Improved hydrogen permeation through thin Pd/Al2O3 composite membranes with graphene oxide as intermediate layer

Here we proposed the decreasing in the roughness of asymmetric alumina (Al₂O₃) hollow fibers by the deposition of a thin graphene oxide (GO) layer. GO coated substrates were then used for palladium (Pd) depositions and the composite membranes were evaluated for hydrogen permeation and hydrogen/nitrogen selectivity. Dip coating of alumina substrates for 45, 75 and 120 s under vacuum reduced the surface mean roughness from 112.6 to 94.0, 87.1 and 62.9 nm, respectively. However, the thicker GO layer (deposited for 120 s) caused membrane peel off from the substrate after Pd deposition. A single Pd layer was properly deposited on the GO coated substrates for 45 s with superior hydrogen permeance of 24 × 10⁻⁷ mol s⁻¹m⁻² Pa⁻¹ at 450 °C and infinite hydrogen/nitrogen selectivity. Activation energy for hydrogen permeation through the Al₂O₃/GO/Pd composite membrane was of 43 kJ mol⁻¹, evidencing predominance of surface rate-limiting mechanisms in hydrogen transport through the submicron-thick Pd membrane.     

Preparation of palladium membrane on Pd/silicalite-1 zeolite particles modified macroporous alumina substrate for hydrogen separation

A palladium composite membrane was successfully fabricated by electroless plating on a macroporous alumina tube. Pd/silicalite-1 zeolite particles were employed to reduce the pore size of the alumina support and improve its surface roughness. Moreover, the Pd⁰ existed in the Sil-1 particle can avoid the time consuming sensitization and activation steps for palladium seeding. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction (XRD) analysis were conducted for analyzing the detailed microstructure of the palladium composite membrane. The hydrogen permeation performance of the resulting palladium membrane was investigated at temperatures of 623 K, 673 K, 723 K and 773 K. The hydrogen permeance of 1.95 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with an H₂/N₂ ideal selectivity of 1165 for the palladium membrane was obtained at 773 K. Furthermore, the resulting palladium membrane was stable for a long-term operation of 15 days at 673 K.     

Hydrogen separation by thin vanadium-based multi-layered membranes

Thanks to their high hydrogen permeability, vanadium based alloys can be a valuable and sustainable alternative to palladium alloys, commonly employed in commercial membranes for hydrogen purification/separation. In this work, the unprecedented deposition of micrometric vanadium-based multilayers and their investigation as hydrogen selective membranes have been reported. In particular, this work describes the use of High Power Impulse Magnetron Sputtering, a technique easily scalable also for complex geometries, for the deposition of dense and crystalline Pd/V₉₃Pd₇/Pd multilayers with total thickness <7 μm onto porous alumina. These membranes showed high hydrogen fluxes in the 300–400 °C range, up to 0.26 mol m^?2 s^?1 at 300 kPa pressure difference and 375 °C, as well as an unexpected and significant resistance to hydrogen embrittlement and to syngas in operating conditions.     

Palladium composite membrane fabricated on rough porous alumina tube without intermediate layer for hydrogen separation

A thin palladium composite membrane without any modified layer was successfully obtained on a rough porous alumina substrate. Prior to the fabrication of palladium membrane, a poly(vinyl) alcohol (PVA) layer was first coated onto the porous substrate by dip-coating technique to improve its surface roughness and pore size. After deposition of palladium membrane on the PVA modified substrate, the polymer layer can be completely removed from the composite membrane by heat treatment. The microstructure of the palladium composite membrane was characterized in detail using SEM, EDXS and XRD analysis. Permeation measurements were carried out using H₂ and N₂ at temperatures of 623 K, 673 K, 723 K and 773 K. The results indicated that the hydrogen permeation flux of 0.238 mol m^?2 s^?1 with H₂ separation factor α(H₂/N₂) of 956 for the as-prepared palladium membrane was obtained at 773 K and 100 kPa. Furthermore, the good membrane stability was proven during the total operation time of 160 h at the temperature range of 623 K–773 K and gas exchange cycles of 30 between hydrogen and nitrogen at 723 K.     

