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Membrane processes are energy‐saving and promising for the purification of hydrogen, which is critical to clean energy supply and carbon capture. Developing high‐performance separation membranes is of great scientific and practical interest. In this study, a concept of using mesoporous graphene oxide (MGO) nanosheets to guide nanoconfined growth of low‐crystallinity metal‐organic framework (LCM) membranes for precise gas sieving is reported. By utilization of nanowire‐electrochemical perforation and oxidation for GO, the MGO nanosheets are reconstructed with in‐plane mesopores and abundant reactive groups and can provide nanoconfinement effects of limiting reaction region, offering anchoring sites, changing precursor diffusion, and squeezing crystallization, for in situ growth of amorphous LCM layers between adjacent mesoporous nanosheets. Benefiting from ultrathin, defect‐free, low‐crystallinity, and robust properties, combined with reduced tortuosity of MGO and adjusted transport pathways of LCM, the MGO/LCM membranes exhibit substantially enhanced long‐term stability, moisture resistance, and separation capability, with high H2/CO2 selectivity of 104 and ultrafast H2 permeance of ≈4000 gas permeation units, which can surpass those of most state‐of‐the‐art membranes. [ABSTRACT FROM AUTHOR]

Solar thermochemical hydrogen production is a promising pathway for producing sustainable fuels and chemicals. One of the main challenges in the development of these processes is their low steam conversion extent, dictated by its restrictive thermodynamics requiring extremely high temperatures over 1500 °C and low oxygen partial pressure to obtain a steam conversion over 10%. While condensing the unreacted steam is technically simple, the latent heat is thus rendered useless for the process. In many cases, this lost heat can be larger than the higher heating value of the produced hydrogen. We propose a new separation method based on a mechanical vapor recompression cycle, enabling the recovery of the latent heat by compressing the steam–hydrogen mixture prior to the condensation process, thus creating a temperature difference between the hot exhaust and cold inlet streams. We show that this separation method can recover the latent heat and keep its quality in relevant operating conditions while requiring less than 14% of the recovered heat for compression work, resulting in a coefficient of performance over 7. This method increases the viability of solar thermochemical hydrogen production cycles, especially under limited steam conversion conditions. • A new method for hydrogen–steam separation based on mechanical vapor recompression. • Coefficient of performance can achieve value over 10 for low steam conversion cases. • At higher conversion additional heat is needed to complete the boiling of the fresh steam. • Applications in solar thermochemical hydrogen production can increase overall system efficiency. [ABSTRACT FROM AUTHOR]

The separation of high-purity hydrogen from mixed gasses using dense metallic alloy membranes is essential for advancing a hydrogen-based economy. Palladium-based membranes exhibit outstanding catalytic activity and theoretically infinite hydrogen selectivity, but their high cost and limited performance in contaminant-rich environments restrict their widespread use. This study addresses these limitations by exploring strategies to develop cost-effective, high-performance alternatives. Key challenges include the vast compositional design space, lack of systematic design principles, and the slow pace of traditional material development. This review emphasizes the potential of high-throughput and combinatorial techniques, such as composition-spread alloy films and the statistical design of experiments (DoE), combined with machine learning and materials informatics, to accelerate the discovery, optimization, and characterization of palladium-based membranes. These approaches reduce development time and costs while improving efficiency. Focusing on critical properties such as surface catalytic activity, resistance to chemical and physical stresses, and the incorporation of low-cost base metals, this study introduces domain-specific descriptors to address data scarcity and improve material screening. By integrating computational and experimental methods, future research can identify hidden material correlations and expedite the rational design of next-generation hydrogen separation membranes. [ABSTRACT FROM AUTHOR]

Fossil fuels provide over 80% of the world's current energy demand, which results in the release of large amounts of greenhouse gases (GHGs). In contrast to the emissions of GHGs caused by the combustion of fossil fuels, hydrogen combustion produces only water as a waste product. Hydrogen is a more environmentally friendly alternative fuel. The production of hydrogen energy has the potential to address energy security issues such as climate change and air pollution. There is an increasing global interest in hydrogen, particularly green hydrogen, which is produced by electrolyzing water using power derived from renewable resources. Because of falling hydrogen prices and the growing urgency of decarbonization, global demand for hydrogen, headed by the transportation and industrial sectors, might increase by about 400% by 2050. Furthermore, using environmentally friendly hydrogen will result in a reduction of 3.6 gigatonnes of total carbon dioxide emissions between 2020 and 2050. Hydrogen has the highest energy density of any known fuel, and it is widely available in enormous quantities all over the planet. It is possible that by 2050, India's need for hydrogen will have increased by a factor of 4, accounting for more than 10% of global consumption. Steel and heavy-duty transportation are expected to account for more than 52% of overall demand growth between now and 2050. The overall market value for environmentally friendly hydrogen in India might reach $8 billion by 2030 and $340 billion by 2050. Because India's capacity to create power from renewable sources is growing all the time, the country now can produce hydrogen from ecologically beneficial sources such as solar and wind when demand is low. Physical adsorption and polymer membranes can be employed to extract hydrogen from crude hydrogen polluted with hydrocarbons. This can be done to clean the crude hydrogen. The purity of hydrogen is an important aspect in determining whether it can be used in the energy production process. Unlike other types of separation technologies, membrane processes can be used in both mobile and small-scale applications. The membrane may function properly under a wide range of pressure and temperature extremes. The fundamental objective and goal of the separation membrane is to be used in membrane reactors for synchronous hydrogen production and purification. Other competing methods, such as pressure swing adsorption and cryogenic distillation, do not compare favorably to the membrane separation approach at lower operating temperatures. This is because membrane separation takes fewer resources than other competing technologies, particularly ones that have been around for a longer time. This article discusses the various membranes that can be used for substance separation, how hydrogen separation membranes can be made using a variety of technologies, the challenges that are inherent in doing so, and the prospects for the future, particularly in terms of increasing the efficiency of hydrogen separation. [ABSTRACT FROM AUTHOR]

