H2 Permeance Research Articles

Crystalline Metal–Organic Framework Coatings Engineered via Metal–Phenolic Network Interfaces

AbstractCrystalline metal–organic frameworks (MOFs) have garnered extensive attention owing to their highly ordered porous structure and physicochemical properties. However, their practical application often requires their integration with various substrates, which is challenging because of their weakly adhesive nature and the diversity of substrates that exhibit different properties. Herein, we report the use of amorphous metal–phenolic network coatings to facilitate the growth of crystalline MOF coatings on various particle and planar substrates. Crystalline MOFs with different metal ions and morphologies were successfully deposited on substrates (13 types) of varying sizes, shapes, and surface chemistries. Furthermore, the physicochemical properties of the coated crystalline MOFs (e.g., composition, thickness) could be tuned using different synthesis conditions. The engineered MOF‐coated membranes demonstrated excellent liquid and gas separation performance, exhibiting a high H2 permeance of 63200 GPU and a H2/CH4 selectivity of 10.19, likely attributable to the thin nature of the coating (~180 nm). Considering the vast array of MOFs available (>90,000) and the diversity of substrates, this work is expected to pave the way for creating a wide range of MOF composites and coatings with potential applications in diverse fields.

Hydrogen permselective membrane prepared by plasma treatment of porous ceramic substrates

Abstract Demand for hydrogen is increasing as we move toward a decarbonized society. Membrane separation methods have attracted attention as a way to reduce the cost of hydrogen production. In this study, we focused on boron nitride (BN) as a chemically stable porous substrate material. CVD treatment at 250°C has been investigated for porous BN, but selectivity did not develop. Therefore, we focused on atmospheric pressure plasma as a treatment method. The objective of this study is to develop a membrane with high hydrogen selective permeance by immersion in silicon alkoxide after plasma treatment. After plasma treatment for 100 s, the H2 permeance was 3.52×10−6 [mol m−2 s−1 Pa−1] and the H2/N2 permeance ratio was 18.25. Since molecular hydrogen can pass between the BN crystal faces, it is considered that silica reacted with the hydroxy groups formed on BN by plasma treatment and blocked the space between crystals. Therefore, it is suggested that the performance of the separation membrane changes depending on the number and distribution of hydroxyl groups by plasma treatment, and further stabilization is needed.

Development of high hydrogen permselective membranes by using a vapor treatment method

Abstract In recent years, the depletion of energy resources and global warming have led to the promotion of new energy resources. Hydrogen is attracting attention as one of the energy sources for the carbon-neutral society by 2050. Membrane separation is a method for separating and purifying hydrogen. In this study, we focused on developing high hydrogen permselectivity of silica membranes. We investigated the conditions necessary for membrane production to obtain a thin, dense separation layer. The results exhibited that the hydrogen permeation selectivity was enhanced in the silica membrane through the utilization of a 2-step deposition technique, which involves the combination of alternative feed and counter-diffusion chemical vapor deposition (CVD). The H2 permeance achieved by the 2-step method is 1.4×10−6 [mol m−2 s−1 Pa−1], representing 1.4 times higher than that of counter-diffusion CVD. In addition, the permeance ratio, which represents hydrogen selectivity, was significantly enhanced with the 2-step method, with H2/C3H8 = 260, twice as high as with CVD. Elemental mapping analysis of the cross-sectional structure revealed a concentration gradient in the deposited silica within the intermediate layer. This indicates that the silica separation layer may become an asymmetric structure. The 2-step method is expected to yield a thinner dense layer, which could contribute to improved permeance of silica separation membranes by reducing permeation resistance.

