Search Results (50)

Perovskite mixed proton–electron hydrogen-permeable membranes have been widely applied in the field of membrane separation due to their 100% selectivity for hydrogen separation. La_5.5WO_11.25-δ-La_0.87Sr_0.13CrO_3-δ (LWO-LSF) four-channel hollow fiber membranes were prepared by the phase inversion and sintering technique using a one-step thermal processing (OSTP) approach. The effects of temperature, feed gas concentration, sweep gas flow, permeation mode, and water vapor on hydrogen flux were systematically investigated. At 900 °C, the hydrogen permeation flux of 50% H₂/N₂ feed from the shell side to the lumen side was 0.613 mL·min⁻¹·cm⁻², which was 62.59% higher than that from the lumen side to the shell side. The enhanced hydrogen permeation performance is attributed to the lower gas mass transfer resistance under shell-side feeding. Under humidified conditions on the sweep side, the hydrogen flux increased by an additional 3.42%. The presence of water vapor increased the number of proton carriers, effectively enhancing proton–electron-coupled transport and thereby increasing the hydrogen permeation flux. Full article

The high-temperature proton ceramic membranes with simultaneous separation of hydrogen and oxygen exhibit promising applications in the catalytic conversion field. However, their separation performance often relies on external electrical circuits, which limits practical application. To overcome this limitation, doping strategies have emerged as a viable approach to develop triple-conducting (H⁺/e⁻/O²⁻) membranes for simultaneous hydrogen and oxygen separation in non-electrochemical mode. In this study, honeycomb-structured hollow fiber membranes were fabricated, and the effects of varying Fe³⁺ and Y³⁺ doping concentrations on hydrogen and oxygen permeation fluxes were systematically investigated. At the Fe³⁺ doping level of 0.2 mol, the oxygen permeation flux of 0.692 mL min⁻¹ cm⁻² in BaCe_0.6Zr_0.2Fe_0.2O_3−δ (BCZF) was achieved at 1000 °C, while the hydrogen permeation flux was 0.201 mL min⁻¹ cm⁻². The BaCe_0.55 Fe_0.05Zr_0.2Y_0.2O_3−δ (Fe-BCZY) hollow fiber membrane can enhance the hydrogen permeation flux by 75% at 1000 °C. Furthermore, during the simultaneous permeation of hydrogen and oxygen, a 1.7-fold enhancement in hydrogen permeation performance was achieved for the Fe-BZCY hollow fiber membrane at 1000 °C, and with oxygen permeation flux of 1.76 mL min⁻¹ cm⁻² at the same temperature. More significantly, a hydrogen permeation flux of 0.34 mL min⁻¹ cm⁻² can be achieved at 700 °C under simultaneous hydrogen and oxygen permeation, which is favorable for the application of membrane reactors in catalytic reactions. Full article

Oxygen transport membranes (OTMs) have gained a lot of attention for their application in different innovative fields, but the development of new materials able to combine high oxygen permeability and good chemical stability is crucial to boost the exploitation of such membrane-based technologies. Perovskite oxides are widely studied as mixed ionic-electronic conductors for the realization of OTMs. In this article, we focus on _Sr1-xCa_xTi_0.8Fe_0.2O_3-ẟ (SCTF) perovskites and investigate the effect of Ca content on the A-site of the permeation properties, both in single-phase SCTF membranes and in dual-phase membranes obtained by combining SCTF and the ionic conductor Ce_0.8Gd_0.2O₂ (CGO). In single-phase samples, we observed that the substitution of 40% Ca preserves the permeation performances of the non-substituted SrTi_0.8Fe_0.2O_3−ẟ membrane while allowing for a substantial decrease in the sintering temperature, thus facilitating membrane manufacturing. In dual-phase membranes, the increase in the Ca content in the perovskite causes an increase in grain size. The permeation is, at least partially, controlled by the kinetics of the surface exchange reactions. This limitation can be overcome by the addition of an activation layer; however, the permeance of activated CGO-SCTF membranes still remains lower compared to the single-phase parent perovskitic membranes. Full article

A comprehensive literature review highlights how the nature of active metals, support materials, promoters, and synthesis methods influences catalytic performance, with particular attention to ruthenium-based catalysts as the current benchmark. Kinetic models are presented to describe the reaction pathway and predict catalyst behavior. Various reactor configurations, including fixed-bed, membrane, catalytic membrane, perovskite-based, and microreactors, are evaluated in terms of their suitability for ammonia decomposition. While ruthenium remains the benchmark catalyst, alternative transition metals such as iron, nickel, and cobalt have also been investigated, although they typically require higher operating temperatures (≥500 °C) to achieve comparable conversion levels. At the industrial scale, catalyst development must balance performance with cost. Inexpensive and scalable materials (e.g., MgO, Al₂O₃, CaO, K, Na) and simple preparation techniques (e.g., wet impregnation, incipient wetness) may offer lower performance than more advanced systems but are often favored for practical implementation. From a reactor engineering standpoint, membrane reactors emerge as the most promising technology for combining catalytic reaction and product separation in a single unit operation. This review provides a critical overview of current advances in ammonia decomposition for hydrogen production, offering insights into both catalytic materials and reactor design strategies for sustainable energy applications. Full article

