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Mixed ionic-electronic conducting (MIEC) membranes have gained
growing interest recently for various promising environmental and energy
applications, such as H2 and O2 production, CO2 reduction, O2 and H2
separation, CO2 separation, membrane reactors for production of chemicals,
cathode development for solid oxide fuel cells, solar-driven evaporati...
Citations
... Nickel (Ni)-based catalysts particularly exhibit exceptional catalytic performance and can further reduce the CDM temperature to between 450 and 550 °C [22][23][24], at which the catalytic reactor system can ideally be coupled with an H 2 -permeable membrane to optimize the reaction yield, CH 4 conversion, and energy integration efficiency [25,26]. The higher CDM initial catalytic activity and lower operating temperature requirements for Ni-based catalysts relative to their iron and cobalt-based counterparts are due to high carbon solubility and rapid carbon diffusion rate on the Ni nanoparticles [27]. ...
Catalytic methane (CH4) decomposition (CDM) offers a direct pathway for hydrogen (H2) gas production and valuable carbon nanotube (CNT) synthesis. However, the stability of this gas-to-solid reaction is hindered by limitations in CNT growth and reactor volume constraints. Departing beyond conventional nanopowder catalysts, we introduce basalt fiber-supported Ni/LTA catalysts that feature COx-free H2 generation and up to 3.7 times longer CDM reaction times, delivering an H2 production rate of 3.1 mol gNi⁻¹ h⁻¹ over 22 h at 500 °C, surpassing Ni/LTA nanopowder counterparts. The basalt fiber catalysts exhibit uniform and robust CNT growth, along with sustained and stable H2 generation lasting up to three times longer relative to traditional CDM catalysts that deactivate within 10 h as reported in the literature. Integration of the flexible basalt fiber catalysts into an H2-permeable LTA-Pd membrane reactor further enhances the reaction time by 36% and CH4 conversion by 40%, achieving up to 45% CH4 conversion over 27 h, surpassing expected equilibrium conversion rates. The excellent catalytic stability of the 10 wt% Ni/LTA basalt fiber catalyst is additionally showcased through multiple reduction-800 °C CDM reaction-CO2 regeneration cycles. This transformative study propels the development of functional catalyst materials, revolutionizing thermocatalytic processes.
Graphical abstract
A basalt fiber-supported LTA zeolite-based nickel catalyst advances methane decomposition, yielding COx-free hydrogen, multi-wall carbon nanotubes, and extensive reaction time.
... Oxygen-transporting membranes (OTMs) based on mixed ionic-electronic conductors (MIECs) have attracted considerable attention in promising applications, such as in the production of oxygen-enriched air [1], in the selective oxidation of methane and ethane [2], as cathode material in solid oxide fuel cells [3], and also in rechargeable lithium-air batteries [4]. Currently, perovskite-type MIECs containing Ba 2+ and/ or Sr 2+ cations exhibit immense oxygen permeability due to the high amount of oxygen vacancies [5][6][7]. Unfortunately, perovskite materials such as Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) or doped SrCo 0.8 Fe 0.2 O 3−δ are vulnerable when operated in CO 2 -containing atmosphere because alkaline earth carbonate layers can form on the surface of the membranes, blocking the oxygen flux and thus restrict their potential uses [8][9][10]. In contrast, La 2 NiO 4+δ (LNO) possesses a high long-term chemical stability in CO 2 atmosphere [11,12]. ...
Textured La2NiO4+δ membranes were fabricated by pressureless sintering in air using uniaxially pressed powder mixtures consisting of fine-grained equiaxial La2NiO4+δ matrix particles and plate-like La2NiO4+δ template particles in varying mass ratios. The template particles, obtained by molten-flux synthesis, were aligned perpendicular to the pressing direction. Subsequent sintering resulted in ceramic membranes with enhanced texturing along the crystallographic c-axis of La2NiO4+δ. X-ray diffraction patterns revealed a direct relationship: The higher the fraction of template particles in the ceramics, the more pronounced the c-axis texturing. The Lotgering orientation factor, calculated from the X-ray diffraction patterns, also demonstrated that an increasing proportion of the template particles in the ceramic materials led to stronger (00l) reflections. Additionally, the texturing degree in selected membranes was quantified by measuring pole figures. Scanning electron micrographs of the La2NiO4+δ samples with a small amount of template particles showed some individual plate-like grains well integrated into the matrix. Membrane porosity was observed to increase with higher quantities of template particles utilized. This was supported by measuring the membrane density using the Archimedes method: The larger the proportion of template particles in the ceramics, the lower the sample density. Besides, the presence of lanthanum, nickel, and oxygen in the membranes was confirmed by energy-dispersive X-ray spectroscopy. Finally, the effect of texturing on the oxygen permeation performance of the La2NiO4+δ membranes, in which the template particles are arranged along their c-axis, parallel to the oxygen flux direction, was investigated. The results indicated a reduction in oxygen flux as the level of c-axis texturing increased.