Development of a hydrogen permselective silica membrane and its application to the thermochemical water splitting method

Abstract The thermochemical water splitting IS process is one of the hydrogen production method to use a heat directly. The temperature of the thermal decomposition of water (4000 K) can be reduced under 700 K by introducing I2 and SO2 as recycling catalysts. One of the problems in the IS process is that the conversion of the HI decomposition reaction is low at about 20%. If a membrane reactor with the H2 permselective membrane is applied to the HI decomposition reaction, the hydrogen can be extracted to improve the HI conversion. We focus on a counter diffusion CVD method for the preparation method of the membranes. Two reactants (e.g. silica precursor and oxidant) are provided at the opposite side of the porous substrates and hybrid silica is deposited inside the pore of the substrate. The pore sizes are controlled by introducing organic functional groups to silica precursor. In this study, the silica hybrid membrane with high H2 permeation performance and high H2/HI selectivity were developed by introducing organic functional groups. Effects of the organic functional groups were summarized by using a pore model. The HI gas and other inorganic gases permeation performance were tested through silica hybrid membranes.

Synergistic interfacial interaction in polyetherimide/ZIF-7 mixed matrix membranes for enhanced H2/CO2 separation

Mixed matrix membranes (MMMs), consisting of a continuous polymer phase and a discontinuous molecular sieve phase, present a promising alternative to polymeric membranes for gas separations due to their advantages of high processability with outstanding separation efficiency. The suppression of sieve-in-a-cage and filler agglomerations, major challenges in existing MMMs, is systematically validated through a combination of polyimide and zeolitic imidazolate framework-7 (ZIF-7) nanofillers to enhance the H2/CO2 separation performance. The polyetherimide (Ultem) exhibits excellent interfacial interaction with ZIF-7 nanofillers within the MMMs, enabling the accommodation of high ZIF-7 concentrations, up to 40 wt%, due to its hydrophobic nature. The Ultem/ZIF-7 (60/40 wt/wt) MMMs represent significant enhancements in both H2 permeability and H2/CO2 selectivity, showing increases of 35 % and 65 %, respectively, compared to the pristine Ultem membrane. Furthermore, the enhancement in the intrinsic H2/CO2 separation performance of ZIF-7, estimated by the Maxwell equation, is likely attributed to the substantial rigidification of polymer chains in the vicinity of ZIF-7. Additionally, the difference in the activation energy of permeation for H2 and CO2 distinctly increases with ZIF-7 contents, highlighting the importance of the interfacial interaction in the separation performance of MMMs.

Thermally Annealed High-Aspect-Ratio ZIF-8 Nanoplates-Incorporated Mixed Matrix Membranes for Improved H2/CO2 Selectivity.

The main challenge in the preparation of MOF-based mixed matrix membranes is to construct a good interface morphology to improve the gas separation performance and stability of the membranes. Herein, high-aspect-ratio ZIF-8 nanoplates for H2/CO2 separation membranes were synthesized by direct template conversion. The ZIF-8 nanoplates were prepared with the commercial Matrimid polymer to form MMMs by the flat scraping method. The homogeneous dispersion of high-aspect-ratio nanoplates in the membrane and the good compatibility between the filler and the matrix caused by the thermal annealing operation improve the gas separation performance and mechanical properties of MMMs. The H2/CO2 selectivity of MMMs loaded with 30 wt % ZIF-8 nanoplates increased to 10.3, and the H2 permeability was 330.1 Barrer. This synthesis method can be extended to prepare various ZIF nanoplates with elevated aspect ratios to obtain excellent performance fillers for gas separation of MMMs. In addition, the thermal annealing operation allows more efficient gas separation in polymer membranes and is a feasible way to design excellent and stable MMMs.

