Metal Membrane Research Articles

Hydrogen Permeability of Composite Pd-Au/Pd-Cu Membranes and Methods for Their Preparation.

Thin Pd-40%Cu films were obtained via the classical melting and rolling method, magnetron sputtering, and modified with nanostructured functional coatings to intensify the process of hydrogen transportation. The films were modified by electrodeposition, according to the classical method of obtaining palladium black and "Pd-Au nanoflowers" with spherical and pentagonal particles, respectively. The experiment results demonstrated the highest catalytic activity (89.47 mA cm-2), good resistance to CO poisoning and long-term stability of Pd-40%Cu films with a pentagonal structured coating. The investigation of the developed membranes in the hydrogen transport processes in the temperature range of 25-300 °C also demonstrated high and stable fluxes of up to 475.28 mmol s-1 m-2 (deposited membranes) and 59.41 mmol s-1 m-2 (dense metal membranes), which were up to 1.5 higher, compared with membrane materials with classic niello. For all-metal modified membranes, the increase in flux was up to sevenfold, compared with a smooth membrane made of pure palladium, and for deposited films, this difference was manyfold. The membrane materials' selectivity was also high, up to 4419. The developed strategy for modifying membrane materials with functional coatings of a fundamentally new complex geometry can shed new light on the development and fabrication of durable and highly selective palladium-based membranes for gas steam reformers.

Effect of flux direction through supported metal membranes: Golden ratio as maximum benefit in pure hydrogen and concept of swap point in mixture

In this paper, the role of the flux direction in composite supported metal membranes for hydrogen purification is elucidated from both mathematical and physical point of view under pure-hydrogen and mixture conditions considering a double-layer supported Pd-based membrane. A definitive mathematical proof is given to demonstrate that, in pure-hydrogen conditions, if the metal layer obeys Sieverts’ law and the diffusion in the support is controlled by the Knudsen mechanism, the permeating flux measured by feeding hydrogen from the support to the metal layer is always higher than the flux measured in the opposite direction at the same operating conditions and for whatever values of layer permeances, extending the state-of-the-art findings of the specialized literature. As a further surprising result, it is found that the maximum benefit in switching the flux direction is equal to the mathematical number called golden ratio, this representing a notable general finding. Moreover, a partial generalization of these results is extended to other particular driving forces, which leads us to propose the non-demonstrated-yet general conjecture that the highest flux be the flux established from the layer with the highest driving force pressure exponent to the layer with the lowest one. Furthermore, observing that, in mixture conditions, the permeating flux from the support side is lower than the opposite one for a sufficiently high mixture composition of non-permeating species – especially in the presence of inhibiting species like CO – the novel concept of swap point is introduced, which represents the mixture composition at which the fluxes measured in the two directions are equal. The value of the swap point depends on membrane geometrical characteristics, temperature and non-permeating species. It is highlighted that the findings of the present work hold also for other types of composite ones (polymeric, ceramic, etc.) as well as for every physical system that whose behaviour can be modelled by a sequence of non-linear resistances.

Structure Design and Characterization of 3D Printing System of Thermal Battery Electrode Ink Film.

In this paper, a 3D printing system for a thermal battery electrode ink film is set up and investigated based on the on-demand microdroplet ejection technology. The optimal structural dimensions of the spray chamber and metal membrane of the micronozzle are determined via simulation analysis. The workflow and functional requirements of the printing system are set up. The printing system includes a pretreatment system, piezoelectric micronozzle, motion control system, piezoelectric drive system, sealing system, and liquid conveying system. Different printing parameters are compared to obtain optimized printing parameters, which can be attributed to the optimal pattern of the film. The feasibility and controllability of 3D printing methods are verified by printing tests. The size and output speed of the droplets can be controlled by adjusting the amplitude and frequency of the driving waveform acting on the piezoelectric actuator. So, the required shape and thickness of the film can be achieved. An ink film in terms of nozzle diameter = 0.6 mm, printing height = 8 mm, wiring width = 1 mm, input voltage = 3 V and square wave signal frequency = 35 Hz can be achieved. The electrochemical performance of thin-film electrodes is crucial in thermal batteries. The voltage of the thermal battery reaches its peak and tends to flatten out at around 100 s when using this printed film. The electrical performance of the thermal batteries using the printed thin films is found to be stable. This stabilized voltage makes it applicable to thermal batteries.

