrogen bond fixing of free‐water. The reconfigured EDL not only ensures homogenous and fast Zn2+ transport kinetics for dendrite‐free Zn deposition, but also eliminates interface parasitic side reactions. The Zn@SiO2‐SA electrode enables excellent cycling stability of symmetrical cells and high‐loading full AZMBs with a lifespan over 3000 h and an areal capacity of 2.05 mAh cm−2, thus laying a solid basis for realizing practical AZMBs.

Influence of stress triaxiality on hydrogen assisted ductile damage in an X70 pipeline steel

The presence of hydrogen in steel components affects their structural integrity through a phenomenon called hydrogen embrittlement. While it is known that hydrogen affects the mechanical damage development upon loading, the specific mechanisms are still unclear. An experimental study is presented that investigates the plastic anisotropy and ductile fracture behavior of API 5L X70 pipeline steel with and without hydrogen charging at multiple scales. Three different tensile test specimen geometries (smooth and notched axisymmetric) are employed to investigate the influence of stress triaxiality thereon. The macromechanical responses during tensile tests are analyzed, along with micromechanical features of the resulting damage obtained using High-Resolution X-ray Computed Tomography. For all stress triaxialities tested, the presence of hydrogen does not affect the macroscopic plastic anisotropy, but accelerates ductile damage development and fracture, which is in agreement with the plasticity dominated hydrogen embrittlement mechanisms HELP and HESIV. Increasing stress triaxiality leads to a larger susceptibility to hydrogen embrittlement. Hydrogen accelerated void nucleation and enhanced lateral void growth are observed and quantified. The presented results can aid the development of numerical models describing hydrogen embrittlement in high-strength low-alloy steel.

Temperature-Dependent Hydrogen Embrittlement of Austenitic Stainless Steel on Phase Transformation

A critical issue that needs to be addressed for wider utilization of hydrogen as fuel is protection against hydrogen embrittlement during cryogenic storage as it weakens the microstructure bonding force of metals through hydrogen penetration. Austenitic stainless steel, which is usually used in cryogenic vessels and is well known for its high hydrogen resistance at room temperature, has also been reported to be vulnerable to hydrogen embrittlement under cryogenic temperatures. In addition, because large storage vessels are operated over a wide range of temperatures, material behavior at various temperature conditions should also be considered. Therefore, in the present study, hydrogen charging of austenitic stainless steel was performed under various temperature conditions for carrying out prestrain and tensile tests. A decrease in the tensile strength and elongation and an increase in the yield strength were observed in all cases. In particular, the case of 20% prestrain at cryogenic temperature followed by tensile test at room temperature after hydrogen charging showed fracture in the elastic region. The hydrogen index was evaluated from the perspective of elongation and reduction in area, which are factors that indicate the degree of ductility. The aforementioned case showed the most severe results, while non-prestraining followed by tensile tests at room temperature was the least effected by hydrogen. In addition, the effect of strain-induced martensite on hydrogen embrittlement was analyzed using electron backscattered diffraction (EBSD). It was observed that the higher is the prestrain at cryogenic temperatures, the greater is the volume fraction of α’ martensite, which leads to hydrogen embrittlement. The edges and center of the fracture surface were analyzed using scanning electron microscopy (SEM). The hydrogen-charged specimens exhibited brittle fractures at the edges and ductile fractures at the center. The more severe the embrittlement, the more were the number of intergranular fractures and microdimples observed at the edges.

The effect of copper coated metal hydride at different ratios on the reaction kinetics

In this study, the process parameters that affect the improvement of hydrogen storage material properties were investigated. In order to accelerate the hydrogen charge/discharge processes and to obtain the required hydrogen at the desired flow rates in a short time, the thermal conductivity of the storage materials has been improved, and density analyses have been made. The ideal grinding time has been determined for the LaNi5 material. Within the scope of the experimental studies, the thermal conductivity coefficients of LaNi5 coated with copper and LaNi5 ground for 5 h and coated with copper were increased by 500–750%, and the copper plating ratios were optimized. The materials obtained were characterized by XRD, SEM, and their density was measured with the Helium Pyknometer device and their thermal conductivity coefficients with the Hot Disk Thermal Constants Analyzer. In addition, the hydrogen storage of materials with increased thermal conductivity was investigated experimentally in the metal hydride reactor at the determined pressure. In the study, it was seen that the storage material coated with copper increases the heat transfer, reduces the hydrogen charging time in the metal hydride reactor, and increases the stable discharge time.