Membrane gas separation is an environmentally friendly and economical method used to separate valuable gases, industrial process gas wastes, and carbon dioxide from mixed gases. The most important part of this method is the membranes. Gas separation membranes are expected to have high separation and permeability performance, high mechanical strength, easy and fast production capability, and low prices. Polymer-based membranes are mostly preferred depending on the ease of modification capability. In this study, a zirconium-based metal organic framework (Zr-MOF, MIL-140 A) was synthesized and used as a filler within polyvinyl alcohol (PVA) matrix for the selective separation of hydrogen (H2) from carbon dioxide (CO2). The effect of MIL-140 A addition on the mechanical, structural, and morphological properties of PVA was evaluated. The MIL-140 A significantly improved the mechanical strength of the membrane. According to the gas separation results, the increasing concentration of MIL-140 A increased the selective separation performance of the nanocomposite membrane. The highest mechanical strength (43.1 MPa) and best film-forming ability were obtained with 3 wt% MIL-140 A loaded membrane. The ideal H2/CO2 selectivity and hydrogen permeability were obtained as 5.6 and 944 Barrer, respectively at 2 bar feed pressure and room temperature. The highest ideal H2/CO2 selectivity was obtained as 6.3 with the H2 permeability of 959 Barrer when the MIL-140 A ratio was 4 wt%. [ABSTRACT FROM AUTHOR]

Metal-based membranes have emerged as a promising solution, providing selective permeability and impressive durability. However, a comprehensive understanding of their environmental performance across their entire life cycle remains elusive. This research offers a comprehensive life cycle assessment (LCA) of electroless plated palladium alloy-based membranes for hydrogen separation. It evaluates the environmental impacts across various stages, from the synthesis of supports to the application of intermediate and selective layers. Key findings include the identification of alumina supports and graphite intermediate layers as having minimal environmental impacts, and the Pd–Cu membrane as the most sustainable choice among palladium alloy membranes. This research advances our understanding of the eco-friendly performance of palladium based H 2 separation membranes, guiding the development of more sustainable hydrogen separation technologies. [Display omitted] • Environmental comparison of support, intermediate, and selective layers in metal-based H 2 separation membranes. • Use of the Electroless Plating method. • Alumina supports have the least environmental impact. • Graphite layers offer the lowest comprehensive environmental effects across various categories for the intermediate layers. • Pd–Cu membrane is the most sustainable choice in Pd alloy membranes due to its minimal environmental impact. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) production and demand have steadily increased, leading to a rise in carbon dioxide (CO2) emissions since fossil fuels are the current raw material for H2 production. Thin film composite (TFC) hollow fiber membranes have become significant in H2 purification and CO2 capture, playing a critical role in developing next-generation fuels and supporting the United Nations Sustainable Development Goal 7 (SDG 7) – Affordable and Clean Energy, with the goal of providing universal access to clean, advanced, and renewable energy for all. However, the polymeric selective layer of TFC membranes faces a trade-off between permeability and selectivity, as well as challenges including CO2 plasticization and physical aging. Additionally, H2/CO2 separation remains particularly challenging because H2, being diffusivity-selective, permeates more quickly through the membrane due to its smaller molecular size and higher kinetic energy, while CO2, being solubility-selective, has a high affinity for dissolving in most polymeric membranes. Herein, this review provides an in-depth exploration of innovative modification strategies designed to overcome these challenges in glassy polymeric membranes and enhance H2 separation performance in the recent 10 years. Various nanofillers, such as metal-organic frameworks (MOFs) such as University of Oslo (UiO), Materials Institute Lavoisier (MILs), and Zeolitic Imidazolate Frameworks (ZIFs), have shown remarkable potential in boosting gas separation capabilities due to their superior compatibility with polymer matrices and tunable properties. The review also explores different types of hollow fiber membranes, including single layer, dual-layer, and TFC, alongside fabrication techniques like interfacial polymerization and dip-coating. Critically, the analysis highlights cutting-edge strategies to improve membrane performance, such as (i) thermal cross-linking, (ii) chemical cross-linking, (iii) ultraviolet (UV) cross-linking, (iv) polymer blends, and (v) modified fillers, along with their objectives and expected outcome. Furthermore, the review spotlights breakthroughs in H2/CO2, H2/CH4, and H2/N2 separation technologies, emphasizing the critical need for continued innovation to drive sustainable H2 production and meet the growing clean energy demand.

In this research, cobalt-doped silica membranes were synthesized using the sol-gel method. The properties of the membrane support are of great importance for selective membrane coating. Membrane support permeability and surface roughness are two important and measurable characteristics in support selection. Therefore, two types of modified supports were selected for this study; the first support with a surface roughness of 160 nm and an average hydrogen permeance of about 5.5 × 10-7 mol m-2 s-1 Pa-1, and the second support with a surface roughness of 54 nm and an average hydrogen permeance of 3.5 × 10-6 mol m-2 s-1 Pa-1 were used. The cobalt-doped silica layer was uniformly coated on both supports, and molecular sieve activity was observed in both membranes permeation. The results show that utilizing a modified support with low surface roughness and high permeance resulted in a cobalt-doped silica membrane with pure hydrogen permeance of 1.3 × 10⁻⁷ mol m-2 s-1 Pa-1 and average ideal selectivity of 40 and 25 for H₂/N₂ and H₂/CO₂, respectively, at 150°C. Conversely, the cobalt-doped silica membrane on the modified support with high surface roughness and low permeability exhibited significantly weaker performance with pure hydrogen permeance of 1.6 × 10-9 mol m-2 s-1 Pa-1 and average ideal selectivity of 16 and 13 for H₂/N₂ and H₂/CO₂, respectively, at the same temperature. The findings demonstrate the appropriateness of the sol-gel process for producing cobalt-doped silica membranes that are selective, but they also emphasize how important it is for the support surface's roughness and permeance to affect the membrane's performance. [ABSTRACT FROM AUTHOR]