Enhanced hydrogen permeance through graphene oxide membrane deposited on asymmetric spinel hollow fiber substrate

Membranes of graphene oxide (GO) present suitable application for hydrogen (H₂) purification. The deposition of a selective and high permeable GO membrane on a proper substrate is still a challenge. Here we applied the vacuum-assisted method to deposit a GO layer on asymmetric spinel (MgAl₂O₄) hollow fibers. The synthetized GO showed a nanosheeted morphological structure and a relative high degree of oxidation. The hollow fibers were produced with dolomite and alumina as the ceramic starting material and showed the desired asymmetric pore size distribution, in addition to suitable bending strength, 54.88 ± 4.25 MPa, and average surface roughness, 180 ± 8.2 nm. A continuous GO layer of 1.7 ± 0.2 μm was deposited onto the fiber outer surface. The composite MgAl₂O₄/GO membrane presented H₂ permeance of 8.2 ± 0.0 × 10^?7 mol s^?1 m^?2 Pa^?1 at room temperature (approximately 25 °C) and 0.3 MPa of transmembrane pressure. Ideal hydrogen/nitrogen and hydrogen/carbon dioxide selectivity values were of 3.3 ± 0.0 and 11.4 ± 0.1, respectively.     

PdAg/alumina membranes prepared by high power impulse magnetron sputtering for hydrogen separation

The development of hydrogen purification membranes that meet market demands such as high purity, dynamic hydrogen production even at small scale, and reduced costs is still an open question. With this view, the present study aims at developing, for the first time, a method based on high power impulse magnetron sputtering for the deposition of Pd77Ag23 (wt%) films onto porous alumina substrates to achieve composite membranes with high hydrogen permeability and stability. This technique allows the deposition of films also on complex geometries and can be easily scaled up, thus making this technology a potential candidate for preparing high performing membranes. Membranes made by stable and porous alumina supports and metallic, dense and crystalline Pd₇₇Ag₂₃ layers, from 3.5 μm to 17 μm thick, have been prepared and tested. The membranes showed good hydrogen permeability values, showing flux values up to a maximum of 0.62 mol_H2 m^?2 s^?1 at 450 °C and ΔP of 300 kPa. The resistance to hydrogen embrittlement and the chemical inertness to syngas were also demonstrated.     

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.     

Pre-activation of SBA-15 intermediate barriers with Pd nuclei to increase thermal and mechanical resistances of pore-plated Pd-membranes

Thermal and mechanical resistances of palladium composite membranes prepared by Electroless Pore-Plating (ELP-PP) and containing SBA-15 as intermediate layer were improved by doping the silica material with Pd nuclei before its incorporation on the composite membrane. Textural properties of synthesized SBA-15 materials (both raw and doped ones) were analyzed by XRD, N₂ adsorption-desorption at 77 K and TEM, while the main properties of the composite membrane were determined by SEM and gravimetric analyses. Moreover, membrane permeation tests were also carried out with pure gases, hydrogen and nitrogen, and binary mixtures of them at temperature of 400 °C and pressure driving forces in the range of 0.5–2.5 bar. The use of bare SBA-15 intermediate layer leads to the appearance of cracks on the Pd layer during permeation experiments at high temperature. In contrast, the use of Pd-doped SBA-15 particles avoids this problem, thus improving both thermal and mechanical resistances of the composite ELP-PP Pd-membrane. Following this preparation method, an estimated Pd thickness of 7.1 μm was obtained, reaching a hydrogen permeance of 3.81·10^?4 mol s^?1 m^?2 Pa^?0.5 and ensuring an ideal H₂/N₂ separation factor higher than 2550 at 400 °C.     

Influence of the type of siliceous material used as intermediate layer in the preparation of hydrogen selective palladium composite membranes over a porous stainless steel support

In this work, several composite membranes were prepared by Pd electroless plating over modified porous stainless steel tubes (PSS). The influence of different siliceous materials used as intermediate layers was analyzed in their hydrogen permeation properties. The addition of three intermediate siliceous layers over the external surface of PSS (amorphous silica, silicalite-1 and HMS) was employed to reduce both roughness and pore size of the commercial PSS supports. These modifications allow the deposition of a thinner and continuous layer of palladium by electroless plating deposition. The technique used to prepare these silica layers on the porous stainless steel tubes is based on a controlled dip-coating process starting from the precursor gel of each silica material. The composite membranes were characterized by SEM, AFM, XRD and FT-IR. Moreover they were tested in a gas permeation set-up to determine the hydrogen and nitrogen permeability and selectivity. Roughness and porosity of original PSS supports were reduced after the incorporation of all types of silica layers, mainly for silicalite-1. As a consequence, the palladium deposition by electroless plating was clearly influenced by the feature of the intermediate layer incorporated. A defect free thin palladium layer with a thickness of ca. 5 μm over the support modified with silicalite-1 was obtained, showing a permeance of 1.423·10⁻⁴ mol m⁻² s⁻¹ Pa^−0.5 and a complete ideal permselectivity of hydrogen.     