Graphical abstract
... The current technological development of MIEC membranes allows their use in applications such as H2 production, O2 separation, CO2 reduction, membrane reactors, and material development for fuel cell cathodes and solid oxide electrolyzers for synthetic fuel processes [11,12]. Numerous contributions and studies have focused on the production of syngas via co-electrolysis to generate synthetic fuels. ...
... Kriegel [31] investigated the competitiveness of MIEC membrane plants for commercial oxygen production, providing a unique perspective on their potential. Chen et al. [11] presented a roadmap for sustainable mixed ionic-electronic conducting membranes, contributing to the advancement of membrane technologies. Catalán-Martínez et al. [32] characterized oxygen transport phenomena on Ba0.5Sr0.5Co0.8Fe0.2O3−δ ...
... Theoretically, perovskite-type MIEC ceramic membranes can separate oxygen with 100% selectivity, offering an efficient and simplified method for O2 production. The MIEC membrane-based separation method can reduce energy consumption by 60% and significantly cut production costs by approximately 35% compared to current cryogenic technology [11]. Figure 1 illustrates a diagram of the integrated heat recovery and oxygen extraction system. ...
The current state of mixed ionic–electronic conducting ceramic membrane technology presents significant advancements with potential applications in various fields including solid oxide electrolyzers, fuel cells, hydrogen production, CO2 reduction, and membrane reactors for chemical production and oxygen separation. Particularly in oxygen separation applications, optimal conditions closely align with the conditions of oxygen-rich air streams emitted from the anode of solid oxide co-electrolyzers. This paper describes and analyzes a novel integrated heat recovery system based on mixed ionic–electronic conducting membranes. The system operates in two stages: firstly, oxygen is separated from the anode output stream using mixed ionic–electronic conducting membranes aided by a vacuum system, followed by the heat recovery process. Upon oxygen separation, the swept gas stream is recirculated at temperatures near thermoneutral conditions, resulting in performance improvements at both cell and system levels. Additionally, an oxygen stream is generated for various applications. An Aspen HYSYS® model has been developed to calculate heat and material balances, demonstrating the efficiency enhancements of the proposed system configuration.
... Membrane materials are widely used in applications such as water purication, 7 petrochemical rening, 8 pharmaceutical manufacturing, 9 mining, 10 construction, 11,12 warfare, 13 apparel, 14 electronics, 15 forensics, 16,17 medical applications, 18 and space exploration. 19 They are at the core of ltration and separation processes and impact various industries. ...
Membrane science and technology has the potential to considerably contribute to most of the United Nations' sustainable development goals. This technology has diverse applications, including in mining, water treatment, healthcare, and space. Membranes directly impact the three pillars of sustainability, namely, the economy, environment, and society. Membrane materials and processes must be developed in line with green chemistry and engineering principles. Herein, the 12 principles of green membrane materials and processes are introduced to encourage and guide scientists, engineers, and practitioners to design, explore, and implement membranes efficiently and sustainably. Moreover, the membrane waste management hierarchy is introduced, and the importance of each principle and priorities for future research are established.
... In their dense form, in which complex oxides exhibit a pronounced mixed ionic-electronic conductivity, these materials can also be used as oxygen permeation membranes [29][30][31][32]. The characterization of oxygen permeable membranes is often helpful in determining oxygen ionic conductivity against the background of high electronic conductivity (the latter for PBNx varies in the range of 60-100 S cm − 1 between 100 and 900 • C [24]). ...