Hydrogen is a carbon-free fuel and can be expected to play a significant role in the global clean energy transition. In this study, two proposed small-scale hydrogen production plant configurations were designed and simulated for high-purity hydrogen production at a rate of 25 kg H2 /day. The feasibility and economic viability of the proposed plant configurations were examined. Additionally, the performance and sensitivity analysis were assessed under different operating conditions. Configuration A proposed to use two reactors for ammonia cracking and H 2 separation, respectively. Configuration B considers that the decomposition of ammonia and H 2 separation simultaneously occurs in a single integrated reactor. Despite the configuration B was more energy efficient than configuration A but both configurations are applicable. The total H 2 production cost of configuration A was 6.39 $/kg H2 and that of configuration B was 6.06 $/kg H2. Since the proposed plant configurations generated both hydrogen and nitrogen, the total cost of production was distributed between them. Therefore, the final H 2 and N 2 separation costs of configuration A was 5.05 $/kg H2 and 1.14 $/kg N2 , and configuration B was 4.72 $/kg H2 and 1.08 $/kg N2. The hydrogen production cost from different ammonia synthesis pathways was compared. The technology readiness level (TRL) for hydrogen production from ammonia cracking was assessed and identified at a range of TRL 4–6. It can also be considered that the ammonia synthesis pathway controlled the ammonia prices and subsequently the hydrogen production cost. • Two proposed configurations were designed for H 2 production from blue NH 3. • Techno-economic assessment was performed for small-scale H 2 plants. • The final H 2 cost of proposed configuration A was higher than configuration B. • The H 2 production cost from different NH 3 synthesis pathways was also compared. • The pathway of NH 3 synthesis influenced the prices of NH 3 and H 2. [ABSTRACT FROM AUTHOR]

Nanoparticles can suppress asymmetric precursor support collapse during pyrolysis to create carbon molecular sieve (CMS) membranes. This advance allows elimination of standard sol‐gel support stabilization steps. Here we report a simple but surprisingly important thermal soaking step at 400 °C in the pyrolysis process to obtain high performance CMS membranes. The composite CMS membranes show CO2/CH4 (50 : 50) mixed gas feed with an attractive CO2/CH4 selectivity of 134.2 and CO2 permeance of 71 GPU at 35 °C. Furthermore, a H2/CH4 selectivity of 663 with H2 permeance of 240 GPU was achieved for promising green energy resource‐H2 separation processes. [ABSTRACT FROM AUTHOR]

Pd membrane on porous Al 2 O 3 , an important composite membrane for H 2 separation, is typically fabricated by electroless plating, and thus the quality of the Pd membrane is critically dependent on the seeding process. Here, a facile ultrasonication-assisted sensitization-activation process is used to load catalytic particles on porous Al 2 O 3 , subsequently followed by electroless plating of 5-μm-thick Pd membranes for H 2 separation. Uniformly distributed catalytic particles with even sizes are loaded onto Al 2 O 3 only under an optimal power of the ultrasonic agitation, then catalyzing electroless Pd membranes with a better surface topography and less defective microstructure. The optimal Pd membrane achieves a sound hydrogen flux of 0.157 mol m−2 s−1 and high H 2 /N 2 selectivity of 1835 under 723 K and 105 kPa pressure difference. Moreover, this particular Pd/Al 2 O 3 exhibits high stability in (a) Pd membrane microstructures and (b) H 2 /N 2 permeating fluxes without elemental interfacial diffusion even under long-term (156 h) at a high temperature (723 K). [Display omitted] • Ultrasonic- and magnetic-agitations are used to load Pd(Sn) seeds on porous Al 2 O 3. • High-quality electroless Pd membrane is obtained on the ultrasonically-seeded Al 2 O 3. • Mechanisms of defect-related N 2 /H 2 permeation for Pd-coated Al 2 O 3 are studied. • Ultrasonically-seeded Pd membranes exhibit high selectivity and long-term durability. • The long-term durability is related to sturdiness of Pd membrane and Al 2 O 3 support. [ABSTRACT FROM AUTHOR]

Hydrogen separation using nanostructured membranes has gained research attention because of its potential to produce high‐purity hydrogen by separating gases at the molecular level. Quadrupole mass spectrometry (QMS) is one method to evaluate these membranes' effectiveness in separating hydrogen from gas mixtures. However, quantifying gases in a mixture with QMS is challenging, especially when heavier gas ions interfere with a light gas ion, resulting in lower quantification accuracy. This study addresses this challenge by presenting a detailed calibration procedure that significantly improves hydrogen quantification accuracy up to a factor of 2.5. CO and CO2 were chosen as interfering gases because they are commonly released in conventional hydrogen production processes. By carefully evaluating the performance of these membranes, new opportunities for hydrogen separation may be realized. [ABSTRACT FROM AUTHOR]

The influence of vacuum pressure applied on H2 separation from a palladium membrane is explored in this study. Three factors with three levels are considered, including the membrane chamber temperature with levels 320 °C, 350 °C, and 380 °C; the retentate-side total pressure with levels 1, 2, and 3 atm; and the permeation-side vacuum pressure with levels 0, 25, and 50 kPa. The Taguchi, response surface methodology (RSM), and multivariate adaptive regression splines (MARS) methods are employed to analyze the effects of the three parameters on hydrogen separation and predict their optimal combination. The retentate-side total pressure exhibits the highest impact on H2 permeation, following the permeation-side vacuum pressure and then the membrane chamber temperature. The maximum H2 flux is 0.226 mol∙s−1∙m−2, with H2 recovery of 91 % obtained at the optimal conditions with a temperature of 380 °C, a total pressure of 3 atm, and a vacuum pressure of 50 kPa. The improvement in H2 flux reaches 21.6 % compared with the case without the imposed vacuum pressure at the same temperature and total pressure. This result shows the imposed vacuum pressure is an efficient way to enhance H2 permeation. The maximum relative errors between the experimental data and the predictions from the Taguchi, RSM, and MARS methods are 6.74 %, 3.37 %, and 8.08 %, respectively. The RSM method presents higher accuracy than Taguchi and MARS, perhaps due to a more precise analysis of the interaction terms. The smaller amount of input data and ignoring the temperature effect in MARS could be the reason for the lower accuracy. Nevertheless, the MARS method still demonstrates acceptable results. The cost of the Taguchi method is lower than that of the RSM method since it requires fewer experimental cases. In a word, the choice of the prediction method depends on the desired accuracy and the experimental cost.

