Hydrogen Permeation Rate Research Articles

Room Temperature Synthesis of Hydrogen Permeation Barrier for Storage and Transportation Application

Distribution of hydrogen in future hydrogen-based economy requires a dense pipeline network for its safe delivery. Natural take is to consider the existing networks of natural gas (NG) infrastructure. However, the main issue is that hydrogen-embrittlement on NG pipes’ steels significantly reduces their fracture toughness and threatens their structural integrity1. Besides developing a new grade of steels less susceptible to the embrittlement, effective hydrogen permeation barriers (HPBs) remain important solution for re-purposing of the existing NG infrastructure for hydrogen transport. Besides a few specific metals, candidates are some oxides,carbides, and nitrides. These coatings require extreme conditions for their synthesis, which renders their application impractical.We employed strategy for HPB synthesis based on electroless Cu-deposition process2. We have employ solution chemistries exploring a wide range of reducing agents. These include formaldehyde, glyoxylic acid, Na2HPO2 ... and others. Variety of complexing agents were considered as well; EDTA, sodium citrate, sodium potassium tartarate and others. Our optimum solution design favored a large driving force for Cu reduction providing high nucleation rates and films with fewer defects and dense grain boundaries. The comparative analysis between hydrogen permeation rates through bare steel samples and steel samples coated with Cu HPB films is performed using Devanathan - Stachurski permeation technique3. The Cu-HPB thickness varied from experiment to experiment. More than 30 samples have been evaluated. An integral example of these measurements is shown in Figure 1. Permeation reduction factor (PRF) for Cu-HPB as a function of the ratio between steel and Cu-HPB thickness is shown against theoretical calculations. Our results exceed theoretical predictions by factor of 2-5. Figure 1: Calculations for PRF of Cu/(AISI 4340 steel) as a function of ds/df ratio. Square, circular, and triangular dots represent PRF measurements for Cu-HPB/(ASTM A36 steel) samples produced from tartaric acid (TA) and EDTA solutions. Insets show optical images of steel and Cu/steel samples (left) and SEM of Cu surface morphology (right).

Experimental Study on Hydrogen Embrittlement Behavior of X80 and X70 Pipeline Steels Evaluated by Hydrogen Permeation and Slow Strain Rate Tensile Tests

Experimental Study on Hydrogen Embrittlement Behavior of X80 and X70 Pipeline Steels Evaluated by Hydrogen Permeation and Slow Strain Rate Tensile Tests

Nonlinear dynamics of a membrane reactor for hydrogen production: Multiplicity of equilibrium solutions and inhibition effects

Membrane reactors for the production of hydrogen are interesting devices that allow for the decentralized production of pure hydrogen while reducing the energy cost of the traditional steam reforming process. The performance of these systems is strongly dependent on the permeability and selectivity of the membrane employed for the separation of the produced hydrogen. Several studies have shown that the actual rate of hydrogen permeation is lower than the one that would be expected based on studies of membrane permeability carried out with pure hydrogen. This difference has been attributed to the competitive adsorption of other species, specifically CO, on the membrane surface. Here we show that this phenomenon could also lead to steady state multiplicity and analyze the dynamics of membrane reactors in the presence of competitive adsorption by CO. Emphasis has been placed on the effect of temperature and gas composition on possible multistable behavior. The results have been interpreted in terms of a transition between kinetics- and permeation-controlled regimes, in which the behavior of the reactor is limited, respectively, by the rate of the chemical reactions or the rate of hydrogen permeation.

Mechanism for Adsorption, Dissociation, and Diffusion of Hydrogen in High-Entropy Alloy AlCrTiNiV: First-Principles Calculation.

To investigate hydrogen behaviors in the high-entropy alloy AlCrTiNiV, density functional theory and transition state theory were used to explore the molecular H2 absorption and dissociation and the atomic H adsorption, diffusion, and penetration progress. The H2 molecule, where the H-H band is parallel to the surface layer, is more inclined to absorb on the top site of the Ti atom site of first atomic layer on the AlCrTiNiV surface, then diffuse into the hollow sites, through the bridge site, after dissociating into two H atoms. Atomic H is more likely to be absorbed on the hollow site. The absorption capacity for atomic H on the surface tends to decline with the increase in H coverage. By calculating the energy barriers of atomic H penetration in AlCrTiNiV, it was indicated that lattice distortion may be one important factor that impacts the permeation rate of hydrogen. Our theory research suggests that high-entropy alloys have potential for use as a hydrogen resistant coating material.