Deep eutectic solvent engineered GO/ZrO2 nanofiller for mixed matrix membranes: An efficient hydrogen gas separation

AbstractThis study explores fabrication and characterization of mixed matrix membranes (MMMs) for gas separation, employing a cost‐effective solution casting method. Polycarbonate (PC) and polystyrene (PS) blends are combined with graphene oxide (GO) and zirconium dioxide (ZrO2) nanofillers, with and without a deep eutectic solvent (DES) obtained through hydrogen bond exchange. Various MMMs compositions (2–20 wt%) are systematically examined using diverse characterization techniques, including differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, porosity determination, and water contact angle analysis. The MMMs exhibit enhanced gas permeability and selectivity, surpassing conventional membrane materials. Notably, H2 gas permeability reaches outstanding levels, with the composition PC/PS‐DES‐GO/ZrO2 at 20 wt% (PBC20‐IV) demonstrating the highest value of 86.32 Barrer. This superior performance is attributed to the unique properties of ZrO2, increased sorption capacity of GO, and enhanced thermal stability due to DES. Permeability data for CO2, N2, O2, and CH4 also show significant values, aligning with the observed trends in H2 permeability. Robeson's plot for the H2/CO2 gas pair surpasses the 2008 upper bound, placing the MMMs in a novel category for gas separation membranes. The incorporation of DES‐modified nanofiller blend composites presents a promising strategy for the potential production of pure hydrogen.

Enhanced hydrogen selectivity of allylhydridopolycarbosilane (AHPCS)-derived silicon carbide membranes via air curing

Hydrogen is a critical element in numerous industrial processes and as a clean energy source. This study investigates Allylhydridopolycarbosilane (AHPCS)-derived membranes as a viable alternative to conventional Silica (Si) membranes for hydrogen separation. The AHPCS membranes were fabricated using a three-step process involving pre-firing at 300 °C in N2, air curing, and pyrolysis at 700 °C in N2. By optimizing the air-curing temperatures, the cross-linking of AHPCS-derived membranes was improved, leading to enhanced hydrogen selectivity. The highest H2 permeance of ∼1 × 10−6 mol/(m2 s Pa), accompanied by H2/N2 selectivity of ∼200 and H2/C3H8 selectivity of 3386, achieved through air curing at 600 °C followed by pyrolysis at 700 °C. AHPCS membranes showcased remarkable selectivity for H2/N2 with low H2 activation energy (3−5 kJ/mol), clearly surpassing silica membranes and demonstrating their superior performance. These findings underscore the potential of AHPCS membranes for gas separation and purification applications, marking a significant stride in membrane science.

Effect of cathode ink formulation on the hydrogen crossover and cell performance of proton exchange membrane water electrolyzers

The permeation of H2 through the membranes of proton exchange membrane water electrolyzers (PEMWEs) is a critical safety concern because of the risk of explosion when H2 mixes with O2 at the anode and increases in concentration. In this study, we investigated the modification of the cathode catalyst layer in the membrane electrode assembly as a strategy for achieving the safe operation of PEMWEs. The effects of the polytetrafluoroethylene (PTFE) content and type of ionomer in the cathode catalyst layer on the dissolved H2 concentration, H2 crossover, and electrochemical performance were investigated. The lowest dissolved H2 concentration and H2 permeation rate were achieved when 8 wt% PTFE was used. Consequently, the H2 volume fraction in O2 at the anode was less than 0.88 %. Additionally, using the Nafion ionomer (D520, ion exchange capacity: 1 mmol g−1), H2 volume fractions of 1.27 % and 1.34 % were obtained at 0.08 and 5 A cm−2, respectively. These values are below the lower explosion limit of H2 in O2 (4 %), implying that the PEMWE can be safely operated in the low-to-high current density range under ambient pressure. These results provide key guidelines for the design of high-safety cathode catalyst layers for PEMWEs.