Depleting energy resources, global warming and environmental problems associated with conventional fuels are serious global challenges of the modern world. The substitution of conventional energy resources with more efficient and sustainable resources is inevitable. In this scenario, hydrogen (H2) has emerged as the ultimate choice due to its superior characteristics such as low carbon emissions, cleanliness, and efficiency. However, for the successful implementation of making H2as the next-generation fuel source, the hurdles of production, separation, and storage of H2should be resolved. This paper summarizes the issues and challenges in the separation of H2gas from various production streams by using available separation technologies. Different types of H2separation technologies, including membranes, adsorption processes, metal hydrides, and cryogenic separation technologies, have been considered and discussed. The review encompasses the types, advantages, and disadvantages of each technology, followed by a detailed account of issues and challenges observed in each separation method. More attention has been given to membrane technology because it is the most promising technology for the production of high-purity H2. Finally, this review provides an outlook for future directions and developments in H2separation technologies.

Experimental findings to contribute to the preliminary design of a metal foil pump for fuel separation in the Direct Internal Recycling loop of the DEMO fusion device are presented. In parametric studies on a small-scale superpermeation experiment with a microwave plasma source and two different metal foil materials, niobium Nb and vanadium V, a substantial increase in permeation with plasma power and with a decrease in pressure was observed. To ease operation in the typical fusion environment, in-situ heating procedures were developed to recover from impurity contamination. The temperature independence of plasma-driven permeation from 600 to 900 °C metal foil temperature was demonstrated. No proof of an isotopic effect for plasma-driven permeation of protium and deuterium could be found. The highest repeatable permeation flux achieved was 6.7 Pa∙m3/(m2∙s) or ~5.5 × 10−3 mol H/(m2∙s). The found compression ratios do safely allow the operation of the metal foil pump using ejector pumps as backing stages for the permeate. In a dedicated experimental setup, the operation of the plasma source in a strong magnetic field was tested. Parametric studies of pressure, power input, magnetic flux density, field gradient and field angle are presented.

In this study, we have reported a new strategy to prepare metal/ceramic membranes that can be used as an alternative to conventional high-cost palladium membranes. For the first time, a uniform Ni layer was deposited using the organic-inorganic activation method via the ELP technique. Although, alloying Pd–Ni resulted in a defect-free thin membrane layer (2 μm). The H 2 permeation flux of the composite membrane was 1.43 × 10−2 mol m−2 s−1 at 450 °C and TMP of 100 kPa with infinite H 2 /N 2 selectivity. Stage cut effect as a function of transmembrane pressure (TMP) was assessed in binary mixtures at 450 °C. The prepared composite membrane indicated perfect long-time permeance stability for 145 h at 450 °C and TMP of 100–300 kPa. The results showed that solution-diffusion is the dominant mechanism in the hydrogen transport through the composite membranes. [Display omitted] • A uniform Ni layer was deposited using the organic-inorganic activation method. • Knudsen diffusion governed hydrogen transport in the Ni composite membrane. • Alloying Pd–Ni results in a defect-free membrane layer with infinite H 2 /N 2 selectivity. • The Pd–Ni composite membrane showed perfect permeance stability over 145 h at 450 °C. • Solution-diffusion governed hydrogen transport in the Pd–Ni composite membrane. [ABSTRACT FROM AUTHOR]

This work reports the performance of Mixed Matrix Membranes (MMMs) for hydrogen purification. ZIF-8 and ZIF-90 Zeolitic Imidazole Frameworks (ZIFs) have been used as additives to improve the separation performance of the pristine Matrimid® polymeric membrane. The good interfacial contact and distribution of the filler along the membrane have been determined by electronic microscopy and the comparison of the membrane's performance is done in terms of hydrogen permeability and selectivity from industrial waste streams. The results showed that MMMs almost double H 2 permeability (50 Barrer) and increase H 2 selectivity (H 2 /CO 2 : ≈4.3, H 2 /N 2 : ≈35, H 2 /CO: ≈41, H 2 /CH 4 : ≈36) compared to the pristine polymeric membrane. Finally, the influence of the feed composition (by means of binary and multicomponent mixtures) and temperature (30, 50 and 80 °C) as operating variables has been analysed. The permeability was stable in the wide range of feed compositions while the increase in temperature resulted in lower selectivity and higher permeability. [Display omitted] • Matrimid®/ZIF membranes have been prepared for hydrogen separation. • The membranes have been tested with synthetic gas mixtures (COG, MPG, APG). • The Matrimid®/ZIF membranes double the H 2 permeability (50 Barrer) of Matrimid®. [ABSTRACT FROM AUTHOR]

VB-group-based ternary alloys membranes for hydrogen separation have attracted great attention because of their superiorities on selectivity and permeability of hydrogen. However, atomic-scale hydrogen separation properties of the ternary alloys are still not studied, further related study is critical for developing high-performance V–Ni-based alloys membranes. In this work, molecular dynamics (MD) and first-principles calculation are incorporated to predict performances of V–Ni–Al, V–Ni–Fe and V–Ni–Co ternary alloys for separation of H 2 from N 2 , CO 2 , CO, CH 4 , H 2 O and H 2 S mixed gases. Based on calculations of adsorption properties, diffusion energy barrier, selectivity and charge density difference, it reveals that the alloys membranes show excellent permeance and selectivity for separation of hydrogen gas. In particular, V–Ni–Al membrane presents superior diffusion and permeability properties for hydrogen gas. Our calculations provide an insight into atomic-level mechanism of V–Ni–Al, V–Ni–Fe and V–Ni–Co alloys as high-performance hydrogen separation membranes. [Display omitted] • For the first time, H 2 selectivity and permeance of V–Ni ternary alloy is studied. • The predicted gas separation properties are consistent with experimental results. • Permeance of V–Ni–Al to H 2 is much greater than those of V–Ni–Co and V–Ni–Fe. • H 2 permeance exceeds industrial production limit above room temperature. • Our approach can be used to evaluate gas separation performance of ternary alloys. [ABSTRACT FROM AUTHOR]