Mixed Potential Sensors for the Detection of Hydrogen Leaks from Geologic Reservoirs

Large-scale hydrogen (H2) geologic storage presents a viable alternative to surface storage that is both safer and more economical. One option being considered by DOE is H2 storage in salt formations. These formations have been successfully used for gas storage for decades due to their extremely low permeability and may see significant investment as the US ramps up its R&D efforts in this field. New Mexico has a unique advantage in that bedded salt formations are located strategically in areas where excess energy production can be harnessed for hydrogen production. However, bedded salt is more permeable than domal salt, necessitating sensor deployment to monitor H2 containment. Robust sensors that can provide early leakage detection will be an essential component of the safety of H2 operating facilities. In a LANL-funded Mission Foundations Research (MFR) project, we prepared several zirconia-based mixed potential hydrogen sensors utilizing a tin-doped indium oxide electrode for H2 leak detection to test its stability in subsurface environments. Previous electrochemical sensor work has shown this type of sensor in a hydrogen safety sensor role represents a significant improvement over currently available sensors as it has an extremely stable baseline and limited cross sensitivity to other gaseous compounds.1 The feasibility of this technology will be demonstrated through a hydrogen permeation experiment to measure rates of underground hydrogen permeation between boreholes drilled underground at the DOE Waste Isolation Pilot Plant (WIPP) site. This experiment will (1) establish the use of this novel sensor in geologic H2 storage applications and (2) investigate the feasibility of H2 storage in bedded rock salt. Acknowledgement This research is supported by the Los Alamos National Laboratory, Laboratory Directed Research and Development (LDRD) Office, Missions Foundation Research Charter (Debora Wagner Program Manager). References E. L. Brosha, C. J. Romero, D. Poppe, T. L. Williamson, C. R. Kreller, R. Mukundan, R. S. Glass, and A. S. Wu, “Field Trials Testing of Mixed Potential Electrochemical Hydrogen Safety Sensors at Commercial California Hydrogen Filling Stations,” Journal of the Electrochemical Society 164 (13) B681-B689 (2017).

Strategies for Reducing the Ohmic Resistance in a Proton Exchange Membrane Electrolysis Cell

Ohmic polarization caused by the contact resistance between components and their own bulk resistance is the main polarization loss in proton exchange membrane electrolysis cells. To investigate this, we adopted an electrolysis cell with an active area of 25 cm2 and explored methods of reducing ohmic resistance. First, two kinds of polar plate were designed to investigate the contact area between transport layer and catalytic layer. The results showed that the polar plate with the higher ridge area made the transport layer and catalytic layer achieve good contact, resulting in an ohmic resistance decreases of 17.5 mΩ cm2 when the contact area increases from 16.85 to 21.6 cm2. Second, Pt coating was used to prevent oxidation of the titanium felt and improve electrolytic performance. Sputtering titanium felt exhibits the best performance with the electrolysis voltage of 1.814 V at 2 A cm−2. Finally, we studied different proton exchange membranes and analyzed the performance and hydrogen permeation rate with the self-made membrane electrode, finding that the electrolytic voltage of the Solvay E98–05 S reaches 1.733 V at 2 A cm−2 due to the minimum thickness and the highest conductivity, and the H2 permeation current density is only 2.184 mA cm−2.

Cathode Catalyst Layer Design in PEM Water Electrolysis toward Reduced Pt Loading and Hydrogen Crossover.