Measured noise levels beneath type B flat metal roof assemblies during rainfall

Flat metal roof assemblies are common in steel building design. Since they can produce high levels of rainfall generated noise, quiet roof assemblies are desirable over noise sensitive spaces. To determine the relative effects of assembly variations, a pair of fixtures were constructed to measure the noise levels beneath 2 x 4 ft sections of selected roof assemblies subjected to rainfall. Each test item was assembled from precut 2 x 4 ft sections of Type B metal roof (with or without a concrete layer), cover boards, and insulation, membrane and ballast as required. The fixtures were equipped with tipping buckets to measure rainfall rate. A microphone located inside each box and connected to a digital recorder, picked up ambient noise, rainfall generated roof assembly noise and the tipping bucket signal. To calibrate the recordings, the sound pressure level of the tipping bucket signal at the recording microphone was measured before testing. Recordings were analyzed to calculate indicated octave band sound power levels versus rainfall rate for the various tested roof assemblies.

Parametric Study of the Vacuum Permeator for the Tritium Extraction eXperiment

Tritium breeding is a critical component of any self-sustaining future fusion reactor. The liquid-metal eutectic PbLi is of particular interest as a tritium breeder material due to its favorable thermophysical and neutronic properties. One of the several remaining challenges facing PbLi breeder blankets is the need to design and validate a highly efficient tritium extraction system. The vacuum permeator is a promising extraction concept that utilizes tritium permeation through a highly permeable metal membrane. The Tritium Extraction eXperiment (TEX) is a forced-convection PbLi loop constructed to investigate tritium extraction from PbLi with vacuum permeators. Accurate thermal-hydraulic and tritium transport models are required to establish appropriate test matrices, predict experiment outcomes, and analyze data. However, the hydrogen transport properties of PbLi and permeator materials have large uncertainties. A database is collected and a parametric analysis is conducted on the effect of hydrogen transport material properties, including diffusivity of H in PbLi and the permeator, solubility of H in PbLi and the permeator, and the permeator surface recombination constant, on the expected tritium extraction efficiency for a vacuum permeator installed in TEX. Herein, we observe that the solubility of H in PbLi and the permeator and the recombination constant of the permeator have the largest effect on extraction efficiency.

Contemporary avenues of the Hydrogen industry: Opportunities and challenges in the eco-friendly approach

Hydrogen (H2) is a possible energy transporter and feedstock for energy decarbonization, transportation, and chemical sectors while reducing global warming's consequences. The predominant commercial method for producing H2 today is steam methane reforming (SMR). However, there is still room for development in process intensification, energy optimization, and environmental concerns related to CO2 emissions. Reactors using metallic membranes (MRs) can handle both problems. Compared to traditional reactors, MRs operates at substantially lower pressures and temperatures. As a result, capital and operational costs may be significantly cheaper than traditional reactors. Furthermore, metallic membranes (MMs), particularly Pd and its alloys, naturally permit only H2 permeability, enabling the production of a stream with a purity of up to 99.999%. This review describes several methods for H2 production based on the energy sources utilized. SRM with CO2 capture and storage (CCUS), pyrolysis of methane, and water electrolysis are all investigated as process technologies. A debate based on a color code was also created to classify the purity of H2 generation. Although producing H2 using fossil fuels is presently the least expensive method, green H2 generation has the potential to become an affordable alternative in the future. From 2030 onward, green H2 is anticipated to be less costly than blue hydrogen. Green H2 is more expensive than fossil-based H2 since it uses more energy. Blue H2 has several tempting qualities, but the CCUS technology is pricey, and blue H2 contains carbon. At this time, almost 80–95% of CO2 can be stored and captured by the CCUS technology. Nanomaterials are becoming more significant in solving problems with H2 generation and storage. Sustainable nanoparticles, such as photocatalysts and bio-derived particles, have been emphasized for H2 synthesis. New directions in H2 synthesis and nanomaterials for H2 storage have also been discussed. Further, an overview of the H2 value chain is provided at the end, emphasizing the financial implications and outlook for 2050, i.e., carbon-free H2 and zero-emission H2.