Digital Image Correlation Technique to Aid Monotonic and Cyclic Testing in a Noisy Environment during In Situ Electrochemical Hydrogen Charging

Hydrogen is receiving growing interest as an energy carrier to facilitate the shift to a green economy. However, hydrogen may cause the significant degradation of mechanical properties of structural materials, premature strain localisation, crack nucleation, and catastrophic fracture. Therefore, mechanical testing in hydrogenating conditions plays a vital role in material integrity assessment. Digital image correlation (DIC) is a versatile optical technique that is ideally suited for studying local deformation distribution under external stimuli. However, during mechanical testing with in situ electrochemical hydrogen charging, gas bubbles inherent to hydrogen recombination are created at the sample surface, causing significant errors in the DIC measurements, and posing significant challenges to researchers and practitioners utilising this technique for testing in harsh environments. A postprocessing technique for the digital removal of gas bubbles is presented and validated for severe charging conditions (−1400 mV vs. Ag/AgCl) under monotonic and cyclic loading conditions. Displacement fields and strain measurements are produced from the filtered images. An example application for measuring the crack tip opening displacement during a slow strain rate tensile test is presented. The limitations of the technique and a comparison to other bubble mitigation techniques are briefly discussed. It was concluded that the proposed filtering technique is highly effective in the digital removal of gas bubbles during in situ electrochemical hydrogen charging, enabling the use of DIC when the sample surface is almost completely obscured by gas bubbles.

The Metallurgical hydrogen as an indicator and cause of damage to rolled steel: Hydrogen diagnostics of fracture

Fatigue tests and measurements of the volumetric distribution of metallurgical hydrogen in specimens cut from rolled I-beam 60Sh3 made of steel 10KhSND were carried out. Fatigue tests show a 20% reduction in fatigue limits compared to similar sheet material. On the fractures of the samples, there are flock-like defects in the areas of interface of the flanges of the I-beam, or the so-called zones of difficult deformation. The concentration of metallurgical hydrogen is unevenly distributed and varies from 0.17 ppm to 1.8 ppm. Large concentrations of hydrogen are observed in the zones of difficult deformation, which indicates the hydrogen nature of the metal defects observed at the fracture. The result of mechanical tests and hydrogen diagnostics is a manufacturing defect of rolled products that cannot be corrected. Hydrogen diagnostics using metallurgical hydrogen (without hydrogen charging samples) takes tens of times less time than mechanical tests, and gives an adequate result.

Effects of grain boundary character distribution on hydrogen-induced cracks initiation and propagation at different strain rates in a nickel-saving and high-nitrogen austenitic stainless steel

The effect of grain boundary character distribution (GBCD) on hydrogen-induced cracks (HICs) initiation and propagation in nickel-saving austenitic stainless steel was investigated at different strain rates with electrochemical hydrogen charging. The fracture strength and elongation of specimens decreased as the strain rates decreased due to more hydrogen atoms being transported by mobile dislocations. HICs are more likely to initiate at random grain boundaries (RGBs) because of poor deformation coordination of adjacent grains at RGBs after hydrogen charging. Special boundaries (SBs) deflected HICs and hindered the propagation of HICs owing to a more stable boundary structure and less strain localization during slow strain rate tensile (SSRT) deformation with hydrogen charging. Furthermore, highly efficient distributions of SBs contribute to great resistance to hydrogen embrittlement.

Boosting the hydrogen storage performance of MgH2 by Vanadium based complex oxides

MgH2, a solid-state hydrogen storage material with high storage capacity, is facing the obstacles of high thermodynamic stability and slow reaction kinetics. Herein, different Vanadium (V) based catalysts (V2O5, Fe–V and V–Ni oxides) were synthesized by a hydrothermal method and ball milled with MgH2 to modify its hydrogen storage property. It is observed that the dehydrogenation performance (initial dehydrogenation temperature and desorption rate) of Fe–V oxide doped MgH2 was the best, followed by V2O5 and V–Ni oxide modified systems. The MgH2+7 wt% Fe–V composite exhibited an onset dehydrogenation temperature of 200 °C, 128 °C lower compared with the original MgH2. The absorption performance of MgH2 was also greatly enhanced by Fe–V oxide. The 7 wt% Fe–V modified MgH2 after dehydrogenation began to charge hydrogen from 25 °C to 5.1 wt% hydrogen was absorbed at 150 °C. The activation energy for hydrogen uptake of MgH2 was reduced from 76.5 ± 3.4 kJ/mol to 41.2 ± 4.7 kJ/mol. Additionally, the MgH2+7 wt% Fe–V composite maintained 97.2% hydrogen capacity after10 cycles. Our work here proves that elements substitution is a feasible way to tune the catalytic effect of oxides and may shed light on designing catalysts with higher activation in the future.