Reducing the use of platinum group metals is crucial for the large-scale deployment of proton exchange membrane (PEM) water electrolysis systems. The optimization of the cathode catalyst layer and decrease of the cathode Pt loading are usually overlooked due to the predominant focus of research on the anode. However, given the close relationship between the rate of hydrogen permeation through the membrane in an operating cell and the local hydrogen concentration near the membrane-cathode interface, the structural design of the cathode catalyst layer is considered to be of pivotal importance for reducing H2 crossover, particularly in combination with the use of thin (≲50 μm) membranes. In this study, we have conducted a detailed investigation on the cathode structural parameters, covering the Pt wt % of the Pt/C electrocatalyst, the type of carbon support (Vulcan and high surface area carbon, HSAC), and the ionomer content, with a goal to reduce Pt loading to 0.025 mgPt/cm2 while minimizing the rate of cell hydrogen crossover. We found that the electrochemical performance is mainly influenced by the changes in the interfacial contact resistance due to variations in the cathode thickness. Both the Pt wt % in Pt/C and the ionomer content showed a positive correlation with the measured H2 in O2% in the anode outlet, whereas the Pt loading exhibited an opposite trend. The rate of hydrogen crossover was analyzed in relation to the calculated local volumetric current density within the cathode catalyst layer. Based on the obtained hydrogen mass transfer coefficient, a cathode catalyst layer comprising 40 wt % Pt on HSAC support with an ionomer-to-carbon (I/C) ratio of 0.35 was found to be an optimum configuration for achieving a low Pt loading of 0.025 mgPt/cm2 and a reduced rate of hydrogen crossover.

A CFD model of natural gas steam reforming in a catalytic membrane reactor: Effect of various operating parameters on the performance of CMR

The use of hydrogen as an energy carrier has increased for reasons related to its environmentally friendly characteristics. The most common and low-cost method of producing hydrogen from natural gas (or CH4) is the steam reforming process. The 2-D axisymmetric catalytic membrane reactor (CMR) model is developed for pure hydrogen production from real natural gas (NG) using a Pd–Ru membrane with a Ni/Al2O3 catalyst. In this paper, a CFD model is prepared to investigate the performance of a catalytic membrane reactor through natural gas conversion and hydrogen production under various operation parameters, i.e., temperature of reaction in the range of 600, 700, 800, 900, and 1000 K, gas hourly space velocity GHSV with a range of 500, 700, 1000, 2000, and 3000 h−1, and sweep gas flow rate (Re No.) 1, 50, 100, 150, and 250. The results of the simulation show that the CMR exhibits a high permeation rate of hydrogen on the permeate side (tube side) and achieves a high methane conversion rate of approximately 99.9 % at 1000 K on the retentate side. The hydrogen flux exhibits a decline as the temperature increases from 900 to 1000 K, despite the achievement of complete (NG) conversion. Hence, it can be concluded that the performance of the catalytic membrane reactor (CMR) process exhibits a pattern of increase when the other parameters, such as (GHSV) and (Re.No.), are increased.

Enhancing Durability of Polymer Electrolyte Membrane Water Electrolyzer through Incorporation of Gas Recombination Catalyst in Membrane

Hydrogen will become a critical component of the future energy landscape driven primarily by the growing use of renewable energy sources. Polymer electrolyte membrane water electrolyzer (PEMWE) is a superior technology to facilitate hydrogen production from renewable electricity. However, durability remains a significant challenge for the widespread commercialization of electrolyzers.1 Cross-over of H2 from cathode to anode could lead to explosive mixtures in the anode causing safety concerns during operation. Hydrogen crossover also impacts the durability of the anode catalyst.2 Hydrogen permeation from the cathode to the anode through the membrane reduces the anodic Ir catalyst to a low valence state leading to increased dissolution of the Ir catalyst at a high cell voltage. Utilizing thin membranes (~50µm) can improve the electrolyzer system’s efficiency but also increase the hydrogen permeation, particularly at high pressures.In this study, we present a methodology to incorporate platinum as a gas recombination catalyst (GRC) layer into commercial membranes, significantly reducing hydrogen permeation rates and mitigating anode catalyst degradation. Membranes with GRC can mitigate the degradation of PEMWE, leading to more efficient and durable PEM electrolysis systems for hydrogen production. The methodology developed enables higher control of the GRC layer properties (Pt particle size and location in the membrane). Ex-situ measurement of hydrogen permeation, shown in Figure 1, indicates a significant reduction in the permeation rate for GRC incorporated NR 212. This study presents a systematic electrochemical evaluation of anode degradation in PEMWE with and without GRC in the membrane using accelerated stress tests. The durability of the GRC during long-term operation is also presented. Acknowledgment This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office through the Hydrogen from Next-generation Electrolyzers of Water (H2NEW) consortium.