Currently, the trade-off between oxygen permeation flux and structural stability in conventional perovskite oxides restricts the practical application of oxygen permeable membranes. In this study, a high-entropy design was applied to the B-site of BSCF matrix materials, resulting in the successful synthesis of a high-entropy perovskite, Ba_0.5Sr_0.5Co_0.71Fe_0.2Ta_0.03Ni_0.03Zr_0.03O_3−δ. The crystal structure, microstructure, and elemental composition of the material were systematically characterized and analyzed. Theoretical analysis and experimental characterization confirm that the material exhibits a stable single-phase high-entropy perovskite oxide structure. Under He as the sweep gas, the membrane achieved an oxygen permeation flux of 1.28 mL·cm⁻²·min⁻¹ and operated stably for over 100 h (1 mm thick, 900 °C). In a 20% CO₂/He atmosphere, the flux remained above 0.92 mL·cm⁻²·min⁻¹ for over 100 h, demonstrating good CO₂ tolerance. Notably, when the sweep gas is returned to the pure He atmosphere, the oxygen permeation flux fully recovers to 1.28 mL·cm⁻²·min⁻¹, with no evidence of leakage. These findings indicate that the proposed B-site doping strategy can break the trade-off between oxygen permeability and structural stability in conventional perovskite membranes. This advancement supports the industrialization of oxygen permeable membranes and offers valuable theoretical guidance for the design of high-performance perovskite materials. Full article

Gel-polymer electrolytes offer a promising route toward safer and more stable sodium-ion batteries, but conventional polymer systems often suffer from low ionic conductivity and limited voltage stability. In this study, we developed composite GPEs by embedding methylammonium lead chloride (CH₃NH₃PbCl₃, MPCl) into a UV-crosslinked ethoxylated trimethylolpropane triacrylate (ETPTA) matrix, with sodium alginate (SA) as an ionic conduction enhancer. Three types of membranes—GPE-P, GPE-El, and GPE-Eh—were synthesized and systematically compared. Among them, the high-MPCl formulation (GPE-Eh) exhibited the best performance, achieving a high ionic conductivity of 2.14 × 10⁻³ S·cm⁻¹, a sodium-ion transference number of 0.66, and a wide electrochemical window of approximately 4.9 V vs. Na⁺/Na. In symmetric Na|GPE|Na cells, GPE-Eh enabled stable sodium plating/stripping for over 600 h with low polarization. In Na|GPE|NVP cells, it delivered a high capacity retention of ~79% after 500 cycles and recovered ~89% of its initial capacity after high-rate cycling. These findings demonstrate that the perovskite–polymer composite structure significantly improves ion transport, interfacial stability, and electrochemical durability, offering a viable path for the development of next-generation quasi-solid-state sodium-ion batteries. Full article

Anion-doped perovskite membranes with a hollow fiber geometry have excellent oxygen separation performance. However, during the fabrication process of hollow fiber membranes, soaking the precursor in deionized water leads to elemental dissolution, especially anion dissolution. To prevent metal and anion element dissolution, an improved one-step thermal processing approach was proposed in which saturated solutions were used as internal and external coagulation baths, effectively controlling the stoichiometric ratio. Compared with using deionized water as internal and external coagulation baths, using a fluorine-containing saturated solution increased the oxygen flux of the membrane by 21% at 900 °C. The oxygen permeability of the fluorine-doped oxide membrane reached 6 mL cm⁻² min⁻¹ at 900 °C, with an oxygen flux exceeding 1 mL cm⁻² min⁻¹ at 700 °C, meeting commercial oxygen separation membrane standards. Anion doping and stability enhancement strategies could further advance the development and practical use of oxygen separation membranes. Full article