Highly-efficient hydrogen purification with the T-C3N2 membrane via strain and charge engineering as well as their synergistic effect

The efficient separation and purification of high-purity hydrogen is imperative and desirable. We systematically explored the H2 purification performance of the T-C3N2 membrane with and without biaxial compressive (BC) strain and charge engineering by using MD simulations and DFT calculations. We found that the pure T-C3N2 membrane has relatively poor H2 selectivity as CO2 can also permeate through the membrane, and two modulation methods of BC-strain and charge were thus introduced separately to enhance the H2 separation performance for the first time. The T-C3N2 membrane with BC-strains modulation (1 %–3%) has excellent H2 permeance of 1.60 × 107–1.85 × 107 GPU at 300 K with 15.6 % enhancement with respect to the pure T-C3N2 membrane. The selectivity of H2 over gases (CO, N2, CO2, H2O, CH4) was drastically improved, for example, H2/CH4 is enhanced from 5.8 × 1020 to 2.1 × 1036 under 3 % strain engineering. The introduction of charge (1e–3e, 1e−–2e−) also enhances the H2 permeance of 1.47 × 107–1.68 × 107 GPU and the selectivity at 300 K. In particular, the charge (1e) and (1e−) modulations exhibit a desired permeance-selectivity trade-off for H2 purification with the enhancement of 5 % permeability and at least 1.3 times selectivity of H2 to other gases, respectively. Finally, the synergistic effect of BC-strain and charge on the H2 separation was studied, and it is much superior to separated BC-strain and charge engineering for H2 purification, where the H2 permeance enhances up to 1.86 × 107–1.89 × 107 GPU, and the H2 selectivity at 300 K is also enlarged at least ten times compared with that of the most effective modification of the isolated 2 % BC-strain and 1e charge, indicating synergistic effect further enhances the H2 separation performance. Therefore, the excellent modulations of appropriate BC-strain and charge engineering, particularly for their synergistic effect make the T-C3N2 membrane a promising candidate for highly permeant and selective H2 separation and purification that would be easily realized experimentally.

Supramolecular organic frameworks (SOFs) membrane with ultra-high hydrogen permeability for hydrogen purification: Microstructural design of JLU-SOF2

Simulating results showed that JLU-SOF2 has ultra-high hydrogen permeability (0.696 × 106 GPU) but low selectivity (7.46). Given the good structural designability of JLU-SOF2, it is valuable to develop the structure design of JLU-SOF2 for on-site hydrogen purification to improve selectivity and maintain high H2 permeability. In this study, the functional groups of JLU-SOF2 were modified to construct 13 membrane materials containing functional groups of different lengths. The effect of membrane materials modified with each functional group on hydrogen permeability and selectivity in mixed gases (CO2, CO, and H2) was investigated from a microscopic point of view utilizing molecular simulations. Results showed that all 13 functional groups could improve the gas selectivity, especially the -SO3H, -OCH3, and -CH2NH2 modified JLU-SOF2 membrane materials, which can 100 % intercept CO2 and CO and maintain an excellent H2 permeability (0.54 × 106GPU), which exceeded the industry standard by nearly 105 times. Molecular motion behavior analysis showed that stretching direction and length of functional groups are the key factors leading to different membrane pore sizes and play a crucial role in affecting gas transport.

Enhanced hydrogen separation performance of cobalt-doped microporous silica membranes: Influence of cobalt content and processing parameters

This research focused on synthesizing microporous silica and cobalt-doped silica through acid-catalyzed hydrolysis and condensation. The effects of various synthesis parameters (calcination temperature, cobalt content, and cobalt addition step) were investigated. The results confirmed that the presence of cobalt in the microporous structure enhances the performance of the silica membrane. However, the hydrothermal stability remained unchanged, which can be attributed to the pore size of the silica. The competitive cobalt-doped silica sol coated on a modified support, resulting in a membrane with better performance compared to the blank silica membrane. The membrane was subjected to single gas permeation tests: H2 permeance of 1.8 × 10−7 mol m−2 s−1 Pa−1 and H2/N2 selectivity of 58 at a low temperature of 200 °C. The high apparent activation energy (Ea) observed for H2, suggests the presence of a molecular sieving mechanism, which was further improved by incorporating cobalt into the microporous structure of silica.

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.