Effect of PBI-HFA surface treatments on Pd/PBI-HFA composite gas separation membranes

For pure hydrogen separation, palladium was deposited on surface-treated polybenzimidazole (PBI-HFA, 4,4′-(hexafluroisopropylidene)bis(benzoic acid)) via the vacuum electroless plating technique (VELP). Since the hydrophobic characteristics of the polymer surface restrict strong adhesion of Pd on it and cause the peel-off of Pd film, various surface treatments have been employed. To increase the number of Pd anchoring sites on the PBI-HFA surface, mechanical abrasion (polishing) was applied, and to increase the hydrophilicity of the PBI-HFA surface, wet-chemical and O₂ plasma treatment (dry etching) were used. The thickness and effective permeating area of the deposited Pd films on the PBI-HFA membranes were estimated to be in the range of 160–340 nm and 8.3 cm², respectively. Among the tested membranes, membranes with Pd layers deposited on O₂ plasma treated PBI-HFA surfaces had the most uniform microstructure and the least number of defects compared to the other membranes. Gas permeation experiments were performed as a function of temperature and pressure. The gases used in the permeation measurements were H₂, N₂, CO₂, and CO (99.9% purity). A Pd-O₂30 m membrane, fabricated by O₂ plasma surface treatment during 30 min, exhibited superior gas separation performance (H₂ permeability of 275.5 Barrer), and proved to be impermeable to carbon monoxide. Enhancement of H₂ permselectivity of Pd/PBI-HFA composite membrane treated by O₂ plasma shows promising hydrogen separation membrane.     

Diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd membrane deposited on porous stainless-steel support

In this study, we present an intermetallic diffusion barrier coating using a newly developed blowing coating method for a thermally stable Pd-based composite membrane on porous stainless steel (PSS). A tubular PSS sample with 1/2 inch (12.7 mm) in diameter and 450 mm in length was used for the support. The support was welded with a stainless-steel cap and a 450-mm-long stainless-steel tube for each end. Before the diffusion barrier coating, the large-sized entrance pores were gradually blocked with sub-micron (～500 nm) and nano (50–80 nm) yttria stabilized zirconia (YSZ). 8YSZ, i.e., 8wt.% YSZ, was used for the interdiffusion barrier material and dispersed on the surface of the pre-treated PSS using the blowing coating method. The blowing coating method has 4 steps: (i) spraying the 17 wt. % 8YSZ paste on the surface of the PSS tube, (ii) blowing the paste using compressed air, (iii) drying at room temperature, and (iv) heat treatment at 923 K for 2 h in air. Steps (i) and (ii) were repeated 3 times to have a ～240 nm thick 8YSZ layer. A thin palladium layer (～3 μm) was deposited on the pre-treated PSS using electroless plating, and the membrane stability was tested at 673–773 K for ～ 200 h. A hydrogen permeation flux of 9.86 × 10^?2 mol m^?2 s^?1 and an H₂/N₂ selectivity of 595 were obtained at 773 K and a transmembrane pressure difference of 20 kPa. The surface and cross-sectional SEM/EDX analysis confirmed that the 8YSZ layer sufficiently prevented the interdiffusion between Pd and PSS elements, such as Fe, Cr and Ni.     

Preparation of thin Pd membrane on porous stainless steel tubes modified by a two-step method

Thin Pd membranes for hydrogen filtration were deposited on modified porous stainless steel (PSS) tubes using an electroless plating technique. Alumina oxide (Al₂O₃) particles of two different sizes were subsequently used to modify the non-uniform pore distribution and the surface roughness of the PSS tubes. The principle of the modification was to use large Al₂O₃ particles (∼10 μm) to fill larger pores on the surface, and leave the smaller pores intact. Small Al₂O₃ particles (∼1 μm) were then used to further decrease the surface roughness. The detailed manufacturing steps of the Al₂O₃ modification were investigated and optimized to achieve a continuous dense Pd membrane with a minimum thickness of 4.4 μm on the modified PSS tubes. The highest hydrogen permeance of the membrane was 2.94 × 10⁻³ mol/m²-s-kPa^0.5 at 773 K, with a selectivity coefficient (H₂/He) of 1124 under a pressure difference of 800 kPa. In comparison, the thickness and hydrogen permeance of a dense Pd membrane on unmodified PSS tubes were 31.5 μm and 5.97 × 10⁻⁴ mol/m²-s-kPa^0.5, respectively, at 773 K under an 800 kPa pressure difference. The stability of the membranes at high temperatures was also investigated. The hydrogen permeation flux at 773 K was stable during a test period of 500 h. These results demonstrate that the two-step method modifies the surface of PSS tubes in a relatively simple way and results in thin, dense Pd membranes with high hydrogen permeance and good thermal stability.     