Hydrogen Embrittlement Susceptibility of Ti-6Al-4V Alloys Fabricated by Electron Beam Melting in Simulated Deep-Sea Environment

The hydrogen embrittlement susceptibility of electron beam melted Ti-6Al-4V alloy (ET) was compared with that of conventional wrought alloy (WT). Hydrogen permeation, electrochemical, and slow strain rate tensile tests as well as surface observation were conducted under a simulated sea environment. The results show that the hydrogen embrittlement susceptibility of ET is lower than that of WT, which can be attributed to the intense texture of ET with a smaller specific surface area of grain boundary, preventing hydrogen permeation. Moreover, with increasing depth of the ocean, the hydrogen embrittlement susceptibility of both ET and WT TC4 alloys increases considerably. This reduced hydrogen embrittlement resistance can be attributed to the degradation of the passivation film, accelerating the permeation flux of hydrogen.

Thin Films of a Complex Polymer Compound for the Inhibition of Iron Alloy Corrosion in a H3PO4 Solution.

The etching of iron alloy items in a H3PO4 solution is used in various human activities (gas and oil production, metalworking, transport, utilities, etc.). The etching of iron alloys is associated with significant material losses due to their corrosion. It has been found that an efficient way to prevent the corrosion of iron alloys in a H3PO4 solution involves the formation of thin complex compound films consisting of the corrosion inhibitor molecules of a triazole derivative (TrzD) on their surface. It has been shown that the protection of iron alloys with a mixture of TrzD + KNCS in a H3PO4 solution is accompanied by the formation of a thin film of coordination polymer compounds thicker than 4 nm consisting of TrzD molecules, Fe2+ cations and NCS-. The layer of the complex compound immediately adjacent to the iron alloy surface is chemisorbed on it. The efficiency of this composition as an inhibitor of iron alloy corrosion and hydrogen bulk sorption by iron alloys is determined by its ability to form a coordination polymer compound layer, as experimentally confirmed by electrochemical, AFM and XPS data. The efficiency values of inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C6H12N4 at a temperature of 20 ± 1 °C are 97% and 98%, respectively. The kinetic parameters of the limiting processes of hydrogen evolution and permeation into an iron alloy in a H3PO4 solution were determined. A significant decrease in both the reaction rate of hydrogen evolution and the rate of hydrogen permeation into the iron alloy by the TrzD and its mixtures in question was noted. The inhibitor compositions 5 mM TrzD + 0.5 mM KNCS and 5 mM TrzD + 0.5 mM KNCS + 200 mM C6H12N4 decreased the total hydrogen concentration in the iron alloy up to 9.3- and 11-fold, respectively. The preservation of the iron alloy plasticity in the corrosive environment containing the inhibitor under study was determined by a decrease in the hydrogen content in the alloy bulk.

(Invited) Lowering the Noble Metal Requirement for PEM Water Electrolysis: Membrane Electrode Assembly and Porous Transport Layer Design Considerations

The Net Zero Emission scenario proposed by the International Energy Agency projects a required electrolytic generation of hydrogen equivalent to 3600 GW by 2050 [1], averaging to an annual installation of ~130 GW/a between 2023 and 2050. If this were to be provided by proton exchange membrane based water electrolyzers (PEM-WEs) based on platinum catalysts for the hydrogen evolution reaction (HER) and iridium catalysts for the oxygen evolution reaction (OER), the current PEM-WE noble metal requirements of ~0.7 gIr/kW and ~0.3 gPt/kW [1] would have to be drastically reduced in view of the noble metal supply constraints. As argued previously, for PEM-WEs to be sustainable on such a large scale would require to achieve platinum and iridium loadings of ~0.05 mg/cm2 electrode [2,3]. While the former can be easily achieved due to the fast HER kinetics on Pt, the latter requires either ultra-thin OER catalyst layers or improved OER catalysts with a substantially reduced iridium packing density (in units of gIr/cm3 electrode) [2], like the recently developed catalyst with a hydrous iridium oxide shell supported on a titanium oxide core (IrOx/TiO2) [4,5].In this contribution, we will discuss the effect of the design of membrane electrode assemblies (MEAs) and of the adjacent porous transport layers on PEM-WE performance. In general, the preparation of MEAs with low platinum loading cathodes is straightforward, due to the availability of carbon supported platinum catalysts (Pt/C) with a low Pt packing density. For the optimization of the ionomer content in the cathode electrode, however, its effect on the high current density performance and on the hydrogen permeation rate from cathode to anode have to be considered [6,7].With regards to the anode electrode, we will further discuss the MEA design challenges when targeting ultra-low iridium loadings. In the case of the ultra-thin catalyst layers that result when using conventional OER catalysts, additional contact resistances between the anode catalyst layer and the titanium based porous transport layer (Ti-PTL) are observed [2]. As will be shown, these can be largely mitigated by the use of a titanium based microporous layer (MPL) coated on the Ti-PTL, highlighting the importance of the interface between the PTL and the anode catalyst layer. In case of using the above described IrOx/TiO2 catalysts with low iridium packing density, their typically lower electrical conductivity also results in apparent contact resistances within and across the anode catalyst layer [4], which poses an additional constraint on the allowable range of the catalyst/ionomer ratio in the anode electrode. The interplay between the anode catalyst type, the anode ionomer content, and the type of interface between the anode electrode and the PTL (i.e., with and without MPL) will be discussed.