Layered nickelates, Ln2NiO4+δ, are promising electrode materials for many electrochemical applications, including solid oxide fuel cells and electrolysis cells. Although Ln2NiO4+δ has been extensively modified by various doping strategies to tune its functional properties, the partial substitution of Ln3+ with Ba2+ remains among the least studied routes. At the same time, such substitution is found to be favorable when Ln2NiO4+δ materials are used for protonic ceramic electrochemical cells based on Ba-containing proton-conducting electrolytes (i.e., BaCeO3, BaZrO3, Ba(Ce,Zr)O3). In this work, which is the third part of a systematic study, Pr2–xBaxNiO4+δ materials are used as electrodes for a proton ceramic fuel cell and as oxygen permeable membranes. The oxygen permeation experiments confirm that the compositions with x = 0.2 and 0.3 prevail over x = 0 and 0.1 in terms of their oxygen-ionic conductivity, while the electrochemical cell characterizations confirm the high electrochemical activity of the Pr1.8Ba0.2NiO4+δ electrode in both fuel-cell- and electrolysis-cell modes. Our research thus confirms that a Ba-doping strategy is highly promising for designing new Ln2NiO4+δ-based phases, simultaneously offering good chemical and thermal compatibility with state-of-the-art proton-conducting electrolytes and high electrochemical performance.
... In their dense form, in which complex oxides exhibit a pronounced mixed ionic-electronic conductivity, these materials can also be used as oxygen permeation membranes [29][30][31][32]. The characterization of oxygen permeable membranes is often helpful in determining oxygen ionic conductivity against the background of high electronic conductivity (the latter for PBNx varies in the range of 60-100 S cm − 1 between 100 and 900 • C [24]). ...
Searching for suitable materials for symmetrical solid oxide fuel cells is an essential direction in modern high-temperature electrochemistry. One promising option for symmetrical electrode materials is a family of Fe-based complex oxides, which have high mixed ionic and electronic conductivity. This study focuses on the synthesis and thorough evaluation of the Pr1–xBaxFeO3–δ (x = 0.4, 0.5, 0.6) materials as symmetrical electrodes for proton ceramic electrochemical cells. The functional properties of these phases, both in powder and ceramic forms, are investigated for the first time under oxidizing and reducing conditions. The obtained results indicate that a low Ba-content is preferable for achieving high redox stability, low thermal expansion, and high conductivity of ferrite-based perovskites. However, Ba-enriched samples exhibit the lowest polarization resistance, particularly in reducing atmospheres. This may be due to the easier exsolution of Fe-metallic particles with high electrocatalytic activity. Therefore, a certain compromise needs to be achieved considering the obtained experimental data in a complex form. This work provides a basis for designing symmetrical electrodes by offering comprehensive information on the functional properties of ferrites in both oxidizing and reducing conditions.
... These are comprised of a material that is conductive for oxygen ions and electronic charge carriers (electrons, defect electrons). The OTMs are referred to as mixed ionic electronic conductor (MIEC) membranes or ion transport membranes (ITMs), with the driving force for O 2 permeation created by the difference of partial pressures of oxygen (pO 2 ) determined by a gradient of oxygen vacancies across the membrane [53]. The oxygen ion transport mechanism is a thermally activated process; therefore, such membranes work at high temperatures, typically 800 • C -1300 • C. The post-plasma region of a MW plasma falls well within this temperature range [9]. ...
We explored the potential of plasma-based In-Situ Resource Utilization (ISRU) for Mars through the conversion of Martian atmosphere (~96% CO 2 , 2% N 2 , and 2% Ar) into life-sustaining chemicals. As the Martian surface pressure is about 1% of the Earth's surface pressure, it is an ideal environment for plasma-based gas conversion using microwave reactors. At 1000 W and 10 Ln/min (normal liters per minute), we produced ~76 g/h of O 2 and ~3 g/h of NO x using a 2.45 GHz waveguided reactor at 25 mbar, which is ~3.5 times Mars ambient pressure. The energy cost required to produce O 2 was ~0.013 kWh/g, which is very promising compared to recently concluded MOXIE experiments on the Mars surface. This marks a crucial step towards realizing the extension of human exploration.
... Membrane materials are widely used in applications such as water purication, 7 petrochemical rening, 8 pharmaceutical manufacturing, 9 mining, 10 construction, 11,12 warfare, 13 apparel, 14 electronics, 15 forensics, 16,17 medical applications, 18 and space exploration. 19 They are at the core of ltration and separation processes and impact various industries. ...