Technical evaluation of electrochemical separation of hydrogen from a natural gas/hydrogen mixture

In this work, we investigate the electrochemical separation of hydrogen from a 10% H2/methane natural gas blend using a single cell experimental setup for electrochemical hydrogen pumping (EHP). Results show that the overall efficiency for hydrogen separation is high, ranging from about 87% at 0.2 A/cm2 to 75% at 0.6 A/cm2. In addition, we develop a zero-dimensional model for the hydrogen separation process including the membrane permeation of H2 as well as CH4, N2, and CO2 as the main components in natural gas. We derive analytical expressions for the permeability of these gases as a function of temperature and membrane humidity using available permeability data. Although the presence of dilutive inert gases poses a challenge, the modelled data indicate that it should be possible to produce fuel cell quality hydrogen using a single hydrogen separation stage. Importantly, this indicates technological feasibility of distributing hydrogen for use in fuel cells through existing natural gas infrastructure. Extension of this research to combined hydrogen separation and compression within the same EHP unit is recommended as future work.

In-situ glass transition of ZIF-62 based mixed matrix membranes for enhancing H2 fast separation

Mixed matrix membranes (MMMs), combining the advantages of polymer membranes and porous materials, processing the potential to realize large-scale gas separation applications. However, the interfacial defects in MMMs greatly hindered gas separation performance improvement. Therefore, designing an MMM with high loading and good interfacial compatibility remains a critical issue in promoting the application of MMMs. Herein, during in-situ heating process, the melting of liquid ZIF-62 in PBI polymer can largely fill the interfacial defects in MMMs. The microporous transport channels of ZIF-62 glass in MMMs promoted the H2 diffusion and inhibited the CO2 and CH4 diffusion, thus enhancing the H2/CO2 and H2/CH4 separation of MMMs. For mixed gas testing, the 45 wt% ZIF-62 glass/PBI membrane had the maximum H2 permeability of 459 barrer, and its H2/CO2 and H2/CH4 selectivities were 23 and 57, higher than the gas separation upper bonds. In addition, ZIF-62 glass/PBI membrane exhibited stable separation performance under 1–5 bar pressure. Therefore, the rational combination of MOF glass and polymer matrix could provide promising potential for reducing the interfacial defects of high-loading MMMs, thus enhancing the gas separation performance.

Gravitational modulation of filler distribution in asymmetric mixed matrix membrane: Achieving high loading in skin layer

The fillers in asymmetric mixed matrix membranes (AMMMs) by phase inversion tend to distribute across the membrane, but less in the skin layer, resulting in limited enhancement of gas separation performance. In this work, an external gravity field is proposed to induce polystyrene-acrylate (PSA) modified hollow ZIF-8 nanospheres (PHZ) to settle and accumulate in the skin layer by the density difference between ZIF-8 and the polymer solution, then through phase inversion, the gravity induced AMMMs (GAMMMs) with improved ZIF-8 loading in skin layer is constructed. This is confirmed by the EDS analysis of the membrane cross-sections that more PHZ settle and accumulate in the skin layer, which enhances the filler loading by 330 % in comparison to the AMMMs without gravity sedimentation. Together with the hollow cavity of PHZ, the gas permeation can be improved greatly. Meanwhile, the PHZ can also guarantee the favorable interfacial compatibility by the hydrogen bonding interaction between the carboxyl groups in PSA with the PES polymer matrix, which is demonstrated by the slightly elevated Tg of GAMMMs over the ZIF-8/PES membrane. Consequently, the PHZ/PES GAMMMs can achieve high gas permeation while keeping sufficient selectivity at high filler loading in the skin layer. The PHZ-8d/PES GAMMM shows H2 permeance of 29.11 GPU and H2/CH4 of 83.04, which are 142.85 % and 5.99 % higher than those of ZIF-8/PES AMMM without gravity sedimentation, and exceeding the corresponding 2008 Robeson upper bound. This proposed GAMMM shows a great potential in the large-scale MMMs based gas separation.