In order to improve the properties, alkaline earth element doped La 1.95 M 0.05 Hf 2 O 7-δ (M = Ca, Sr, Ba) are prepared by high-temperature solid state method. The experimental results indicate that Ca is a suitable doping element. The prepared La 2-x Ca x Hf 2 O 7-δ (x = 0, 0.025, 0.05, 0.1) series samples are of pure pyrochlore structures. Among them, La 1.95 Ca 0.05 Hf 2 O 7-δ has the densest structure, the highest conductivity, which is 2.86 × 10−3 S cm−1 in humid air at 800 °C, and outstanding chemical stability in H 2 O, CO 2 , H 2 and 300 ppm H 2 S. The hydrogen separation performance of La 1.95 Ca 0.05 Hf 2 O 7-δ membrane is tested using the external short-circuit method. The hydrogen permeation flux of 1.25 mm thick La 1.95 Ca 0.05 Hf 2 O 7-δ membrane is 0.15 mL·min−1·cm−2 in 70% H 2 /He feed gas at 900 °C. Humidification increases the hydrogen permeation flux and CO 2 or H 2 S reduces the hydrogen permeation flux. Hydrogen separation performance of La 1.95 Ca 0.05 Hf 2 O 7-δ material under external short circuit. [Display omitted] • Ca, Sr or Ba doping improves the sinter ability and conductivity of La 2 Hf 2 O 7. • All the samples display excellent chemical stability under the test conditions. • The Pt/La 1.95 Ca 0.05 Hf 2 O 7-δ /Pt membrane was utilized for hydrogen separation. • The membrane showed excellent resistance to CO 2 and H 2 S interference in utilization. [ABSTRACT FROM AUTHOR]

H2 production via membrane-assisted steam methane reforming (MA-SMR) can ensure higher energy efficiency and lower emissions compared to conventional reforming processes (SMR). Ceramic-supported Pd–Ag membranes have been extensively investigated for membrane-assisted steam methane reforming applications, with outstanding performance. However, costs, sealings for integration in the reactor structure, and resistance to solicitations remain challenging issues. In this work, the surface quality of a low-cost, porous Hastelloy-X filter is improved by asymmetric filling with α-Al2O3 of decreasing size and deposition of γ-Al2O3 as an interdiffusion barrier. On the modified support, a thin Pd–Ag layer was deposited via electroless plating (ELP), resulting in a membrane with H2/N2 selectivity >10,000. The permeation characteristics of the membrane were studied, followed by testing for membrane-assisted methane steam reforming. The results showed the ability of the membrane reactor to overcome thermodynamic conversion of the conventional process for all explored operating conditions, as well as ensuring 99.3% H2 purity in the permeate stream at 500 °C and 4 bar. [ABSTRACT FROM AUTHOR]

Graphene Oxide (GO) dispersed in a polymer blend of Polystyrene (PS)/Poly (methyl methacrylate) (PMMA) nanocomposite membranes have been prepared by the solution cast method for hydrogen gas permeation application. This paper reports a study of blends of PMMA and PS that were prepared in different ratios of weight percentage for PMMA: PS (80:20, 50:50 and 60:40) composite with 1 wt% of GO and 2 wt% of GO. The structural and morphological properties of these prepared composite membranes have been characterized using gas permeation, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). UV Spectroscopy and FT-IR have carried out the optical absorbance measurement of the composite membranes. The permeability measurements indicate that the GO nanofillers in blends of PS/PMMA have shown higher permeability for hydrogen gas than that of pure polymers. The gases used for the permeation measurements were H 2 , CO 2 , N 2 and CH 4. Selectivity has been calculated for H 2 /CO 2 , H 2 /N 2 and H 2 /CH 4 gas pairs and plotted to show Robeson's 2008 upper bound and compared with reported data. The transport properties of these gases have been compared with that of a neat membrane. The permeability of all gases has increased to that of the unmodified polymer membrane. The selectivity measurements show that GO composite with PS/PMMA blend membranes is highly selective for hydrogen gas from different gas pairs, therefore, these composite membranes can be used for hydrogen purification. There is a trade-off between permeability and selectivity parameters; GO nanofillers keep selectivity constant as permeability increases, which the nanogap theory could explain. [Display omitted] • GO nanofillers in blends of PS/PMMA have shown relatively higher permeability for hydrogen. • Selectivity for hydrogen in GO with PS/PMMA blend composite membranes is found to be higher. • Better separation performance of nanocomposite membrane is found in separation technology. • Porosimetry increases in different amount as GO content increases in polymers and in blends as well. [ABSTRACT FROM AUTHOR]

In the present study, bed poisoning characteristics of CO 2 as gaseous impurity in the La 0.9 Ce 0.1 Ni 5 based, "Metal Hydride Hydrogen Purification System (MHHPS)" and regeneration of poisoned bed are reported. The study was conducted by varying impurity content of CO 2 gas in the H 2 –CO 2 mixture, in the range of 10–50% by weight and the cyclic stability of alloy was tested with 10% CO 2 in H 2 –CO 2 mixture. The study was conducted on a lab scale reactor with 6 embedded cooling tube (ECT) filled with 1.2 kg of La 0.9 Ce 0.1 Ni 5. According to the experimental outcomes, the MHHPS was capable of delivery 99.99% pure hydrogen for CO 2 impurity up to 20%. However, for higher impurities level (20–50%), the purity level was in the range of 97.3–99.8%. With CO 2 as impurity, significant drop in the absorption capacity of the MHHPS was observed, which was in the range of 0.92 wt% to 0.67 wt% for impurity of 10–50%. However, the bed regeneration was performed, wherein the bed was desorbed and evacuated at 95 °C and 10−2 mbar, followed by absorption of pure hydrogen at 20 bar and 25 °C. Within 2-3 regeneration cycle, the alloy got regenerated and achieved storage capacity of 1.27 wt% in 200 s. • Working of La 0.9 Ce 0.1 Ni 5 based H 2 purification system is reported. • Presents results on poisoning characteristics of CO 2 on hydrogen purification system. • Purification capacity and cyclic stability for 10–50% CO 2 impurity is reported. • Bed regeneration characteristics of La 0.9 Ce 0.1 Ni 5 is reported. • Gas composition analysis using gas chromatography is reported. [ABSTRACT FROM AUTHOR]

