Pd Composite Membranes Research Articles

Hydrogen production by steam methane reforming in membrane reactor equipped with Pd membrane deposited on NiO/YSZ/NiO multilayer-treated porous stainless steel

In this study, we prepared a Pd composite membrane with high hydrogen permeance and thermal stability on a tubular porous stainless steel (PSS) support by ethylene diamine tetraacetic acid-free electroless plating. The conventional yttria-stabilized zirconia (YSZ) was replaced with a NiO/YSZ/NiO multilayer as the diffusion barrier, and the latter was introduced on a PSS tube (diameter of 12.7 mm, length of 450 mm, and surface area of 175 cm2). A long-term thermal stability test revealed that the NiO/YSZ/NiO multilayer significantly reduced the growth rate of nitrogen leakage. The test was carried out for ~1150 h on a 2.5-µm thick Pd membrane deposited on a NiO/YSZ/NiO/PSS tube (diameter of 25.4 mm, length of 450 mm, and surface area of 350 cm2). The hydrogen permeance obtained at the end of the test was 3.81 × 10−3 mol m−2 s−1 Pa−0.5, and the H2/N2 selectivity was ~87 at a temperature of 773 K and pressure difference of 101.3 kPa. The rate of increase in nitrogen leakage during the test was 3.05 × 10–11 mol m−2 s−1 Pa−0.5 h−1, which demonstrated the ability of the NiO/YSZ/NiO multilayer to mitigate nitrogen leakage. To produce hydrogen using the Pd composite membrane reactor, steam methane reforming was conducted under the following operating conditions: pressure, 430–1114 kPa; temperature, 883 K; and gas hourly space velocity, 1000 h−1. The reaction yielded a methane conversion and hydrogen recovery of 75.1% and 97.9%, respectively. The permeate stream was composed of 93.1 vol% H2, 0.6 vol% CO, 1.8 vol% CH4, and 4.5 vol% CO2. The gas composition of the permeate stream was suitable for use as fuel in a high-temperature polymer electrolyte membrane fuel cell.

Support mass transfer resistance of Pd/ceramic composite membranes in the presence of sweep gas

The present paper aims at reducing the general lack of fundamental understanding about the effects of sweep gas on membranes supported on porous substrates. This is necessary to design better performing membranes for hydrogen purification and CO2 capture applications. Sweep gas is a widely considered option for enhancing the separation performance of hydrogen-selective Pd membranes in e.g. pre-combustion carbon capture and H2 production via low-temperature steam reforming. However, additional mass transfer resistance arises when using sweep gas with composite membranes due to its diffusion into the porous support. In order to assess this issue quantitatively, the influence of N2 sweep gas was systematically studied over a wide permeate pressure range using a 5µm thick Pd membrane supported on an asymmetric ceramic support tube. Experiments were carried out between 300 and 500°C at a trans-membrane pressure difference of 100kPa. These measurements were complemented with mathematical modelling to elucidate the mass transfer resistance associated with the sweep gas. In general, the mass transfer resistance of the support grew substantially with permeate pressure and increasing sweep rate, contributing up to 40% to the total mass transfer resistance at the highest investigated permeate pressure (1MPa). The negative impact of higher permeate pressures on the permeating fluxes could be effectively compensated by using relatively small sweep flow rates up to 100mLmin−1. Further increase of the sweep gas amount improved the permeation flux only by moderate margins albeit the sweep gas effect was a little stronger at higher permeate pressures. For example, the H2 permeation rate improved by ca. 29% (38%) when raising the sweep flow rate from 100mLmin−1 to 500mLmin−1 at 400°C and 100kPa (900kPa) permeate pressure. The relative permeation rate improvement with sweep rate became weaker with increasing temperature. The reduction of the support mass transfer resistance appears to be a promising strategy for enhancing hydrogen permeation through Pd composite membranes in situations that require the application of sweep gas.