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.     

Deposition of an ultrathin palladium (Pd) coating on SAPO-34 membranes for enhanced H2/N2 separation

Hydrogen energy has attracted great attention due to its properties of high energy transferring efficiency and zero pollution emission. Zeolite membranes are promising candidates for H₂ separation because of their uniform, molecular-sized pores and high thermal and mechanical stabilities. However, thicker membranes or modification treatments are often necessary to eliminate the defects formed during synthesis and post calcination, leading to low gas permeance. Herein, we reported the deposition of an ultrathin palladium (Pd) coating on SAPO-34 membranes to improve H₂ separation performance. H₂/N₂ selectivity was greatly increased by deposition of an ultrathin Pd coating on SAPO-34 membranes, while maintaining similar H₂ permeance. This might be attributed to the dissociative adsorption and associative desorption of H₂ on Pd, as well as fast diffusion of H₂ through ultrathin Pd coating. We also noticed that excessive Pd deposition would lead to the formation of cracks on SAPO-34 membranes, leading to deteriorated membrane performance.     

Toward low-cost Pd/ceramic composite membranes for hydrogen separation: A case study on reuse of the recycled porous Al2O3 substrates in membrane fabrication

The development of hydrogen energy systems has placed a high demand on hydrogen-permeable membranes as compact hydrogen separators and purifiers. Although Pd/Ceramic composite membranes are particularly effective in this role, the high cost of these membranes has greatly limited their applications; this high cost stems largely from the use of expensive substrate material. This problem may be solved by substrate recycling and the use of lower cost substrates. As a case study, we employed expensive asymmetric microporous Al₂O₃ and low-cost macroporous symmetric Al₂O₃ as membrane substrates (average pore sizes are 0.2 and 3.3 μm, respectively). The palladium membranes were fabricated by electroless plating, and substrate recycling was carried out by palladium dissolution with a hot HNO₃ solution. The functional surface layer of the microporous Al₂O₃ was damaged during substrate recycling, and the reuse of the substrate led to poor membrane selectivity. With the assistance of pencil coating as a facile and environmentally benign surface treatment, the macroporous Al₂O₃ can be successfully utilized. Furthermore, the macroporous Al₂O₃ can be also recycled and reused as membrane substrate, yielding highly permeable, selective and stable palladium membranes. Consequently, the substrate cost can be further decreased, and the applications of this kind of membranes would expand.     

585 divacancy-defective germanene as a hydrogen separation membrane: A DFT study

As sustainable and clean energy, hydrogen is the most attractive and promising energy source in the future. Membrane separation is attractive due to its high hydrogen separation performance and low energy consumption. Van-der-Waals-corrected density functional theory (DFT) calculations are performed to investigate the hydrogen separation performance of 585 divacancy-defective germanene (585 germanene). It is found that the 585 germanene presents a surmountable energy barrier (0.34 eV) for hydrogen molecule passing through the membrane, and that membrane exhibits extremely high selectivity for H₂ molecules over CO, CO₂, N₂, CH₄ and H₂S molecules in a wide range of temperatures. Meanwhile, the hydrogen permeance of 585 germanene can reach 1.94 × 10^?7 mol s^?1 m^?2 Pa^?1 at the low limit temperature of methane reforming (at 450 K), which is higher than the industrially acceptable gas permeance. With high selectivity and permeance, the 585 germanene is a promising candidate for hydrogen separation.     

An improvement of the hydrogen permeability of C/Al2O3 membranes by palladium deposition into the pores

The development of compact hydrogen separator based on membrane technology is of key importance for hydrogen energy utilization, and the Pd-modified carbon membranes with enhanced hydrogen permeability were investigated in this work. The C/Al₂O₃ membranes were prepared by coating and carbonization of polyfurfuryl alcohol, then the palladium was introduced through impregnation–precipitation and colloid impregnation methods with a PdCl₂/HCl solution and a Pd(OH)₂ colloid as the palladium resources, and the reduction was carried out with a N₂H₄ solution. The resulting Pd/C/Al₂O₃ membranes were characterized by means of SEM, EDX, XRD, XPS and TEM, and their permeation performances were tested with H₂, CO₂, N₂ and CH₄ at 25 °C. Compared with the colloid impregnation method, the impregnation–precipitation is more effective in deposition of palladium clusters inside of the carbon layer, and this kind of Pd/C/Al₂O₃ membranes exhibits excellent hydrogen permeability and permselectivity. Best hydrogen permeance, 1.9 × 10⁻⁷ mol/m² s Pa, is observed at Pd/C = 0.1 wt/wt, and the corresponding H₂/N₂, H₂/CO₂ and H₂/CH₄ permselectivities are 275, 15 and 317, respectively.     