1 H NMR (400 MHz, C 6 D 6): = 7.78 [t, 4 J H, F = 7.0 Hz, 3 H, Ar- H), 0.26 (s, 54 H, Si(C H 3) 3 ]. Keywords: triarylboranes; Lewis acids; frustrated Lewis pairs; hydrogenation; boron catalysis; hydrogen separation EN triarylboranes Lewis acids frustrated Lewis pairs hydrogenation boron catalysis hydrogen separation 2187 2192 6 10/31/23 20231127 NES 231127 Graph Triarylboranes are representative Lewis acids that are widely applied as catalysts, activators, sensors, and bioimaging agents. The formation of Et SB 3 sb P=O- B B I SP n sp i b was also confirmed by using SP 11 sp B NMR spectroscopy, and resonances that indicate the generation of four-coordinate boron species were observed at SB B sb = -0.4 ( B B SP 1 sp b ), -0.3 ( B B SP 2 sp b ), and -1.4 ( B B SP 3 sp b ). The NCIs between the individual I meta i -TMS groups probably play a critical role in enhancing the global and effective Lewis acidity of B B SP 1 sp b with respect to B B SP 2 sp b . [Extracted from the article]

Two‐dimensional (2D) metal–organic framework (MOF) membranes are considered potential gas separation membranes of the next generation due to their structural diversity and geometrical functionality. However, achieving a rational structure design for a 2D MOF membrane and understanding the impact of MOF nanosheet stacking modes on membrane separation performance remain challenging tasks. Here, we report a novel kind of 2D MOF membrane based on [Cu2Br(IN)2]n (IN=isonicotinato) nanosheets and propose that synergetic stacking modes of nanosheets have a significant influence on gas separation performance. The stacking of the 2D MOF nanosheets is controlled by solvent droplet dynamic behaviors at different temperatures of drop coating. Our 2D MOF nanosheet membranes exhibit high gas separation performances for H2/CH4 (selectivity >290 with H2 permeance >520 GPU) and H2/CO2 (selectivity >190 with H2 permeance >590 GPU) surpassing the Robeson upper bounds, paving a potential way for eco‐friendly H2 separation. [ABSTRACT FROM AUTHOR]

Hydrogen separation and purification are key to widespread application of hydrogen energy. Hydrogen permeable membranes based on lanthanum tungstate (LWO) attract attention due to favorable mechanical strength and chemical stability. However, industrial application of LWO‐based membranes has remained challenging because of modest hydrogen permeances. Here we report a novel graded porous supported symmetric (GPSS) LWO‐based membrane with improved transport properties, gas exchange dynamics, and operational stability, boosting stable hydrogen flux by several times over previously reported state‐of‐the‐art membranes. [ABSTRACT FROM AUTHOR]

Membrane separation technology provides an alternative to traditional thermally driven separations, owing to its advantages including low cost, energy-savings and environmental friendliness. However, the current membrane technology for gas separations using polymeric materials suffers the challenge of gas permeability-selectivity trade-offs. To overcome this hurdle, high-separation performance hybrid membranes are developed herein using microporous UiO-66-(OH)2 and PIM-1. Due to the stable interfacial hydrogen bonding, the MOF loading crosses the percolation threshold in hybrid membranes, and dual-path transport mechanisms govern the gas diffusion. Accordingly, the hybrid membranes with 40 wt% MOF loading exhibit a H2 permeability up to 9167.6 Barrer, transcending the 2008 H2/CH4 and H2/N2 Robeson upper bounds. Compared to neat PIM-1 membranes with a H2 permeability of 2378.3 Barrer, the H2 permeability of hybrid membranes increases over 285%, demonstrating ultra-high gas permeability. The design approach of hybrid membranes provides a viable pathway for the manufacture of hydrogen-bonded hybrid membranes with potential applications for hydrogen separation and CO2 capture.

This article focuses on the separation characteristics and research status of the metal palladium membrane and nickel membrane that are the most representative dense metal H2 separation membranes, the advantages and disadvantages of the two membranes in the high-temperature H2 separation process are compared and analyzed. The concept and research progress of the dense metal membrane reactors for synchronous hydrogen production and separation are also described, this article discusses the problems existing in the industrial application process of the dense metal membrane and prospects the optimization development direction in the future. [ABSTRACT FROM AUTHOR]

In this work, impedance spectroscopy has been employed to explore the electrochemical behaviour of a 15 cm2 complete tubular cell with BaZr 0.8 Ce 0.1 Y 0.1 O 3-δ (BZCY) electrolyte and two asymmetric Ni-BCZY cermet electrodes for hydrogen separation. Analyses of impedance spectra at different temperatures and gas compositions reveal that the thick inner electrode contributes most to the total polarisation resistance (R p). For R p there are four contributions with well-separated time constants of which gas phase hydrogen diffusion within the porous Ni-BZCY anode is predominant. The other three can be ascribed to proton migration through the space charge layer of the BZCY electrolyte adjacent to the Ni electrode, hydrogen redox charge transfer reactions, and hydrogen diffusion within Ni bulk. The present study guides the way to parameterise and, on this basis, optimise electrodes for scalable proton ceramic electrochemical cells. • Impedance spectroscopy on a complete proton ceramic tubular cell with asymmetric Ni-BCZY cermet electrodes. • Differentiates electrode contributions and identifies polarisation mechanisms. • Hydrogen gas diffusion limitation in the thick cermet dominates total polarisation under applied conditions. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to identify the environmental hotspots of lab-scale preparation of high purity porous Al2O3 pellets with suitable feature to work properly as metal layer-based deposition substrates for hydrogen separation membranes. The work intention was providing hints that may help the designing of upscaled systems, fundamental for the development of a possible future industrial production of hydrogen separation metal layer-based membranes technology. Methods: The goal of this study was achieved assessing and analyzing environmental impacts of Al2O3 pellet production at lab scale. Primary data were collected in Padua laboratories of National Research Council of Italy. Secondary data were retrieved from Ecoinvent 3.7 database. Life cycle assessment (LCA) was performed using Environmental Footprint 3.0 method employing SimaPro 9.3 as software. Moreover, the CML LCIA method v. 4.7 was used to verify the robustness analysis of characterized results. Results: Life cycle impact assessment highlighted as the main driver of environmental impacts was mainly associated to the pellet consolidation process and their morphological characterization stage. In particular, the impact of the first energy consuming process resulted strictly related to the peculiar energy mix used (linked to the laboratory geographical location). Conversely, morphological characterization stage was found to affect mainly the mineral resource depletion category due to the Au coating used for performing scanning electron microscope (SEM) analyses. Conclusions: The study identified the environmental hotspots related to lab-scale preparation of porous alumina pellets as substrate for hydrogen separation metal layer-based membranes. The optimization strategies evaluated in this work were addressed to improve the environmental profile of experimental activities considering several scenarios, in view of a possible industrial scale-up. [ABSTRACT FROM AUTHOR]