Hydrogen production by steam methane reforming in a membrane reactor equipped with a Pd composite membrane deposited on a porous stainless steel

With the aim of producing hydrogen at low cost and with a high conversion efficiency, steam methane reforming (SMR) was carried out under moderate operating conditions in a Pd-based composite membrane reactor packed with a commercial Ru/Al2O3 catalyst. A Pd-based composite membrane with a thickness of 4–5 μm was prepared on a tubular stainless steel support (diameter of 12.7 mm, length of 450 mm) using electroless plating (ELP). The Pd-based composite membrane had a hydrogen permeance of 2.4 × 10−3 mol m−1 s−1 Pa−0.5 and an H2/N2 selectivity of 618 at a temperature of 823 K and a pressure difference of 10.1 kPa. The SMR test was conducted at 823 K with a steam-to-carbon ratio of 3.0 and gas hourly space velocity of 1000 h−1; increasing the pressure difference resulted in enhanced methane conversion, which reached 82% at a pressure difference of 912 kPa. To propose a guideline for membrane design, a process simulation was conducted for conversion enhancement as a function of pressure difference using Aspen HYSYS®. A stability test for SMR was conducted for ∼120 h; the methane conversion, hydrogen production rate, and gas composition were monitored. During the SMR test, the carbon monoxide concentration in the total reformed stream was <1%, indicating that a series of water gas shift reactors was not needed in our membrane reactor system.

Methane steam reforming using a membrane reactor equipped with a Pd-based composite membrane for effective hydrogen production

Herein, a methane steam reforming (MSR) reaction was carried out using a Pd composite membrane reactor packed with a commercial Ru/Al2O3 catalyst under mild operating conditions, to produce hydrogen with CO2 capture. The Pd composite membrane was fabricated on a tubular stainless steel support by the electroless plating (ELP) method. The membrane exhibited a hydrogen permeance of 2.26 × 10−3 mol m2 s−1 Pa−0.5, H2/N2 selectivity of 145 at 773 K, and pressure difference of 20.3 kPa. The MSR reaction, which was carried out at steam to carbon ratio (S/C) = 3.0, gas hourly space velocity (GHSV) = 1700 h−1, and 773 K, showed that methane conversion increased with the pressure difference and reached 79.5% at ΔP = 506 kPa. This value was ∼1.9 time higher than the equilibrium value at 773 K and 101 kPa. Comparing with the previous studies which introduced sweeping gas for low hydrogen partial pressure in the permeate stream, very high pressure difference (2500–2900 kPa) for increase of hydrogen recovery and very low GHSV (<150) for increase hydraulic retention time (HRT), our result was worthy of notice. The gas composition monitored during the long-term stability test showed that the permeate side was composed of 97.8 vol% H2, and the retentate side contained 67.8 vol% CO2 with 22.2 vol% CH4. When energy was recovered by CH4 combustion in the retentate streams, pre-combustion carbon capture was accomplished using the Pd-based composite membrane reactor.

Controllable growth of defect-free zeolite protective layer on the surface of Pd membrane for chemical stability enhancement

Pd membranes play a critical role in hydrogen purification due to excellent hydrogen permeability and selectivity. However, the poor chemical stability of Pd membranes when exposed to inclusion gases or organic reactants severely restricts their commercial applications. Herein, a novel strategy is developed to synthesize a thin and compact zeolite layer on the surface of Pd membrane which acts as an “armor” to protect it from being damaged by poisoning species. The results show that the zeolite membrane was NaA type and defect-free when using Si/Al ratio of 7.5 and silica sol as Si source after two-step hydrothermal synthesis. The variations of H2 permeance is monitored when Pd and zeolite-Pd composite membranes are exposed to 40% (ethanol/H2O) or 0.2% tetrahydrofuran (THF)/10% N2 in hydrogen atmosphere. Reactions between ethanol and water on Pd active sites are undetected, indicating the reactants are completely out of contact with Pd membrane in the presence of zeolite protective layer. Especially, compared to pure Pd membrane, almost 80% H2 permeance decline is constrained by the zeolite “armor” at 350 °C and W/E = 6. Moreover, the zeolite protective layer obviously enhances the chemical stability of Pd membrane by suppressing THF cracking and Pd active sites coverage.