Electrochemical Surface Treatment for Tailored Porous Structures

Plasma electrolytic oxidation (PEO) was used to establish a porous metal oxide layer on various titanium and zirconium workpieces in the form of wires, porous tubes, and 3D-printed structures. The ultimate goal of the work was to create a layer with the desired characteristics over a catalyst support or metal membrane structures to improve the performance of the targeted high-temperature catalytic conversion or separation applications. In doing so, it was ensured that the PEO-treated layer could provide the desired morphology, thickness, and porosity needed for the final processing step, which is usually a conventional coating method. This addresses the limitations of ceramic structures, including their mechanical resistance, thermal resistance, and conductivity, and their potential for being functionalized and utilized for high-temperature applications. The entire experimental run was carried out using a 2 kilowatt (maximum output) AC-power source with a maximum current limit of 6.5 Ampere while applying a constant potential (potentiostatic) and monitoring the current fluctuation. Depending on the surface areas of the PEO-treated samples, the applied potential ranged from 200 V to 260 V. The surface features of the fresh and PEO-treated composites, including their morphology and phases, were studied using conventional characterization techniques such as SEM, EDX, and XRD. The time required to observe the spark discharge was shortened by tuning the PEO parameters, such as gradually increasing the applied potential. This, in turn, allowed for longer surface treatment and, eventually, more control over the surface texture. The EDX analysis of the elemental composition of the PEO-treated surface indicated that the contribution of the electrolyte-deposited components increases when increasing the voltage and is accompanied by an increase in the extent of oxidation. The titanium samples displayed relatively intense discharges, especially in comparison to the Zirconium wires. The PEO-treated samples were coated via standard wet-coating techniques.

Collectable Single Pure-Pd Metal Membrane with High Strength and Flexibility Prepared through Electroplating for Hydrogen Purification

Among the various film preparation methods, electroplating is one of the simplest and most economical methods. However, it is challenging to collect a dense single Pd film through plating, owing to the accumulation of stress in the film during the process. Therefore, the characteristics of a single plated film have not been clearly identified, although pure Pd is widely used in metallic-hydrogen-purification membranes. In this study, stress concentration in film during preparation was reduced by optimizing the plating process, and a dense single flat film was successfully collected. No impurities were detected. Thus, a high-purity Pd film was prepared. Its surface texture was found to be significantly different from that of the rolled film, and several approximately 5 μm sized aggregates were observed on the surface. The plated film is reported to have mechanical properties superior to those of the rolled film, with twice the displacement and four times the breaking point strength. The hydrogen permeabilities of the plated film (5.4 × 10−9–1.1 × 10−8 mol·m−1·s−1·Pa−1/2 at 250–450 °C) were comparable to those of the rolled and reported films, indicating that the surface texture does not have a strong effect on hydrogen permeability. The results of this study promote the practical use of Pd-based membranes through electroplating.