... 17 The permeation fluxes through these membranes are determined by the oxygen partial pressure difference and are a strong function of the membrane's temperature, with temperatures above 700°C being usually required. 18,19 The removal of O 2 using a plasma-membrane reactor, wherein the heat supplied by the plasma facilitates oxygen permeation, has been first demonstrated by Chen et al. 15 In this work, a La 0.6 Ca 0.4 Co 0.5 Fe 0.5 O 3−δ (LCCF6455) membrane was exposed to a CO 2 plasma driven by 2.45 GHz microwaves at atmospheric pressure. Further investigations with the same plasma-membrane reactor have been performed by Buck et al. with a La 0.6 Ca 0.4 Co 0.8 Fe 0.2 O 3−δ (LCCF6482) hollow fiber membrane. ...
The removal of oxygen from the effluent of a CO2 plasma using multiple perovskite La0.6Ca0.4Co0.5Fe0.5O3−δ hollow fiber membranes is reported. A microwave plasma torch featuring a water-cooled 5 mm nozzle operated at quasi-atmospheric pressure was used. This configuration yielded moderate CO2 conversions (≥20%) and sufficiently large temperatures to thermally activate up to 21 membranes distributed over various rows in the plasma effluent. The CO2 conversion was only slightly affected by the microwave power and remained unchanged, regardless of the number of membranes placed in the effluent. The amount of permeated oxygen increased both with the microwave power and with the number of membranes, since the former yields hotter effluents (>700°C) and the latter increases the surface area available for permeation. The largest O2 permeation flow was obtained for 21 membranes and a microwave power of 2550 W: ≃42 sccm or ≃4.8% of the available O2. These correspond to the highest performances of such a plasma-membrane reactor thus far. The permeated O2 flow was also affected by the argon flow purging the membranes. Using one membrane, the flow of extracted oxygen decreased for an Ar flow below 250 sccm, while the opposite was observed with 10 membranes, yielding an increase in the oxygen flow from ≃25 to ≃28 sccm upon decreasing the total Ar flow below 2500 sccm. Key aspects that must be tackled for the design and testing of a plasma-membrane prototype that aims to remove O2 beyond 90% are discussed.
... Hollow fiber membranes, known for their high oxygen permeability, have been extensively investigated and implemented in oxygen transport dual-functional membrane reactors. 2 The coupling of reactions can be achieved by the dissociation of oxygen-containing gases (e.g., H 2 O, CO 2 , and NO x ) in combination with other oxidative processes like the POM as shown in Figure 1. The development of suitable OTM materials tailored to specific applications necessitates varying specifications. ...
... Although photocatalysis using solar energy has been extensively investigated, the low efficiency of these semiconductor catalysts has limited their practical applications. 1,2 Alternative methods, such as electrolysis or direct thermal water decomposition, have been explored. 1,2 However, conventional reactors face challenges due to the low equilibrium constant for H 2 F I G U R E 1 Schematic diagram of oxygen transport dual-functional membrane reactor for coupling dissociation of oxygen-containing gases (e.g., H 2 O, CO 2 , and NO x ) with an oxidative process (e.g., partial oxidation of methane [POM] and oxidative coupling of methane [OCM]). ...
... Some researchers are using waste H 2 to get pure H 2 by condensing unreacted steam. 1,2,7,14 Many other researchers are more interested in coupling with an oxidative process reaction to get more useful products from the membrane reactors. 1,7 The H 2 production rate is strongly associated with the oxygen consumption rate in the permeate side for fast oxygen extraction in the water dissociation side. ...
The integration of membrane separation processes with chemical reactions through oxygen transport dual‐functional membrane reactors has attracted significant attention due to the potential for process intensification, which also can create a synergy between the two units. This approach holds promise for promoting green chemistry principles by reducing energy consumption and environmental pollution. Despite its potential, a comprehensive review of recent advancements exploring the full potential of oxygen transport dual‐functional membrane reactors (coupling two distinct reactions) in enhancing membrane performance is currently lacking. To address this gap, this perspective article presents various concepts and principles of oxygen transport dual‐functional membrane reactors and provides an overview of recent advances and applications. Additionally, the challenges and opportunities for future research to enhance the efficiency of the process toward industrialization are discussed and highlighted. These include developing novel oxygen transport membrane materials, optimizing membrane engineering, innovating membrane reactor design, and exploring new applications and reaction mechanisms.