Surface activation inspires high performance of ultra-thin Pd membrane for hydrogen separation

Pd-based membranes play a critical role in the field of hydrogen purification and small-scale hydrogen generation. The microstructure and composition of ultra-thin Pd membranes immediately determines their performance and stability, which are however complex and elusive. We applied for the first time a novel technique of environmental scanning electron microscopy (ESEM) together with EDS analysis for in-situ investigation of microstructure and composition of Pd composite membranes under gas-thermal treatment. It enables step by step analysis of the evolution process and offers more meticulous details compared to ex-situ technologies through analysis at exactly the same location of membrane samples. Here we observed the elimination of Pd crystallites as well as the homogenization/diffusion along the whole membrane surface following high T treatment under inert gas or H2 atmosphere. Gradual evolution of microhillocks on Pd membrane surface was resulted due to α−β phase transition or exposure to either O2 or H2O, which can be effectively “smoothened” out during H2 treatment. The exposure to steam exhibited a mild oxidation effect without pinhole formations, which appears a more appropriate surface cleaning process compared to air/oxygen treatment. A significant interlayer diffusion was revealed between Pd layer and ZrO2/alumina substrate in H2/O2/H2O atmosphere.

Defect size analysis approach combined with silicate gel/ceramic particles for defect repair of Pd composite membranes

Pd composite membranes show great potential in several important fields, such as high-purity H2 separation and production, due to unique permeability to hydrogen and its isotopes. However, the significant defect formation on palladium membranes and following decline in H2 selectivity resulted from either preparation process or thermal/chemical stability issues exist as a great challenge for their commercial applications. The currently existing techniques for defect repair of Pd composite membranes show either high complexity or limited effect thus limiting their practical applications. In this study, we presented a novel approach, i.e., strongly adhesive and high temperature resistant silicate gel (HTRSG)/ceramic particles, in combination with home-developed “modified” liquid–liquid displacement porometry (MLLDP) for defect size distribution analysis, where the latter can provide important guidance for the selection of appropriate particles sizes. The experimental results with thin Pd membranes indicated significant improvement in H2 permselectivity without decreasing H2 permeance after defect repair treatment. Moreover, silicate gel exhibits great durability under high temperature conditions. This approach features high simplicity, effectiveness and low cost, and is especially suitable for on-site repair of spent membranes in future applications. In addition, it is universal for defect repair of other inorganic membranes, and can also be used for the sealing of membrane modules.

Hydrogen permeation in composite Pd-membranes prepared by conventional electroless plating and electroless pore-plating alternatives over ceramic and metallic supports

Composite palladium membranes are attracting great attention for hydrogen separation and membrane reactor applications, due to the complete hydrogen selectivity with reasonably high permeability and suitable mechanical stability. These membranes are usually prepared by depositing a thin Pd layer over ceramic or metallic supports, which give to the system the necessary mechanical resistance. The Pd incorporation is generally made by electroless plating (ELP), although there is still no fully optimized and universally accepted method, and many researches are currently devoted to the generation of thin and homogeneous metallic coatings with good adhesion and resistance to real conditions. Among the many studies, very few compares directly the properties of the two different supports (metallic or ceramic) on the overall membrane structure and performance. In the present work, the permeation behavior of several Pd-composite membranes, prepared by conventional ELP and by a novel pore-plating method (ELP-PP) has been studied on both ceramic and metallic supports. The membrane prepared over a tubular ceramic support by conventional ELP shows a permeability in the range of 2.5–3.6·10−6 mol s−1 bar−0.5 m, with nearly complete ideal selectivity and Pd thickness around 14 μm. With the alternative preparation method, ELP-PP, despite the lower Pd thickness, 8 μm, and also complete selectivity, lower hydrogen fluxes were observed with a permeability ranging from 5.8 to 8.5·10−7 mol s−1 bar−0.5 m. This behavior can be explained by considering that the pore-plating method leads to a Pd deposition over the external surface of the support but also inside the pores, generating an effective Pd thickness higher than that obtained with the conventional ELP. In this manner, the real behavior of the membrane is equivalent to a conventional 33 μm thick palladium layer. Finally, these results are compared replacing the ceramic support by a metallic one (PSS), which led to an increase in the minimum thickness necessary to achieve a totally dense membrane (Pd thickness, 9 μm), and, consequently, to a reduction of the observed transmembrane flux. However, in this case a lower deposition of palladium inside the pores of the support is observed thus causing a lower resistance to the hydrogen permeation with respect to ceramic supported membranes.