Hydrogen embrittlement behavior in the nugget zone of friction stir welded X100 pipeline steel

Hydrogen-induced damage is an inevitable challenge in pipeline safety applications, especially, the fusion welded joints owing to microstructure heterogeneity caused by welding process. In this work, X100 pipeline steel was subjected to friction stir welding (FSW) at rotation rates of 300–600 rpm under water cooling, and the relationship among the microstructure, hydrogen diffusivity, and hydrogen embrittlement (HE) behavior of the nugget zone (NZ) were studied. The NZ at 600 rpm had the highest effective hydrogen diffusion coefficient (Deff) of 2.1 × 10−10 m2/s because of the highest dislocation density and lowest ratio of effective grain boundary. The Deff decreased with decreasing rotation rate due to the decrease of dislocation density and the increase of ratio of effective grain boundary, and the lowest Deff of 1.32 × 10−10 m2/s was obtained at 300 rpm. After hydrogen charging, the tensile strength of all specimens decreased slightly, while the elongation decreased significantly. As the rotation rate decreased, the elongation loss was obviously inhibited, and ultimately a lowest elongation loss of 31.8% was obtained at 300 rpm. The abovementioned excellent mechanical properties were attributed to the fine ferrite/martensite structure, low Deff, and strong {111}//ND texture dramatically inhibiting hydrogen-induced cracking initiation and propagation.

Mechanical loading effect on the hydrogen uptake of tempered martensite steel: Elastic strain effect vs. plastic strain effect

The effects of mechanical loading on hydrogen uptake were investigated by thermal desorption experiments under various combinations of hydrogen charging and loading conditions. The diffusible hydrogen content increased with increasing elastic and plastic strains. The increase in diffusible hydrogen content per elastic strain was larger than that per plastic strain.

1T-phase MoS2/holey ultrathin g-C3N4 nanosheets based 2D/2D heterostructure for enhanced photocatalytic hydrogen production

Although graphitic carbon nitride (g-C3N4) is widely used for photocatalytic hydrogen production, its practical application is restricted by the high recombination rate of photoinduced electron-hole pairs and limited active sites. In this work, holey ultrathin g-C3N4 nanosheets (HCN NSs) with rich active sites are prepared, followed by the growth of 1T-MoS2 NSs on their surfaces to construct 2D/2D 1T-MoS2/HCN heterostructure. Due to the high surface area and abundant hydrogen active sites of the hybrid, large and intimate 2D nanointerface between MoS2 and HCN, hydrogen ion adsorption and charge separation/transport ability are greatly enhanced. As a result, 1T-MoS2/HCN-4 with the optimal 1T-MoS2 content of 8 wt% displays the highest H2 production rate of 2724.2 μmol−1 h−1 g−1 under simulated solar light illumination with apparent quantum efficiency of 8.1% (λ = 370 nm). Moreover, the 1T-MoS2/HCN-4 hybrid manifests improved stability after a long-time test. This study opens the door to design highly-efficient g-C3N4 based 2D/2D heterostructures for photocatalytic H2 production.

Rare‐Earth Doping Transitional Metal Phosphide for Efficient Hydrogen Evolution in Natural Seawater

Electrolysis of inexhaustible seawater offers a promising way for harvesting practically infinite hydrogen energy without worsening freshwater shortage. Complicated ionic environment of saline seawater, however, places a great burden on catalyst performance for hydrogen evolution. Herein, tailoring the electronic structure of transitional metal phosphide by rare‐earth doping for effectively propelling hydrogen evolution in a wide pH range and natural seawater is reported. The rare‐earth doping leads to not only a nearly zero Gibbs free energy of H* adsorption and lower work function but also faster OH* desorption for rapid release of the active sites, thereby accelerating the hydrogen evolution reaction (HER) kinetics under nonacidic conditions. On this basis, highly conductive and hydrophilic MXene is introduced to further boost the adsorption of hydrogen carriers and charge transfer across the catalyst. Together, they allow the activity, kinetics, and durability of the electrocatalyst for HER to be improved overall. The obtained electrocatalyst shows superior activity to commercial Pt/C in terms of specific surface area and active mass and turnover frequency, as well as 400 times longer lifetime than Pt/C with high Faradaic efficiency in natural seawater. This study presents new insight into the development of viable electrocatalysts for harvesting hydrogen energy from abundant‐reserve seawater.