Influence of Frictional Heat on Hydrogen Permeation Measurements

Hydrogen transport properties in metals are often investigated in electrochemical Devanathan-Stachurski double cells (DS) or modifications thereof. A DS setup consists of input and output cells which are divided by a metal membrane. The hydrogen oxidation current measured in the output cell is proportional to the permeation rate of hydrogen through the metal membrane. In certain applications of lubricated tribocontacts, steel is susceptible to damages by uptake of hydrogen. For investigation of the friction-generated hydrogen uptake a lubricated sliding contact in the input cell of the DS setup is realized.Related low hydrogen permeation current signals are significantly affected by the steel membrane temperature. As an example, frictional heating of the steel membrane leads to additional release of residual hydrogen from the steel. To investigate the temperature effect, tests with an oil containing a hydrogen promotor, a PFPE oil and without lubrication were conducted. The results indicate that the permeation signal is strongly influenced by frictional heating. Such measured currents must not be misinterpreted as hydrogen generated by lubricants. A thermodynamic and kinetic model of the hydrogen diffusion and trapping reveals the correlation between current signal and temperature change.

Effect of a PTL Coating and the Clamping Pressure on the Performance of a PEM Electrolyzer Cell

The temperature of the earth is slowly increasing due to the excess CO2 production from the use of fossil fuels in the energy consumption and power production cycles. By 2050, The IEA has devised the net zero energy plan to allow the hydrogen use to extend to several parts of the energy sectors and grow to meet 10% of total final energy consumption by that year [1]. A key player in the decarbonization plan is electrolysis technology. Specifically, PEM electrolysis has gained popularity throughout the years and has started to become more commercialized and its coupling to renewables allowed the technology to produce fully green hydrogen. Researchers’ goal now is to optimize this technology and reduce its cost. As it uses a protonic membrane in an acidic media, it requires expensive components that need to sustain harsh acidic conditions[2].Usually, a PEM water electrolysis unit is made up of a CCM (catalyst coated membrane made with a Nafion 115 coated with iridium oxide on the anode side and nanoparticles of platinum on a carbon support on the cathode side) sandwiched between a titanium porous layer at the anode and a carbon GDL on the cathode. All the components are contained with feeding plates usually made from titanium[3]. The electrolyzer is tightened enough to prevent leaks and ensure a good contact resistance. However, too much clamping can damage the components of the cell as it can reduce the GDL porosity, furthermore can reduce the protonic conductivity of the membrane due to the decreasing of its water content; hence limiting the electrolyzer performance. Another effect is the thinning of the membrane which can affect the hydrogen permeation rate and possibly cause a safety issue as the hydrogen in oxygen content should be less than 2%[4]. Each component has its influence on the contact resistance, the most influential one is that between the porous titanium PTL and the anodic catalytic layer. One uncoated PTL and three coated PTLs (Au, Pt, Ir) where implemented. The precious metal deposit has a positive effect on the interfacial contact resistance between the catalyst layer and the PTL as it decreases compared to an uncoated PTL: the gain is about 150mV at 2A/cm² for a 6.6 MPa clamping pressure – see Fig. 1a. The three deposits lead to the same performances below 2.5A/cm2 and for higher current densities the Iridium deposit is less good than the gold and platinum ones at the beginning of life. After an activation of few hundred hours of operation, the iridium deposit leads to the same performance as the platinum deposit and the gold deposit began to dissolve. To explore higher clamping pressure, the carbon GDL was replaced by a more rigid titanium felt and clamping experiment with an uncoated PTL were performed from 2.9 to 13.22MPa – see figure 1.b. Then decreasing it to see the effect of excessive tightening and relaxation, but unexpected increase in performance was observed up until a certain clamping (6.6MPa) (Fig. 1b) during the relaxation phase then the performances started to decrease. We attribute this behavior to the better water absorption of the membrane during the relaxation phase once the electrical contact is achieved at high pressures. These results might show an efficient method in assembly and clamping of an electrolyzer cell to obtain better performances.[1] F. Dolci, Fuel Cells and Hydrogen Joint Undertaking - Programme review report 2017. 2018.[2] D. G. Bessarabov and P. Millet, PEM water electrolysis. 2017.[3] M. Sánchez-Molina, E. Amores, N. Rojas, and M. Kunowsky, “Additive manufacturing of bipolar plates for hydrogen production in proton exchange membrane water electrolysis cells,” Int. J. Hydrogen Energy, vol. 46, no. 79, pp. 38983–38991, 2021, doi: 10.1016/j.ijhydene.2021.09.152.[4] T. J. Mason, J. Millichamp, P. R. Shearing, and D. J. L. Brett, “A study of the effect of compression on the performance of polymer electrolyte fuel cells using electrochemical impedance spectroscopy and dimensional change analysis,” Int. J. Hydrogen Energy, vol. 38, no. 18, pp. 7414–7422, 2013, doi: 10.1016/j.ijhydene.2013.04.021. Figure 1