Performance of Pd composite membrane prepared by organic–inorganic method in WGS membrane reactor

ABSTRACTH2 production via water–gas shift (WGS) reaction in a Pd membrane reactor prepared by the electroless plating technique (ELP) “organic–inorganic” method was investigated. Pd nanoparticles embedded polyethylene glycol (PEG) was used as a polymer template during the activation step. Gas permeation results showed an infinite selectivity for H2/N2 with a H2 flux of 0.004–0.016 mol/m2·s depending on operating conditions while it decreased until 0.0005 mol/m2·s for gas mixtures. Furthermore, WGS membrane reactor experiments showed a maximum CO conversion of 98.5% with a H2 recovery of 16% at 450°C. The membrane performance was consistent during WGS catalytic membrane reactors (CMR) tests, thereby confirming the stability of the obtained membrane.

Palladium clusters deposited on the heterogeneous substrates

To improve the performance of the Pd composite membrane prepared by the cold spraying technology, it is extremely essential to give insights into the deposition process of the cluster and the heterogeneous deposition of the big Pd cluster at the different incident velocities on the atomic level. The deposition behavior, morphologies, energetic and interfacial configuration were examined by the molecular dynamic simulation and characterized by the cluster flattening ratio, the substrate maximum local temperature, the atom-embedded layer number and the surface-alloy formation. According to the morphology evolution, three deposition stages and the corresponding structural and energy evolution were clearly identified. The cluster deformation and penetrating depth increased with the enhancement of the incident velocity, but the increase degree also depended on the substrate hardness. The interfacial interaction between the cluster and the substrate can be improved by the higher substrate local temperature. Furthermore, it is found that the surface alloys were formed by exchanging sites between the cluster and substrate atoms, and the cluster atoms rearranged following as the substrate lattice arrangement from bottom to up in the deposition course. The ability and scope of the structural reconstruction are largely determined by both the size and incident energy of the impacted cluster.

“Defect-free” interlayer with a smooth surface and controlled pore-mouth size for thin and thermally stable Pd composite membranes

Thin and thermally stable Pd membrane can be successfully coated on “defect-free” alumina sol/γ-Al2O3 interlayer with a controlled pore-mouth size of ca. 0.08 μm obtained by modified sol–gel method on macroporous α-Al2O3 support. The “modified” bubble-point method and home-developed “modified” liquid-liquid displacement method were used to check the size and amount of defects (>3 μm), and characterize pore-mouth size distribution of interlayers, respectively. The modified sol–gel method shows superiority in smoothening out defects and bumps compared to conventional suspended particles sintering method as the incorporation of alumina sol–gel particles can significantly improve the adhesion and dispersal uniformity of γ-Al2O3 particles. The synthesized Pd composite membranes of 4.5 μm thickness exhibit high hydrogen permeance and selectivity compared to similar studies. In addition, the good membrane stability was verified by the long-term operation under hydrogen permeation conditions. This can be mainly ascribed to the formation of defect-free and smooth interlayer which effectively suppress the shear stress between Pd layer and intermediate layer when enduring thermal cycles and hydrogen adsorption and desorption cycles.

Thermal stability study of Pd-composite membrane fabricated by surfactant induced electroless plating (SIEP)

ABSTRACTOver the years, several different methods have been developed by modifying the conventional electroless plating (CEP) technique to fabricate dense thin Pd composite membranes with high H2 permselectivity. In this study, Pd composite membranes on macroporous stainless steel substrate (MPSS) were fabricated using CEP and novel surfactant induced electroless plating (SIEP) methods. The structural characteristics of CEP and SIEP fabricated Pd membranes were investigated before and after the heat treatment using SEM, XRD, EDS, and AFM techniques. The H2 permselectivity performance of the SIEP membranes was compared with that of CEP at different temperatures and trans-membrane pressures in the range of 523-823 K and 20-100 psi, respectively. The long-term thermal stability test of SIEP fabricated membranes was carried out on two different membranes, fabricated on MPSS substrates with and without oxide layer at 15 psi trans-membrane pressure and thermal cycling of 573-723-573 K. The microstructure analysis revealed that SIEP membranes have finer grains and diffused grain boundaries resulting in uniform, smooth, continuous, and pinhole free Pd-film. The SIEP membrane showed eight-fold higher H2 flux (1.7172 mol/m2/s) and four-fold higher H2 selectivity (~148) at 823 K and 100 psi trans-membrane pressure, compared to CEP membrane. Pd/MPSS membrane subjected to test for long-term performance and thermal cycling showed stable performance up to 1200 h while maintaining infinite H2 selectivity. Interestingly, although the thickness of Pd/oxi-MPSS (13.49 µm) membrane was higher than that of Pd/MPSS (11.6 µm) membrane, the H2 flux of Pd/oxi-MPSS membrane was two times higher than that of Pd/MPSS, attributed to the effective action of oxide layer as diffusion barrier.