Ceramic proton conductors have the potential to lower the operating temperature of solid oxide cells (SOCs) to the intermediate temperature range of 400–600 °C. This is attributed to their superior ionic conductivity compared to oxide ion conductors under these conditions. However, prominent proton-conducting materials, such as yttrium-doped barium cerates and zirconates with specified compositions like BaCe_1−xY_xO_3−δ (BCY), BaZr_1−xY_xO_3−δ (BZY), and Ba(Ce,Zr)_1−yY_yO_3−δ (BCZY), face significant challenges in achieving dense electrolyte membranes. It is suggested that the incorporation of transition and alkali metal oxides as sintering additives can induce liquid phase sintering (LPS), offering an efficient method to facilitate the densification of these proton-conducting ceramics. However, current research underscores that incorporating these sintering additives may lead to adverse secondary effects on the ionic transport properties of these materials since the concentration and mobility of protonic defects in a perovskite are highly sensitive to symmetry change. Such a drop in ionic conductivity, specifically proton transference, can adversely affect the overall performance of cells. The extent of variation in the proton conductivity of the perovskite BCZY depends on the type and concentration of the sintering aid, the nature of the sintering aid precursors used, the incorporation technique, and the sintering profile. This review provides a synopsis of various potential sintering techniques, explores the influence of diverse sintering additives, and evaluates their effects on the densification, ionic transport, and electrochemical properties of BCZY. We also report the performance of most of these combinations in an actual test environment (fuel cell or electrolysis mode) and comparison with BCZY. Full article

High-entropy perovskite materials (HEPMs), characterized by their multi-element composition and highly disordered structure, can incorporate multiple rare earth elements at the A-site, producing perovskites with enhanced CO₂ resistance, making them stay high performance and structurally stable in the CO₂ atmosphere. However, this modification may result in reduced oxygen permeability. In this study, we investigated La_0.2Pr_0.2Nd_0.2Ba_0.2Sr_0.2Co_0.8Fe_0.2O_3-δ (L_0.2M_1.8) high-entropy perovskite materials, focusing on enhancing their oxygen permeability in both air and CO₂ atmospheres through strategic design modifications at the B-sites and A/B-sites. We prepared Ni-substituted La_0.2Pr_0.2Nd_0.2Ba_0.2Sr_0.2Co_0.7Fe_0.2Ni_0.1O_3-δ (L_0.2M_1.7N_0.1) HEPMs by introducing Ni elements at the B-site, and further innovatively introduced A-site defects to prepare La_0.2Pr_0.2Nd_0.2Ba_0.2Sr_0.2Co_0.7Fe_0.2Ni_0.1O_3-δ (L_0.1M_1.7N_0.1) materials. In a pure CO₂ atmosphere, the oxygen permeation flux of the L_0.1M_1.7N_0.1 membrane can reach 0.29 mL·cm⁻²·min⁻¹. Notably, the L_0.1M_1.7N_0.1 membrane maintained a good perovskite structure after stability tests extending up to 120 h under 20% CO₂/80% He atmosphere. These findings suggest that A-site-defect high-entropy perovskites hold great promise for applications in CO₂ capture, storage, and utilization. Full article

Oxygen and hydrogen mobility are among the important characteristics for the operation of solid oxide fuel cells, permselective membranes and many other electrochemical devices. This, along with other characteristics, enables a high-power density in solid oxide fuel cells due to reducing the electrolyte resistance and enabling the electrode processes to not be limited by the electrode-electrolyte-gas phase triple-phase boundary, as well as providing high oxygen or hydrogen permeation fluxes for membranes due to a high ambipolar conductivity. This work focuses on the oxygen and hydrogen diffusion of mixed ionic (oxide ionic or/and protonic)–electronic conducting materials for these devices, and its role in their performance. The main laws of bulk diffusion and surface exchange are highlighted. Isotope exchange techniques allow us to study these processes in detail. Ionic transport properties of conventional and state-of-the-art materials including perovskites, Ruddlesden–Popper phases, fluorites, pyrochlores, composites, etc., are reviewed. Full article

SrZrO₃-based perovskites are promising proton-conducting membranes for use in fuel and electrolysis cells, sensors, hydrogen separators, etc., because they combine good proton conductivity with excellent chemical stability. In the present research, the effect of Lu-doping on microstructure, phase composition, and electrical conductivity of SrZr_1−xLuxO_3−δ (x = 0–0.10) was investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and impedance spectroscopy. Dense ceramic samples were obtained by the solution combustion synthesis and possessed an orthorhombic perovskite-type structure. The solubility limit of Lu was revealed to lie between x = 0.03 and 0.05. The conductivity of SrZr_1−xLu_xO_3−δ increases strongly with the addition of Lu at x < 0.05 and just slightly changes at x > 0.05. The rise of the water vapor partial pressure results in an increase in the conductivity of SrZr_1−xLuxO_3−δ ceramics, which confirms their hydration ability and significant contribution of protonic defects to the charge transfer. The highest conductivity was achieved at x = 0.10 (10 mS cm^–1 at 700 °C, wet air, pH₂O = 0.61 kPa). The conductivity behavior was discussed in terms of the defect formation model, taking into account the improvement in ceramic sintering at high lutetium concentrations. Full article