Novel methods to induce complex coacervation using dual fluid nozzle and metal membranes: Part II – Use of metal membrane technology to induce complex coacervation

In this follow up study, which is the extension of our previous work on the use of metal membranes for production of ginger oil emulsions with engineered droplet size (part I), we continue the exploration of membrane technology for production of complex coacervates. In this paper (part II) we introduced a novel method to induce multi core complex coacervation using metal membrane technology - which has been most used for drop-by-drop emulsification. Gelatin (4% and 10% w/w) and ginger oil (gelatin to ginger oil ratio 1:1) emulsions were produced using the high shear homogenization followed by injection through the metal membranes to induce complex coacervation using gum Arabic at pH 3.5 using a dispersion cell. The capsules (coacervates) produced using metal membrane (with 24 µm pore diameter) had spherical shape with diameters between 53 and 72 µm. Encapsulation efficiency ranged between 61% and 93% while the encapsulation yield varied from 15% to 90%, being significantly higher for emulsions with 4% (w/w) of gelatin. Complex coacervation by metal membrane was compared with coacervation induced by atomization and batch stirring. The methods discussed in this study can be potentially used in encapsulation of both lipophilic and hydrophilic compounds. Finally considering encapsulation properties and the possibility of engineering the capsules size, the use of membrane technology is a promising new configuration to induce complex coacervation, with real possibilities to allow scale up of the process of complex coacervation.

Measured noise levels beneath type B flat metal roof assemblies during rainfall

Flat metal roof assemblies are common in steel building design. Since they can produce high levels of rainfall generated noise, quiet roof assemblies are desirable over noise sensitive spaces. To determine the relative effects of design variations, a pair of fixtures were constructed to measure the noise levels beneath 2 × 4 ft sections of selected roof assemblies subjected to rainfall. Each test item was assembled from precut 2 × 4 ft sections of type B metal roof (with or without a concrete layer), cover boards, and insulation, membrane and ballast as required. The fixtures included a tipping bucket to measure rainfall rate. A microphone located inside each fixture and connected to a digital recorder, picked up ambient noise, rainfall generated roof assembly noise, and the tipping bucket signal. To calibrate the recordings, the sound pressure level of the tipping bucket signal was measured at the recording microphone before testing. Recordings are analyzed to calculate indicated octave band sound power levels versus rainfall rate for the various tested roof assemblies. Promising variations for further study are given.

Relationship between hydrogen permeability and the physical-chemical characteristics of metal alloy membranes

Due to the vast compositional range of advanced hydrogen-selective alloys, quantitative and well-targeted development are extremely challenging. This paper examines a wide range of bond properties related to high-H2 permeability metal membranes. An investigation of the relationships between hydrogen (H2) permeability and physical-chemical characteristics, namely, atomic radius difference (δ), mixed entropy (ΔS), electronegativity difference (Δχ), and valence electron concentration (VEC), was proposed using a data set of 170H2 permeation experiments at 673 K collected from about 70 scientific literature references regarding Pd-, Ni-, Nb-, Ti-, V-, and Zr-based binary, ternary, or more complex alloy membranes. The following conclusions can be drawn from the selected experimental data collected in the literature: It seems that for the metal alloy membranes, the H2 permeation properties have a close correlation to bond parameters. On the whole, the H2 permeability increased as the VEC decreased, regardless of alloy membranes and other characteristics. If light VEC metals are considered to consist of any metal having a relatively low valence electron concentration, light VEC alloys are seen to be the greatest options for achieving high H2 permeability. Our physical-chemical criterion, which is based on the bond properties of metal alloy membranes, can be utilized to both create new H2-selective alloy membranes and improve the efficiency of currently studied membranes.