The oncoming energy vector: Hydrogen produced in Pd-composite membrane reactor via bioethanol reforming over Ni/CeO2 catalyst

A model bioethanol steam reforming reaction is performed in a thin composite Pd membrane reactor by using Ni/CeO2 catalyst. A 7.5wt.% Ni/CeO2 catalyst was prepared by Solution Combustion Synthesis using urea as fuel. The obtained powder was characterized by X-ray diffraction (XRD), N2-physisorption, CO-chemisorption and temperature programmed reduction (TPR). A 8μm thin Pd-layer deposited onto a porous Al2O3 support constitutes the membrane allocated in the membrane reactor module, where the catalyst is packed in the annulus. The H2 perm-selectivity of the composite membrane (expressed as H2/N2 ideal selectivity) is around 4700 at 400°C, Δp=0.5bar and in fresh membrane conditions.The bioethanol reforming is carried out at 400°C and the reaction pressure ranges from 2.0 to 3.0bar as well as GHSV from 5000 to 15,000h−1. The best performance of the membrane reactor is achieved at 400°C, 3.0bar and GHSV=5000h−1 where the ethanol conversion is around 98%, with more than 65% of hydrogen recovered in the permeate side. Furthermore, the influence of the byproducts present as impurities in the model bioethanol mixture on the membrane reactor performance is also evaluated.

The influence of heat treatment on the thermal stability of Pd composite membranes

In this work, the influence of high temperature heat treatments (>640°C) on the thermal stability of Pd composite membranes was investigated. Several Pd composite membranes (<7µm thick) were deposited by the electroless plating method onto the outer diameter of two different types of tubular porous supports. These membranes were subjected to different high temperature annealing processes and the thermal stability and microstructural evolution were studied. It was found that employing such heat treatments improved the thermal stability of the membranes when operated at lower temperatures; evidenced by a suppression of the rate at which hydrogen selectivity toward nitrogen declined over time at a given temperature. Heat pretreatment was also found to produce similar desirable effects under synthetic water gas shift mixtures containing up to 5mol% CO. SEM images of the microstructural evolution as a function of temperature revealed that porosity that is typically present in as-deposited electroless plated films is significantly reduced after heat treatment.

CuO/ZnO catalysts for methanol steam reforming: The role of the support polarity ratio and surface area

The effect of surface area and polarity ratio of ZnO support on the catalytic properties of CuO/ZnO catalyst for methanol steam reforming (MSR) are studied. The surface area of ZnO was varied changing the calcination temperature, and its polarity ratio was modified using different Zn precursors, zinc acetate and zinc nitrate. It was found that the copper dispersion and copper surface area increase with the surface area of the ZnO support, and the polarity ratio of ZnO strongly influences the reducibility of copper species. A higher polarity ratio promotes the reducibility, which is attributed to a strong interaction between copper and the more polar ZnO support. Interestingly, it was observed that the selectivity of CuO/ZnO catalysts (lower CO yield) increases with the polarity ratio of ZnO carriers. As another key result, CuO/ZnOAc375 catalyst has proven to be more selective (up to 90%) than a reference CuO/ZnO/Al2O3 sample (G66-MR, Süd Chemie).The activity of the best performing catalyst, CuO/ZnOAc-375, was assessed in a Pd-composite membrane reactor and in a conventional packed-bed reactor. A hydrogen recovery of ca. 75% and a hydrogen permeate purity of more than 90% was obtained. The Pd-based membrane reactor allowed to improve the methanol conversion, by partially suppressing the methanol steam reforming backward reaction, besides upgrading the reformate hydrogen purity for use in HT-PEMFC.

A highly permeable hollow fibre substrate for Pd/Al2O3 composite membranes in hydrogen permeation

In this study, a highly permeable ceramic hollow fibre substrate has been fabricated for developing Pd composite membranes. The substrate consists of one thin outer sponge-like layer for depositing Pd membranes by electroless plating and a plurality of self-organized micro-channels for reducing gas permeation resistance. A dense defect-free Pd membrane with approximately 1 μm was formed on the outer surface of the sponge-like layer, which suggests a great uniformity of the substrate. As a result, a hydrogen permeation flux of 0.87 mol s−1 m−2 can be achieved at 450 °C and 165 KPa. Hydrogen permeation of the several composite membranes with different Pd thicknesses (1.0 and 3.3 μm) and different substrates sintered at different temperatures (1300 and 1400 °C) was also investigated. It was found that an intermediate layer, which is normally formed due to the Pd penetration during the electroless plating, shows an adverse effect in hydrogen permeation, especially when the Pd membrane is very thin.