Because hydrogen is a high-quality, clean energy carrier, it is and will continue to be one of the key elements/fuels to help solve the climate problem. In addition, new chemical production processes and the development of high-efficiency fuel cells require high-purity hydrogen, as it is one of their critical components. The production of hydrogen from natural gas makes it possible to smoothly transition to "green energy". However, synthetically produced hydrogen contains other impurities and some unreacted substituents such as CO 2 , N 2 ,CH 4 , etc. We have reviewed the main technologies for hydrogen purification, such as pressure swing adsorption (PSA), and cryogenic distillation. The focus of the article will be on the description of hydrogen separation, including a membrane module and an electrochemical hydrogen compressor. The scalability of the technology and the high degree of purification make membrane technology a promising method for hydrogen purification and separation. Different properties of membranes, such as high resistance to poisoning in ceramic membranes or a high degree of purification in dense metal membranes, make it possible to create mixed technologies for hydrogen separation and purification. • PSA technology is a mature gas separation method for high-purity hydrogen. • Cryogenic methods are suited for separating hydrogen but not for high purity. • Membrane separation is most promising with dense palladium-based membranes. • Polymeric, ceramic, and carbon membranes are also used but with limitations. [ABSTRACT FROM AUTHOR]

Objective Hydrogen-blended natural gas pipeline is regarded as one of the important ways to transport hydrogen energy in large scale, low cost and long distance. In order to obtain high purity hydrogen, hydrogen-blended natural gas needs to be separated at the terminal. At present, the common hydrogen separation methods are not directly applicable to the separation of hydrogen-blended natural gas with low hydrogen concentration. Methods This paper introduces the principle, process parameters, advantages and disadvantages of the common hydrogen separation technology. Combined with the characteristics of hydrogen-blended natural gas, the coupling process route of "membrane separation + pressure swing adsorption" is determined, and the economic analysis is made on the separation process scheme of hydrogen-blended natural gas with hydrogen blending ratio of 10 mol%, 15 mol% and 20 mol%. The separation cost of each separation scheme is specified. Results The comprehensive separation cost of 10% hydrogen blending ratio is 0.846 7 yuan/m³ hydrogen, the comprehensive separation cost of 15% hydrogen blending ratio is 0.519 7 yuan/m³ hydrogen, and the comprehensive separation cost of 20% hydrogen blending ratio is 0.382 6 yuan/m³ hydrogen. Conclusions The separation cost of hydrogen-blended natural gas with low concentration is high, and its large-scale application still faces economic constraints and challenges. [ABSTRACT FROM AUTHOR]

With the extensive use of hydrogen energy, hydrogen separation membranes with proton–electron mixed conductors have broad application prospects in hydrogen separation and purification. Herein, La1.85M0.15Ce2O7−δ (M = Li, Na, K, Rb, and Cs; LMC) proton conductors are prepared. The electron paramagnetic resonance, Raman, and X‐ray photoelectron spectroscopy results indicate that the proposed method of replacing part of the La3+ in La2Ce2O7−δ with alkali metal ions produces more oxygen vacancies, which provides more possibilities for ion transport. Among them, La1.85Rb0.15Ce2O7−δ (LRC) exhibits the highest oxygen vacancy concentration. In addition, as the radius of the alkali metal doping ions increases, the corresponding LMC grains also increase. However, an excessively large ionic radius (Cs+) can hinder grain growth. LRC has the largest ionic radius, indicating that it has a smaller grain boundary resistance. This results in the maximum conductivity of the LRC (2.99 × 10−2 S cm−2) in the atmosphere of wet 20% H2 + 80% N2 at 900 °C. Similarly, in the hydrogen permeability test, the LRC exhibits the highest hydrogen flux (2.74 × 10−9 mol cm−2 s−1) at 900 °C. Moreover, an increase in temperature and hydrogen partial pressure on the feed side can promote hydrogen permeability. Therefore, it is a potential material for ceramic hydrogen separation membranes. [ABSTRACT FROM AUTHOR]