Interconnected Metallic Membrane Enabled by MXene Inks Toward High‐Rate Anode and High‐Voltage Cathode for Li‐Ion Batteries

AbstractThe ever‐increasing popularity of smart electronics demands advanced Li‐ion batteries capable of charging faster and storing more energy, which in turn stimulates the innovation of electrode additives. Developing single‐phase conductive networks featuring excellent mechanical strength/integrity coupled with efficient electron transport and durability at high‐voltage operation should maximize the rate capability and energy density, however, this has proven to be quite challenging. Herein, it is shown that a 2D titanium carbide (known as MXene) metallic membrane can be used as single‐phase interconnected conductive binder for commercial Li‐ion battery anode (i.e., Li4Ti5O12) and high‐voltage cathodes (i.e., Ni0.8Mn0.1Co0.1O2). Electrodes are fabricated directly by slurry‐casting of MXene aqueous inks composited with active materials without any other additives or solvents. The interconnected metallic MXene membrane ensures fast charge transport and provides good durability, demonstrating excellent rate performance in the Li//Li4Ti5O12cell (90 mAh g−1at 45 C) and high reversible capacity (154 mAh g−1at 0.2 C/0.5 C) in Li//Ni0.8Mn0.1Co0.1O2cell coupled with high‐voltage operation (4.3 V vs Li/Li+). The LTO//NMC full cell demonstrates promising cycling stability, maintaining capacity retention of 101.4% after 200 cycles at 4.25 V (vs Li/Li+) operation. This work provides insights into the rational design of binder‐free electrodes toward acceptable cyclability and high‐power density Li‐ion batteries.

Pure metallic nanofibrillar membrane for high-performance electrostatic air filtration with antimicrobial and reusable characteristics

We introduce a metallic high-efficiency particulate air (HEPA) filter based on a Cu nanofiber membrane, which grasps particulate matters physically and electrostatically. The filter also shows excellent antimicrobial property and reusability.

Surface/interfacial transport through pores control desalination mechanisms in 2D carbon-based membranes.

The shortage of freshwater is a critical concern for contemporary society, and reverse osmosis desalination technology has gathered considerable attention as a potential solution to this problem. It has been recognized that the desalination process involving water flow through angstrom-sized pores has tremendous potential. However, it is challenging to obtain angstrom-sized pore structures with internal mass transfer and surface/interface properties matching the application conditions. Herein, a two-dimensional (2D) zeolite-like carbon structure (Carzeo-ANG) was constructed with unique angstrom-sized pores in the zeolite structure; then, the surface/interfacial transport behavior and percolation effect of the Carzeo-ANG desalination membrane were evaluated by density functional theory (DFT) calculations and classical molecular dynamics. The first-principles calculations in density functional theory were implemented through the Vienna ab initio simulation package (VASP), which is a commercial package for the simulation of carbon-based materials. The results show that Carzeo-ANG is periodically distributed with angstrom-sized pores (effective diameter = 5.4 Å) of dodecacyclic carbon rings, which ensure structural stability while maintaining sufficient mechanical strength. The remarkable salt-ion adsorption properties and mass transfer activity combined with the reasonable density distribution and free energy barrier for water molecules endow the membrane with superior desalination ability. At the pressure of 80 MPa, the rejection efficiency of Cl- and Na+ were 100% and 96.25%, and the membrane could achieve a water flux of 132.71 L cm-2 day-1 MPa-1. Moreover, the interconnected electronic structure of Carzeo-ANG imparts a self-cleaning effect.

First principles study of V/Pd interface interactions and their hydrogen absorption properties