Critical verification of the effective diffusion concept

Knowing the hydrogen distribution c(x,t) and local hydrogen concentration gradients grad(c) in ferritic steel components is crucial with respect to hydrogen embrittlement. Basically, hydrogen is absorbed from corrosive or gaseous environments via the surface and diffuses through interstitial lattice sites into bulk. Although, the lattice diffusion coefficient DL∼0.01mm2/s is in the order of magnitude of those for well-annealed pure iron, trapping sites in the microstructure retard the long-range chemical diffusion jL=−Dchem(c)grad(c), causing local hydrogen accumulation in near surface regions in limited time. Considering pure ferritic crystals without trapping sites in the microstructure, the limited characteristic diffusion depth xc∼Defft is proportional to the square root of the effective diffusion coefficient Deff and of time t. Effective diffusion coefficients are measured independently for hydrogen using the electrochemical permeation technique. For pure crystals, the effective diffusion coefficient is constant at given temperature and allows accurate calculations of the diffusion depths. However, with trapping sites in the microstructure the effective diffusion coefficient is not a material property anymore and becomes dependent on the hydrogen charging conditions. In the present work, the theory of hydrogen bulk diffusion is used to verify the concept of effective diffusion. For that purpose, the generalized bulk diffusion equation was solved numerically by using the finite difference method (FDM). The implementation was checked using analytical solutions and a comprehensive convergence study was done to avoid mesh and time dependency of the results. It is shown that effective diffusion coefficients can vary by magnitudes depending on the sub-surface lattice concentration. This limits the application of the effective diffusion concept and also the calculation of the characteristic diffusion depth.

Graphite Nanoflake-Modified Mo2C with Ameliorated Interfacial Interaction as an Electrocatalyst for Hydrogen Evolution Reaction.

Molybdenum carbide (Mo2C) is anticipated to be a promising electrocatalyst for electrocatalytic hydrogen production due to its low cost, resourceful property, prominent stability, and Pt-like electrocatalytic activity. The rational design of Mo2C-based electrocatalysts is expected to improve hydrogen evolution reaction (HER) performance, especially by constructing ultrasmall Mo2C particles and appropriate interfaces. Herein, composites of molybdenum carbide (Mo2C) quantum dots anchored on graphite nanoflakes (Mo2C/G) were fabricated, which realized a stable overpotential of 136 mV at 10 mA cm-2 for the HER with a small Tafel slope of 76.81 mV dec-1 in alkaline media, and operated stably over 10 h and 2000 cycles. The superior HER performance can be attributed to the fact that graphite nanoflakes could act as a matrix to disperse Mo2C as quantum dots to expose more active sites and guarantee high electronic conductivity and, more importantly, provide ameliorated interfacial interaction between Mo2C and graphite nanoflakes with appropriate hydrogen binding energy and charge density distribution. To further explore which kind of interfacial interaction is more favorable to improve the HER performance, density functional theory calculations and corresponding contrast experiments were also performed, and it was interesting to prove that Mo2C quantum dots anchored to the basal planes of defective graphite nanoflakes exhibit better electrochemical performance than those anchored on the edges.

Efficient Visible‐Light‐Initiated Dehydrogenative Coupling of Amines for Coproduction of Imines and Hydrogen over NiS/ZnIn2S4

NiS is deposited on the surface of hexagonal ZnIn2S4 via a hydrothermal method and the as‐obtained NiS/ZnIn2S4 nanocomposite shows superior activity for photocatalytic dehydrogenative coupling of amines to produce imines, with simultaneous generation of hydrogen under visible light. The superior performance over NiS/ZnIn2S4 for photocatalytic dehydrogenative coupling of benzylamine to produce N‐benzylidenebenzylamine can not only be ascribed to NiS, which acts as a cocatalyst to promote the charge transfer and hydrogen evolution, but also attributed to its strong adsorption toward benzylamine and its relatively weak adsorption toward the product, which is also proved by density functional theory calculations. This study not only provides an efficient, green, and cost‐effective strategy to produce imines, but also demonstrates that the adsorption of the photocatalyst toward the reactants and the products is an important issue that should be considered in a photocatalytic reaction.