Perovskite membranes have gained considerable attention in gas separation and production due to their unique properties such as high selectivity and permeability towards various gases. These membranes are composed of perovskite oxides, which have a crystalline structure that can be tailored to enhance gas separation performance. In oxygen enrichment, perovskite membranes are employed to separate oxygen from air, which is then utilized in a variety of applications such as combustion and medical devices. Moreover, perovskite membranes are investigated for carbon capture applications to reduce greenhouse gas emissions. Further, perovskite membranes are employed in hydrogen production, where they aid in the separation of hydrogen from other gases such as methane and carbon dioxide. This process is essential in the production of clean hydrogen fuel for various applications such as fuel cells and transportation. This paper provides a review on the utilization and role of perovskite membranes in various gas applications, including oxygen enrichment, carbon capture, and hydrogen production. Full article

Simultaneous syngas and pure hydrogen production through partial oxidation of methane and water splitting, respectively, were demonstrated by using mixed ionic–electronic conductors. Tubular ceramic membranes prepared from La_0.5Sr_0.5FeO₃ perovskite were successfully utilized in a 10 M lab scale reactor by applying a radial arrangement. The supply of methane to the middle area of the reaction zone was shown to provide a uniform distribution of the chemical load along the tubes’ length. A steady flow of steam feeding the inner part of the membranes was used as oxidative media. A described configuration was found to be favorable to maintaining oxygen permeability values exceeding 1.1 mL∙cm^–2∙min^–1 and long-term stability of related functional characteristics. Methane’s partial oxidation reaction assisted by 10%Ni@Al₂O₃ catalyst proceeded with selectivity values above 90% and conversion of almost 100%. The transition from a laboratory model of a reactor operating on one tubular membrane to a ten-tube one resulted in no losses in the specific performance. The optimized supply of gaseous fuel opens up the possibility of scaling up the reaction zone and creating a promising prototype of a multitubular reaction zone with a simplified sealing procedure. Full article

Inverted perovskite solar cells with a p-i-n configuration have attracted considerable attention from the research community because of their simple design, insignificant hysteresis, improved operational stability, and low-temperature fabrication technology. However, this type of device is still lagging behind the classical n-i-p perovskite solar cells in terms of its power conversion efficiency. The performance of p-i-n perovskite solar cells can be increased using appropriate charge transport and buffer interlayers inserted between the main electron transport layer and top metal electrode. In this study, we addressed this challenge by designing a series of tin and germanium coordination complexes with redox-active ligands as promising interlayers for perovskite solar cells. The obtained compounds were characterized by X-ray single-crystal diffraction and/or NMR spectroscopy, and their optical and electrochemical properties were thoroughly studied. The efficiency of perovskite solar cells was improved from a reference value of 16.4% to 18.0–18.6%, using optimized interlayers of the tin complexes with salicylimine (1) or 2,3-dihydroxynaphthalene (2) ligands, and the germanium complex with the 2,3-dihydroxyphenazine ligand (4). The IR s-SNOM mapping revealed that the best-performing interlayers form uniform and pinhole-free coatings atop the PC₆₁BM electron-transport layer, which improves the charge extraction to the top metal electrode. The obtained results feature the potential of using tin and germanium complexes as prospective materials for improving the performance of perovskite solar cells. Full article

Formamidinium lead bromide (FAPbBr₃) nanocrystals have emerged as a powerful platform for optoelectronic applications due to their pure green photoluminescence (PL). However, their low colloidal stability under storage and operation reduces the potential use of FAPbBr₃ perovskite nanocrystals (PeNCs) in various applications. In this study, we prepared the poly(L–lactic acid) (PLLA) nanofibrous membrane embedded with FAPbBr₃ perovskite nanocrystals by electrospinning the perovskite and PLLA precursor solution. This is a simple and low-cost technique for the direct confinement of nano-sized functional materials in the continuous polymer nanofibres. PLLA as a polymer matrix provided a high surface framework to fully encapsulate the perovskite NCs. In addition, we found that FAPbBr₃ PeNCs crystallize spontaneously inside the PLLA nanofibre. The resultant PLLA-FAPbBr₃ nanofibrous membranes were stable and remained in the water for about 45 days without any evident decomposition. The results of this research support the idea of new possibilities for the production of air-stable FAPbBr₃ PeNCs by forming a composite with PLLA polymer. The authors believe this study is a new milestone in the development of highly stable metal halide perovskite-based nanofibres, which allow for potential use in lasers, waveguides, and flexible energy harvesters. Full article