Thin 1,2,4-Triazole Films for the Inhibition of Carbon Steel Corrosion in Sulfuric Acid Solution

Etching of steel items in sulfuric acid solution is used in various human activities (oil and gas industry, metal production, utilities, transport, etc.). This operation is associated with significant material costs due to corrosion losses of the metal. It has been found that an efficient way to prevent corrosion of steel in sulfuric acid solution involves the formation of thin protective films consisting of corrosion inhibitor molecules of triazole class on its surface. It has been shown that the protection of steels with a 3-substituted 1,2,4-triazole (3ST) in H2SO4 solution is accompanied by the formation of a polymolecular layer up to 4 nm thick. The 3ST layer immediately adjacent to the steel surface is chemisorbed on it. The efficiency of this compound as an inhibitor of corrosion and hydrogen absorption by steel is determined by its ability to form a protective organic layer, as experimentally confirmed by XPS and AFM data. The kinetic constants of the main stages of hydrogen evolution and permeation into steel in the H2SO4 solution were determined. A significant decrease in both the reaction rate of cathodic hydrogen evolution and the rate of hydrogen permeation into steel by the triazole in question was noted. It has been shown that the preservation of the metal plasticity in the acid medium containing the triazole under study is due to a decrease in the hydrogen concentration in the metal bulk.

Effect of Temperature and H Flux on the NH3 Synthesis via Electrochemical Hydrogen Permeation.

Ammonia is an indispensable commodity and a potential carbon free energy carrier. The use of H permeable electrodes to synthesize ammonia from N2 , water and electricity, provides a promising alternative to the fossil fuel based Haber-Bosch process. Here, H permeable Ni electrodes are investigated in the operating temperature range 25-120 °C, and varying the rate of electrochemical atomic hydrogen permeation. At 120 °C, a steady reaction is achieved for over 12 h with 10 times higher cumulative NH3 production and almost 40-fold increase in faradaic efficiency compared to room temperature experiments. NH3 is formed with a cell potential of 1.4 V, corresponding to a minimum electrical energy investment of 6.6 kWh kg-1 . The stable operation is attributed to a balanced control over the population of N, NHx and H species at the catalyst surface. These findings extend the understanding on the mechanisms involved in the nitrogen reduction reaction and may facilitate the development of an efficient green ammonia synthesis process.