Activation energy study on nanostructured niobium substituted Mg2Ni intermetallic alloy for hydrogen storage application

The magnesium-based metallic alloys have been exhibited to be the improved hydrogen storage materials. In the present investigation, a nanostructured Mg67Ni33 and Niobium substituted intermetallic compound was prepared by a high-energy ball milling technique for hydrogen storage application. Niobium substitution on the pure crystalline intermetallic compound changed the structure of the crystalline to semi-amorphous as well as changed the interplanar spacing after 30 h of milling. Furthermore, the effect of Nb substitution on the inter-planar shift and its corresponding implications on lattice strain, crystallite size, and unit cell volume of the Mg2Ni compound were also discussed. Transmission electron microscope studies confirm the particle size was reduced to less than 100 nm for 30 h of milling. However, SEM images confirm the agglomeration of these nanoparticles and form spherical particles of size around 3–5 μm. XRD and EDS authenticate the presence of oxides. Kissinger’s analysis confirmed that Mg2Ni powder exhibited lower activation energy of 64.101 kJ mol−1 than niobium-substituted alloy powders. The hydrogen charge and discharge potential of these compounds are discussed in detail.

Mechanism of hydrogen-induced defects and cracking in Ti and Ti–Mo alloy

Mechanism of Hydrogen-induced defects and cracking in Ti and Ti–Mo alloy was systematically analyzed from the perspective of microstructure. Results show that more hydrogen atoms can be dissolved in Ti–Mo alloy due to the existence of β phase, and the precipitation amount of hydride is reduced under the same hydrogen charging conditions. The analysis of positron annihilation results show that the solid solution of Mo element reduces the hydrogen induced defect concentration in the alloy and inhibit the combination of hydrogen and defects. At the same time, Mo atom can affect the electronic structure of Titanium hydrides, and then reduce the bonding between titanium atoms and hydrogen atoms, thereby reducing the formation of brittle titanium hydride. The reduction of hydride and hydrogen induced defect concentration significantly decrease the hardening rate of Ti–Mo alloy, thereby effectively reducing the hydrogen embrittlement sensitivity of titanium and inhibiting its hydrogen absorption cracking tendency.

Experimental analysis of hydrogen storage performance of a LaNi5–H2 reactor with phase change materials

Energy storage, especially thermal energy storage, has an important place in terms of efficient use of energy. Systems in which phase change materials (PCMs) are used are among the thermal energy storage (TES) options, thanks to their advantages such as energy storage at almost constant temperature. The use of PCM as a TES material in the metal hydride (MH) reactor is an influential method to store the heat released by the exothermic reaction occurring in the hydrogen charging process and to recover this heat with the endothermic reaction occurring in the hydrogen discharge process. In the present study, hydrogen charge and discharge processes in a LaNi5–H2 reactor were experimentally investigated and compared with and without PCM. Therefore, a hybrid system was designed by integrating PCM around the cylindrical MH reactor filled with LaNi5 alloy. The hydration process was carried out at both constant pressure and variable pressure. The temperature changes on the reactor surface and inside the PCM were measured over time. In experiments to determine the change in the amount of hydrogen stored in MH reactors over time, it was determined that the hydrogen storage pressure and reactor design significantly affect the hydrogen charge-discharge rate. Considering the use of MH reactors in transportation vehicles such as automobiles and submarines, designing a hybrid MH-PCM storage system is promising for the development of hydrogen storage technologies and transportation technologies.

1D growth of Cr-rich nanophase induced by hydrogen in high-entropy alloy AlCoCrFeNi2.1

• Body-centered cubic phase in cast AlCoCrFeNi 2.1 contains lots of Cr-rich nanophases. • During the hydrogenation process, excess dislocations and vacancies are generated. • Dislocation pile-up and lattice misfit at the phase boundaries favor Cr-segregation. • Hydrogen-induced Cr-segregation near nanophase leads to its one-dimensional growth. One-dimensional (1D) growth of dense Cr-rich nanophase was found in the body-centered cubic (BCC) phase of the eutectic dual-phase high-entropy alloy (HEA) AlCoCrFeNi 2.1 after hydrogen charging (AHC). H atoms diffuse faster and deeper in the BCC, resulting in abundant vacancies and dislocations. The plentiful nanophase particles in the BCC phase before hydrogen charging (BHC) provide nucleation sites for its growth. Cr atoms diffuse faster under the complex interaction of dislocations, vacancies, and H atoms. Furthermore, the dislocations pinned by the nanophase lead to Cr atoms attached to the nanophase segregation. The 1D growth of nanophase shows two growth modes: island-chain fiber and habit-plane whisker.

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.