Hydrogen permeation through vanadium/palladium (V/Pd) metal composite membranes is an effective and practical method of separating hydrogen from gas mixtures. In order to gain an insight into the relation between the interfacial structure and hydrogen adsorption/diffusion properties of the catalytic Pd layer bonded to the metal membrane, and then improve the ability of the alloy membrane to purify hydrogen, the first principle based on the density functional theory is used to study the hydrogen adsorption/diffusion behavior at the V/Pd metal composite membrane interface. The results show that because the charge density at the V/Pd interface increases with the V/Pd bonding increasing, the dissolution energy of hydrogen atom (H) increases with it approaching to the interface, and it has the highest dissolution energy near the V/Pd interface (0.567 eV). Hydrogen migration energy barrier calculations show that compared with the maximum energy barrier for horizontal diffusion of H along the V/Pd interface (0.64 eV), the H vertical V/Pd interface energy barrier (0.56 eV) is small, thus H tends to migrate vertically V/Pd interface and diffuse from the Pd layer to the V substrate side. As the hydrogen solvation energy of the Pd layer at the V/Pd interface (0.238 eV) is higher than that on the V membrane side (–0.165 eV), H will gather on the V film side of the interface, which is easy to cause hydrogen to be embrittled. Calculations of Pd/Fe doping of the V matrix show that comparing with the undoped energy barrier (0.56 eV), Pd/Fe doping can significantly reduce the maximum energy barrier (0.45 eV/0.54 eV) in the diffusion path of the interface, which is favorable for hydrogen permeation and diffusion. And the doped interface can inhibit the interdiffusion of V layer and catalytic Pd layer to a certain extent, which improves the structural stability of the composite film.

Free-standing and binder-free nickel polymeric nanofiber membrane for electrocatalytic oxidation of ethanol in alkaline solution

In-situ chemical reduction technique was exploited to fabricate free-standing and binder-free active nanocatalyst materials for direct ethanol fuel cells using nickel nanoparticles onto polyvinylidenefluoride-co-hexafluoropropylene membrane [Ni/PVdF-HFP]. Homogeneously distributed nickel nanoparticles with face-centered cubic structure were observed onto smooth membrane surfaces. Cyclic voltammetric measurements indicated the enhanced activity of Ni/PVdF-HFP membrane for oxidizing the alcohol molecules in NaOH solution. The measured oxidation current density increased with increasing the added ethanol concentration into the supporting electrolyte up to 0.64 M. Some kinetic parameters were calculated such as the charge transfer coefficient (α), Tafel slope and exchange current density values to record 0.468, 369 mV dec−1 and 1.28 μA cm−2, respectively. The three dimensional nanostructure of these fabricated metallic membranes and the increased number of their active voids could provide largely exposed surface areas for adsorbed alcohol molecules. The good stability of nickel nanoparticles onto PVdF-HFP membrane surface with minimum leaching level during prolonged ethanol oxidation in alkaline solution can offer unique possibilities for utilizing these polymeric electrocatalyst structures for energy production applications.

Ultra-hydrophilic layered titanate nanosheet-based nanofiltration membrane with ultrafast water transport for low energy consumption desalination

Nanofiltration (NF) membranes have significant applications to solve global water scarcity issues. An ultra-hydrophilic inorganic NF membrane was fabricated using ultra-hydrophilic layered titanate H1.07Ti1.73O4·nH2O nanosheets (HTO-ns), which exhibits high selectivity for desalination and small molecule separations while maintained an ultrafast water transport at low operating pressure. This membrane would be a low-energy consumption NF membrane. To fabricate the HTO-ns membrane, a straightforward technique, namely, the self-adjusting membrane thickness process (SAMTP), was developed by the restacking process of negatively charged HTO-ns with cations on a porous polytetrafluoroethylene (PTFE) substrate. A large-scaled high-quality HTO-ns membrane can be fabricated on a PTFE substrate surface-modified with a silane coupling agent of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and Cu2+ adsorption. There are two kinds of nanochannels for water transport through the membrane, namely, interlayer nanochannels and nanosheet edges chink nanochannels. The excellent separation performances were contributed by the interlayer nanochannels and Donnan exclusion effect of the negatively charged HTO-ns. The SAMTP technique developed in this study could also be applied simply to fabricate other metal oxide nanosheet membranes, which would open a new avenue to the high-performance ultra-hydrophilic inorganic nanosheet-based membranes for low energy consumption separation processes.