Effect of catalytic Pd coating on the hydrogen storage performances of ZrCo alloy by electroless plating method

The effects of Pd coating with different deposition concentration (PdCl₂ 0.2 g L^?1, 0.6 g L^?1, 1.0 g L^?1) on the surface morphology, microstructure and hydrogen storage performances of ZrCo alloy have been investigated. Results show that spherical Pd particles have been deposited on the surface of ZrCo alloy successfully, which transfer from sparse arrangement to continuous and compact film with increasing deposition concentration of PdCl₂. The hydriding kinetic property of all Pd coated alloys is improved compared with the bare alloy, which is due to the catalyst effect of Pd coating. The hydriding rate of the samples firstly increases and then decreases with increasing deposition concentration, which is closely related to the surface morphology and thickness of Pd coating. The hydriding kinetic property of the samples is greatly improved after 5 cycles, although Pd particles on the alloy surface peel off to some extent. This phenomenon indicates that the accumulated fresh surface during cycling makes a greater contribution to the improved hydriding kinetic property and the catalyst effect of Pd coating is weakened during cycling.     

High performance composite hollow fiber membranes for CO2/H2 and CO2/N2 separation

The search for a clean energy source as well as the reduction of CO₂ emissions to the atmosphere are important strategies to resolve the current energy shortage and global warming issues. We have demonstrated, for the first time, a Pebax/poly(dimethylsiloxane)/polyacrylonitrile (Pebax/PDMS/PAN) composite hollow fiber membrane not only can be used for flue gas treatment but also for hydrogen purification. The composite membranes display attractive gas separation performance with a CO₂ permeance of 481.5 GPU, CO₂/H₂ and CO₂/N₂ selectivity of 8.1 and 42.0, respectively. Minimizing the solution intrusion using the PDMS gutter layer is the key to achieving the high gas permeance while the interaction between poly(ethylene oxide) (PEO) and CO₂ accounts for the high selectivity. Effects of coating solution concentration and coating time on gas separation performance have been investigated and the results have been optimized. To the best of our knowledge, this is the first polymeric composite hollow fiber membrane for hydrogen purification. The attractive gas separation performance of the newly developed membranes may indicate good potential for industrial applications.     

On the long-term stability of Pd-membranes with TiO2 intermediate layers for H2 purification

This work addresses the use of TiO₂-based particles as an intermediate layer for reaching fully dense Pd-membranes by Electroless Pore-Plating for long-time hydrogen separation. Two different intermediate layers formed by raw and Pd-doped TiO₂ particles were considered. The estimated Pd-thickness of the composite membrane was reduced in half when the ceramic particles were doped with Pd nuclei before their incorporation onto the porous support by vacuum-assisted dip-coating. The real thickness of the top Pd-film was even lower (around 3 μm), as evidenced by the cross-section SEM images. However, a certain amount of palladium penetrates in some points of the porous structure of the support up to 50 μm in depth. In this manner, despite saving a noticeable amount of palladium during the membrane fabrication, lower H₂-permeance was found while permeating pure hydrogen from the inner to the outer surface of the membrane at 400 °C (3.55·10^?4 against 4.59·10^?4 mol m^?2 s^?1 Pa^?0.5). Certain concentration-polarization was found in the case of feeding binary H₂–N₂ mixtures for all the conditions, especially in the case of reaching the porous support before the Pd-film during the permeation process. Similarly, the effect of using sweep gas is more significant when applied on the side where the Pd-film is placed. Besides, both membranes showed good mechanical stability for around 200 h, obtaining a complete H₂/N₂ ideal separation factor for the entire set of experiments. At this point, this value decreased up to around 400 for the membrane prepared with raw TiO₂ particles as intermediate layer (TiO₂/Pd). At the same time, complete selectivity was maintained up to 1000 h in case of using doped TiO₂ particles (Pd–TiO₂/Pd). However, a specific decrease in the H₂-permeate flux was found while operating at 450 °C due to a possible alloy between palladium and titanium that is not formed at a lower temperature (400 °C). Therefore, Pd–TiO₂/Pd membranes prepared by Electroless Pore-Plating could be very attractive to be used under stable operation in either independent separators or membrane reactors in which moderate temperatures are required.