Hydrogen production in a Pore-Plated Pd-membrane reactor: Experimental analysis and model validation for the Water Gas Shift reaction

A laboratory reactor equipped with a Pd-composite membrane prepared by ELP “pore-plating” method (Pd thickness of 10.2 μm) has been used for performing the water gas shift reaction (WGSR). Reaction experiments were carried out with and without the membrane at different operating conditions: H2O/CO ratio (1–3), temperature (350–400 °C) and GHSV (4000–5500 h−1). In all cases, CO conversion was found to be higher when using the membrane to separate hydrogen. The membrane maintained the integrity with complete selectivity to H2. The membrane reactor has been modelled using a 2D mathematical model, capable of modelling the non-ideal flow pattern formed in this type of reactors. The model predicts the experimental CO conversion with an accuracy of ±10%. The proposed model was used as a tool in the scale-up of a membrane reactor for the water–gas-shift reaction (feed: 100 m3/h synthesis gas), designed to achieve high CO conversion (>99%) and hydrogen recovery (>99.5%). The permeation of hydrogen through the membrane was found to be ruled by mass transfer in the membrane support and palladium layer.

Synthesis of a zeolite membrane as a protective layer on a metallic Pd composite membrane for hydrogen purification

A zeolite membrane was synthesized on the surface of Pd membrane by seed-free hydrothermal synthesis. The zeolite membrane, which was used as an “armor”, offered good protection to the Pd membranes, significantly suppressing hydrogen permeance loss.

Evaluation of Pd composite membrane for pre-combustion CO2 capture

Carbon capture with hydrogen-selective Pd membranes can be realized as highly integrated process and CO2 can be separated at high pressure without employing environmentally harmful sorption agents. This study investigates the technical viability of using ultrathin Pd/ceramic composite membranes with innovative ceramic-to-metal connections under conditions that are practically interesting for natural gas-fired power stations, i.e. high feed and permeate pressures and high H2 recovery at elevated temperature. The 90% CO2 capture target was well exceeded during a 150 day test in water gas-shifted reformate at 673K. After system stabilization 98% carbon were held back by the membrane while 98% H2 were separated at nominally 99.5% H2 purity. Special attention has been paid to long-term operation effects on the 2–4μm thick Pd layer. These include the development of a striking, cavernous Pd morphology which increases mechanical stability of the composite membrane, a somewhat reduced but steady H2 permeability, and the disappearance of most membrane defects. The latter is attributed to carbon deposits as exit flow analyses point to CO2 reduction preserving effectively membrane selectivity. Altogether, carbon capture with supported Pd membranes projects as feasible from a technological vantage point.

Pd and Pd–Ni alloy composite membranes fabricated by electroless plating method on capillary α-Al2O3 substrates

Novel home-made porous capillary α-Al2O3 substrates were used as mechanical supports for the Pd-based composite membranes for hydrogen permeation. The rough surface of the substrates with large open pores were modified by vacuum sol–gel dip-coating followed by high temperature calcination treatment. After the introduction of the electroless plating catalysts of Pd particles on the modified surface by an improved catalyzing process, the defect-free Pd and Pd–Ni alloy thin membranes were deposited by cost-effective and facile electroless plating technique. The Pd composite membranes showed a hydrogen permeance of 2.55 × 10−3 mol/(s m2 Pa0.5) at 500 °C, and 730 for the permselectivity of H2/N2. The Pd–Ni alloy composite membranes showed a hydrogen permeance of 2.74 × 10−3 mol/(s m2 Pa0.5), and 640 for the permselectivity of H2/N2 at the same temperature. The Pd and Pd–Ni membranes showed good long-term permeation stability at 500 °C under hydrogen permeation condition. Moreover, the Pd–Ni alloy composite membrane showed a better hydrogen permeation stability of more than 100 h at 300 °C under hydrogen permeation condition without obvious hydrogen embrittlement occurred.