Investigation of droplet size distribution for vibrating mesh atomizers

Vibrating mesh atomizers (VMA) are increasing in demand for various aerosol applications due to their ability to generate uniform droplets. Currently there are two types of VMA (metallic membranes and silicon membranes). High uniformity and control of small droplet sizes are the basic requirements for many aerosol applications, for which ultrasonic or VMA are employed. However, there is limited research on understanding the droplet size distribution of different types of atomizers. In this study three ultrasonic aerosol generators were investigated initially: traditional high frequency ultrasonic, metallic VMA, and Si-based microelectromechanical systems VMA. The initial objective was to compare these devices with respect to droplet size distribution and mechanism of action. The primary goal was to systematically study and compare the performance of the two types of VMA based on droplet distribution and volumetric median diameter (VMD) using liquids with different physiochemical properties. Size distribution of the droplet produced from the metallic VMA had twice the span compared to silicon VMA for fluids with viscosity <2 cP. The metallic VMA also resulted in an increase in VMD as the viscosity increased, whereas the Si VMA did not illustrate any significant increase in VMD. The silicon-based VMA demonstrated a 4–15x increase in fine particle fraction control compared to metallic VMA. The results demonstrate that silicon based VMA has narrower droplet distribution with more uniform droplet size and lower span compared to metallic VMA.

Novel metallic stainless-steel mesh-supported conductive membrane and its performance in the electro-filtration process

In this study, we demonstrate the fabrication of a thoroughly metallic electro-conductive membrane by using simple filtration to uniformly coat AgNWs dispersion through stainless steel (SUS)-mesh, which functions both as filter and a flexible conductive substrate. The as-prepared AgNWs networks layer on the SUS-mesh was further strengthened by electroplating Ag layers (P-SUS membrane); exhibiting an overall electrical conductivity of 9.2 × 104 S/m, which is up to 42 times greater than the conductivity of pristine SUS-mesh. The P-SUS membrane exhibited adequate physical durability against chemical and mechanical stresses under prolonged filtration, and high pure water flux of 534 ± 54 LMH/bar. This electro-membrane displayed the anticipated flux recovery in harvesting microalgae (Chlorella sp. HS-2) when filtration was done with the membrane used as a cathode: micro-sized bubbles, generated from the cathodic membrane, functioned to detach the foulants and recover the relative flux to a significant level. The P-SUS membrane indeed possesses necessary traits that the polymer-support membrane lacks, in terms of not only electrical conductivity and mechanical strength but also filtration performance with anti-fouling capability, all of which are of necessity to be considered workable electroconductive membrane.

Ultrathin metal-mesh Janus membranes with nanostructure-enhanced hydrophobicity for high-efficiency fog harvesting

Fog harvesting has been reckoned to be one of the most facile and economical approaches to alleviating the ever-increasing global water scarcity . Janus membranes, especially metallic ones, outperform other fog collectors in terms of fog harvesting efficiencies , and they are the selection for sustainable water production as passive devices. However, there is a lack of metallic Janus membranes with ultrasmall feature sizes due to the limitation of the laser ablation fabrication method , which restrains parameter optimization for highly efficient fog collectors. In this work, photolithography , electroplating , and nanoimprint lithography processes are employed to enable ultrasmall membrane thickness and nanopatterning on the membrane surface . A 4-μm-thick ultrathin hierarchical metal-mesh Janus membrane with a pitch of 60 μm is fabricated, which achieves a record-high water collection rate of 233 mg cm −2 ·min −1 with nanostructure-enhanced hydrophobicity . The morphology of the membrane is characterized by scanning electron microscopy, while the fog collection process is observed under a high-speed camera and a microscope. Experimental measurement and finite-element numerical modeling unveil that a smaller membrane thickness and a more hydrophobic water-collecting surface contribute to higher water collection rates by accelerating water transport and reducing water re-evaporation. • Photolithography and electroplating replace laser ablation for metallic JM fabrication. • Metallic JMs with unprecedented thickness down to 4 μm are fabricated. • Nanopatterning on JMs changes surface wettability and boosts WCR. • A record-high WCR of 233 mg cm −2 ·min −1 is achieved.