Investigation of steam methane reforming in a Pd–Ru membrane reactor with a counter-current configuration

Steam methane reforming (SMR) in a membrane reactor is a promising method to continuously produce high-purity hydrogen, which can directly supply to the proton exchange membrane fuel cell without complex CO purification processes. The performance of SMR in a Pd–Ru membrane reactor with a counter-current configuration for various operation parameters is investigated numerically in this work. In particular, the reverse hydrogen permeation is analyzed. The enhancement in the methane conversion by increasing the sweep ratio is ineffective for high sweep ratios. The hydrogen permeation rate increases with the membrane length, but the average hydrogen permeation flux decreases. The reverse permeation length increases with membrane length and feed gas flow rate. However, it decreases with sweep ratio and temperature. Replacing the membrane with the non-permeation material in the reverse permeate region achieves higher performance with less membrane area.

Characteristics of hydrogen separation and methane steam reforming in a Pd-based membrane reactor of shell and tube design

This work investigates numerically the characteristics of the two process, hydrogen separation and steam methane reforming (SMR), in a palladium-based (Inconel-supported Pd–Ag film) membrane reactor (MR) of porous reformer (30% Ni/Al2O3) shell and multi-tube design. Still parameters like reactor design and temperature, feed gas concentration and pressure, and flow configuration need more investigation to figure out their impact on hydrogen production rate at lower energy cost and minimum possible volume. This work targets optimization of reactor performance for higher hydrogen yield and coming up with a scalable optimized reactor design for industrial applications. First, an optimization study is performed under non-reforming (separation-only) conditions to optimize the MR design and operating parameters for higher hydrogen production. Then, the study is extended to consider hydrogen separation under SMR conditions to come up with a MR design for hydrogen production at the industrial scale. Hydrogen permeation is limited to small zone near the membrane surface with no effect of feed pressure, inlet gas temperature, and feed hydrogen concentration on widening such zone that necessitates reducing the pitch distance between membrane tubes below 22 mm. The results showed reduced hydrogen permeation rate under SMR conditions compared to the separation-only cases.

Effects of Applied Cathodic Current on Hydrogen Infusion, Embrittlement, and Corrosion-Induced Hydrogen Embrittlement Behaviors of Ultra-High Strength Steel for Automotive Applications

The effects of the electrogalvanizing conditions (a combination of plating current and time) on hydrogen infusion, embrittlement, and corrosion-induced hydrogen embrittlement (HE) behaviors of ultra-high strength steel were examined. A range of experimental and analytical methods, including electrochemical impedance spectroscopy, hydrogen permeation, polarization, and slow strain rate test, were employed. The results showed that the applied cathodic current density during electrogalvanizing had an inverse relationship with the Zn crystalline size. A smaller cathodic current density and longer plating time led to a larger crystalline size, resulting in a higher infusion rate of hydrogen atoms, and HE-sensitivity (i.e., mechanical degradation with larger density of secondary crack in fracture surface). On the other hand, a larger cathodic current density and shorter plating time caused a higher anodic dissolution rate and smaller polarization resistance of the coating when exposed to neutral aqueous environments. Hence, a higher rate of galvanic corrosion between the coating and exposed steel substrate (e.g., locally damaged areas around coating layer) resulted in a higher infusion rate of hydrogen atoms and HE-sensitivity. This study provides insight into the desirable plating conditions for electro-Zn plating on ultra-high strength steels with enhanced resistance to hydrogen infusion and embrittlement, induced by aqueous corrosion.

Study on hydrogen embrittlement susceptibility of X80 steel through in-situ gaseous hydrogen permeation and slow strain rate tensile tests

Hydrogen embrittlement is a serious threat to the safety operation for hydrogen blended natural gas pipelines. To determine the critical safety hydrogen blending ratio, in-situ high-pressure gaseous hydrogen permeation tests and slow strain rate tensile tests of X80 pipeline steel were conducted in the simulated hydrogen blended natural gas environments with 0–20 vol% hydrogen. The permeability characteristics, mechanical properties and fracture morphologies were systematically analyzed, and the embrittlement mechanism was discussed. Results show that the subsurface hydrogen concentration, ductility loss and hydrogen embrittlement susceptibility increased significantly as hydrogen blending ratio increased from 10% to 15%. Moreover, a positive correlation between subsurface hydrogen concentration and hydrogen embrittlement index was revealed. Combining the gaseous hydrogen permeation, SSRT results and fracture analysis, the 10% hydrogen blending ratio was determined as the conservative critical value for the safety operation of X80 hydrogen blended natural gas pipelines.