Metallic supports with sufficient surface quality to achieve highly selective thin Pd–Ag membranes require specific pre-treatments, are not readily available on the market and are generally very expensive. To reduce costs, rough and large media grade Hastelloy X filters have been acquired and pre-treated via polishing and chemical etching. The loss in gas permeance given by the polishing treatment proved fully recovered after chemical etching. A method to fill the large pores of the filters via aspiration of α-Al 2 O 3 water-powder suspension has been applied and characterized via imaging of the filled pores, inferential statistics, and capillary flow porometry measurements. The most suitable filler particle size for pore size distribution reduction has been identified as 18 μm, while a 5 μm filler proved optimal for further pore morphology improvement. The wide pore size distribution of the filters has thus been reduced up to 200 nm by filling with α-Al 2 O 3 particles of decreasing size, similarly to the ceramic supports used for thin Pd–Ag membranes deposition. A boehmite based interdiffusion barrier has been deposited, achieving further surface roughness reduction. A highly H 2 selective membrane has been obtained via simultaneous Pd–Ag plating on the pre-treated filter. [Display omitted] • A method to fill the pores of Hastelloy filters via aspiration of α-Al 2 O 3 water suspension has been developed. • The effect of α-Al 2 O 3 particle size on the surface quality has been studied with a statistical method. • The asymmetrical filling method can reduce the average pore size of the filters from 1.1 μm up to 200 nm. • A boehmite-based layer is used to change the surface quality and as interdiffusion barrier. • A highly H 2 -selective Pd–Ag membrane (∼40 000) has been obtained on the asymmetrically filled support. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to synthesize PdCu alloy membranes with firm, thin, and fcc phase structure (resistant to sulfur compounds), selectively permeable to hydrogen, using an electroless plating technique by creating an osmotic flux. First, coating studies were conducted without creating osmotic flux to determine the appropriate alloy formation temperature. Commercial porous borosilicate glass tubes were modified with alumina to form an interface that enhances the interaction between the coating and the support. The modified supports were cleaned and activated, then coated 3 times for 45 min in the Pd-based plating bath and then once for 15 min in the Cu-based plating bath. The coated supports were subjected to heat treatment at two different temperatures (550 and 650 °C) in a hydrogen environment for 8 h. Then, 650 °C, where the metals loaded on the surface were highly involved in the alloy structure and only the fcc phase was observed, was determined as the appropriate alloy temperature. Afterward, coating studies were conducted by creating osmotic flux with a 3 M sucrose solution, keeping the coating conditions and bath composition the same. From XRD analysis, fcc phase formation was observed in {111} {200} {220} planes in the membrane synthesized without osmotic flux, while alloy formation was detected in the {311} plane in addition to these planes in the membrane synthesized with osmotic flux. In this study, it has been shown that besides the temperature and time, the firmness of the metal layers formed before the heat treatment also affects the alloy formation in this plane. It was determined from SEM/EDS analyses that the membranes synthesized under the effect of osmotic flux were thinner, firmer, and homogeneous (⁓ 13.5 µm). Hydrogen transport parameters (T = 250 °C, ΔP = 101–304 kPa) were investigated in the synthesized membranes. In accordance with the literature, low hydrogen flux (0.04–0.09 mol/m2 s) and high selectivity values (αH2/N2:465–324) were determined in membranes synthesized with osmotic flux. Additionally, it was determined that this membrane remained stable in the hydrogen environment (T = 250 °C, ΔP = 203 kPa) for 96 h. The results of the study showed that conducting the electroless plating method with osmotic flux made positive contributions to the structure and hydrogen selectivity of the prepared alloy membranes. [ABSTRACT FROM AUTHOR]

Hydrogen is injected into the existing natural gas network to form hydrogen-rich compressed natural gas (HCNG), effectively addressing the high cost of hydrogen transmission. However, the traditional IES model cannot be used due to the hydrogen injection's effect on gas properties and the vague characteristics of the transport and separation processes. Therefore, this paper proposes an HCNG penetrated integrated energy system (HPIES) optimal dispatching method by comprehensively modelling the injection, transmission, and separation processes of HCNG. An HCNG mass flow rate model considering variable mixing ratio and unknown beginning flow direction is developed to describe the effect of hydrogen injection. Furthermore, the hydrogen separation model is established by introducing a combined membrane and pressure swing adsorption separation process. The tightening McCormick algorithm is proposed to solve quickly HPIES optimal dispatch problem with an acceptable feasibility check. Finally, case studies on the HPIES consisting of IEEE 39-bus power system and 20-node natural gas system validate the effectiveness of the algorithm and model. The results show that the average error is 0.031% for the bilinear term constraint. [Display omitted] • A model of HCNG penetrated integrated energy system (HPIES) is established. • The model considers the process of HCNG production, transport and separation. • An HCNG mass flow rate model is established to track the hydrogen mixing ratio. • Hydrogen separation is modeled based on membranes and pressure swing adsorption. • The HPIES optimal method based on tightening McCormick algorithm is proposed. [ABSTRACT FROM AUTHOR]

Membrane technology is an advanced hydrogen separation method that is of great significance in achieving hydrogen economy. Rare earth tungstate membranes have both high hydrogen permeability and remarkable mechanical/chemical stability, exhibiting good application prospects in hydrogen separation. This review provides the basic aspects and research progress on rare earth tungstate hydrogen separation membranes. The crystal structure, proton transport properties, and membrane stability under a chemical atmosphere are introduced. Different membrane construction designs, such as single-phase, dual-phase, and asymmetric rare earth tungstate membranes, are summarized. Lastly, the existing problems and development suggestions for tungstate membranes are discussed. [ABSTRACT FROM AUTHOR]

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.

This work analysed the permeation of binary and ternary H 2 -containing mixtures through a SAPO-34 membrane, aiming at investigating how hydrogen influences and its permeation is influenced by the presence of the other gaseous species, such as CO 2 and CH 4. We considered the behaviour of various gas mixtures in terms of permeability and selectivity at various temperatures (25–300 °C), feed pressures (400–1000 kPa) and compositions by means of an already validated mass transport model, which is based on surface and gas translation diffusion. We found that the presence of CO 2 and CH 4 in the H 2 -containing mixtures influences in a similar way the H 2 permeation, reducing its permeability of about 80% compared to the single-gas value because of their stronger adsorption. On the other hand, H 2 promotes the permeation of CO 2 and CH 4 , causing an increment of their permeability with respect to those as single gases. These combined effects reflected in interesting selectivity values in binary mixture (e.g., CO 2 /H 2 about 11 at 25 °C, H 2 /CH 4 about 9 at 180 °C), which showed the potential of SAPO-34 membranes in treating of H 2 -containing mixtures. [Display omitted] • Gas permeation of H 2 -containing mixtures through a SAPO-34 membrane. • Influence of temperature, feed pressure and composition on permeability and selectivity. • Hindering effect of the strongly adsorbed CO 2 and CH 4 on H 2 permeation. • Promoting effect of the faster H 2 on CO 2 and CH 4 permeation. [ABSTRACT FROM AUTHOR]