Hydrogen purification in nitrogen-doped two-dimensional conjugated microporous polymers

Conjugated microporous polymers (CMPs) have emerged as advanced membranes with unique pore structures for the separation of small kinetic diameter gases, including H2. In this work, we present a comprehensive investigation into the potential of N-doped pyridinyl functionalized conjugated microporous polymers, denoted as CHNX (X = 1, 2, 6), in H2 purification by using molecular dynamic simulations. Our findings demonstrate that CHNX membranes exhibit exceptional H2 purification performance with both high H2 selectivity and permeance. Notably, the CHN6 membrane shows the highest H2 permeance of 2.61 × 10−5 mol m−2 s−1 Pa−1, owing to its larger pore area relative to the other membranes. Moreover, both CHN and CHN2 membranes achieve 100 % gas selectivity based on the molar sieving mechanism. To gain deeper insights into the gas separation process, we analyze the gas-membrane interaction, 2D density distribution, center of mass, mean square displacement, etc. The elucidation of these dynamics enhances our understanding of the underlying gas separation mechanisms. Ultimately, this work provides crucial theoretical guidance for the future development of gas separation membranes in hydrogen purification applications, thereby advancing the field of sustainable energy production.

Analysis of vacuum operation on hydrogen separation from H2/H2O mixture via Pd membrane using Taguchi method, response surface methodology, and multivariate adaptive regression splines

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.

High-Performance Anion Exchange Membrane Water Electrolyzers Enabled by Highly Gas Permeable and Dimensionally Stable Anion Exchange Ionomers.

Designing suitable anion exchange ionomers is critical to improving the performance and in situ durability of anion exchange membrane water electrolyzers (AEMWEs) as one of the promising devices for producing green hydrogen. Herein, highly gas-permeable and dimensionally stable anion exchange ionomers (QC6xBA and QC6xPA) are developed, in which bulky cyclohexyl (C6) groups are introduced into the polymer backbones. QC650BA-2.1 containing 50mol% C6 composition shows 16.6 times higher H2 permeability and 22.3 times higher O2 permeability than that of QC60BA-2.1 without C6 groups. Through-plane swelling of QC650BA-2.1 decreases to 12.5% from 31.1% (QC60BA-2.1)while OH- conductivity slightly decreases (64.9 and 56.2mScm-1 for QC60BA-2.1 and QC650BA-2.1, respectively, at 30 °C). The water electrolysis cell using the highly gas permeable QC650BA-2.1 ionomer and Ni0.8Co0.2O in the anode catalyst layer achieves two times higher performance (2.0Acm-2 at 1.69V, IR-included) than those of the previous cell using in-house ionomer (QPAF-4-2.0) (1.0Acm-2 at 1.69V, IR-included). During 1000h operation at 1.0Acm-2, the QC650BA-2.1 cell exhibits nearly constant cell voltage with a decay rate of 1.1µVh-1 after the initial increase of the cell voltage, proving the effectiveness of the highly gas permeable and dimensionally stable ionomer in AEMWEs.

Low-cost iron (Fe) hollow fiber membrane for hydrogen separation

Dense metal membranes are widely studied due to their promising performance in hydrogen separation. In this work, the low-cost dense iron (Fe) hollow fiber membranes (FeHFMs) were developed via the phase inversion and high-temperature sintering method. By tuning the preparation conditions, two typical gas-tight hollow fibers referred to as the sandwich- and honeycomb-structured membranes were successfully synthesized. H2 permeation behavior was well described by Sieverts equation based on the solution-diffusion mechanism. The sandwich-structured FeHFMs had an H2 flux of up to 7.51 mmol m−2 s−1 when operated at a temperature of 850 °C. In comparison, the honeycomb-structured FeHFMs further enhanced the H2 flux by a factor of 3.2 due to the optimized membrane morphology with only one single dense iron layer. The developed FeHFMs showed superior H2 permeation stability in thermal shock tests (40 h) and long-term stability tests (120 h). This work also expanded the potential application horizons of the FeHFMs, which can be easily tailored into porous or dense structures by tuning the sintering conditions.