Metal–Organic Framework Materials for the Separation and Purification of Light Hydrocarbons

The separation and purification of light hydrocarbons (LHs) mixtures is one of the most significantly important but energy demanding processes in the petrochemical industry. As an alternative technology to energy intensive traditional separation methods, such as distillation, absorption, extraction, etc., adsorptive separation using selective solid adsorbents could potentially not only lower energy cost but also offer higher efficiency. The need to develop solid materials for the efficiently selective adsorption of LHs molecules, under mild conditions, is therefore of paramount importance and urgency. Metal–organic frameworks (MOFs), emerging as a relatively new class of porous organic–inorganic hybrid materials, have shown promise for addressing this challenging task due to their unparalleled features. Herein, recent advances of using MOFs as separating agents for the separation and purification of LHs, including the purification of CH₄, and the separations of alkynes/alkenes, alkanes/alkenes, C₅–C₆–C₇ normal/isoalkanes, and C₈ alkylaromatics, are summarized. The relationships among the structural and compositional features of the newly synthesized MOF materials and their separation properties and mechanisms are highlighted. Finally, the existing challenges and possible research directions related to the further exploration of porous MOFs in this very active field are also discussed.     

质子陶瓷膜燃料电池电解质材料的研究进展

质子陶瓷膜燃料电池作为固体氧化物燃料电池低温工作的一种有效途径而受到了广泛的关注.本文介绍了以高温质子导体为电解质的质子陶瓷膜燃料电池的进展,指出传统质子陶瓷膜燃料电池较差的化学稳定性是阻碍其发展的重要因素.重点评述了近期化学稳定性好的高温质子导体电解质材料的发展以及新的掺杂体系对于经典BaCeO3基质子导体在化学稳定性、电导率和烧结活性等方面的作用,分析了高温质子导体作为电解质材料在质子陶瓷膜燃料电池发展中存在的问题和发展的方向.     

Microporous Organic Materials for Membrane‐Based Gas Separation

Membrane materials with excellent selectivity and high permeability are crucial to efficient membrane gas separation. Microporous organic materials have evolved as an alternative candidate for fabricating membranes due to their inherent attributes, such as permanent porosity, high surface area, and good processability. Herein, a unique pore‐chemistry concept for the designed synthesis of microporous organic membranes, with an emphasis on the relationship between pore structures and membrane performances, is introduced. The latest advances in microporous organic materials for potential membrane application in gas separation of H₂, CO₂, O₂, and other industrially relevant gases are summarized. Representative examples of the recent progress in highly selective and permeable membranes are highlighted with some fundamental analyses from pore characteristics, followed by a brief perspective on future research directions.     

Preparation and proton conductivity of poly(vinylidene fluoride)/layered double hydroxide nanocomposite gel electrolytes

Layered double hydroxide (LDH) was synthesized in the presence of sodium dodecyl sulfate. X-ray diffraction (XRD) and infrared spectrum revealed that dodecyl sulfate (DS) anions were successfully intercalated into the interlayers of LDH. Poly(vinylidene fluoride)/LDH nanocomposite membranes were prepared by mixing the DS intercalated LDH with poly(vinylidene fluoride) (PVDF) in N,N’′-dimethylformamide solution followed by the solvent evaporation. The nanocomposite membranes were further swollen with a H₃PO₄ solution in ethylene carbonate-propylene carbonate to obtain the proton conducting nanocomposite gel electrolytes. XRD and transmission electron microscope results showed that LDH particles were well-dispersed in the polymer matrix and partially intercalated by polymer chains. The proton conductivity was highly enhanced in the nanocomposite gel electrolyte systems. In the case of the nanocomposite gel electrolyte containing 7.40 wt.% LDH, the proton conductivity increased by about 2.5 times compared to pure PVDF gel electrolyte.     

A novel preparation method for porous noble metal/ceramic catalytic membranes

Adsorption at liquid/solid interface has been explored to prepare catalytically active ceramic membranes. Boehmite sol maintains its dynamic stability in the pH range of 3.5–4. Adsorption of metal salt on the sol particles can only be performed in the above pH range, but the adsorption can still be optimized by proper choice of ligand. Therefore, the effect of the ligands (NH₃, Cl^–, EDTA) on the adsorption of the noble metal ions (Pd(II), Pt(II), Pt(IV) and Rh(III)) as a function of pH on -Al₂O₃ particles was studied. Thus the noble metal complexes which can significantly adsorb in the above pH range were found. Using the complexes, the noble metal ion modified boehmite sols were synthesized. Then by the sol-gel process, the porous noble metal/ceramic cataytic membranes were prepared. The membranes were further characterized by N₂ adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and SEM-WDX (wave dispersion of X-ray). The H₂ and N₂ permeation through these membranes at elevated temperatures was also measured. Based on the above experiments, the novel technique can produce the mesoporous catalytically active ceramic membranes without any defects and with a uniform dispersion of the active materials in the coating.     

Proton conductive membranes based on silicotungstic acid/silica and polybenzimidazole

Membranes formed by polybenzimidazole and silicotungstic acid supported on silica have been prepared. The membranes were characterized in order to evaluate their proton conduction, mechanical stability and structural characteristics. Silica produced a beneficial effect on proton conduction of the membranes. The membranes with 50 wt.% of SiWA–SiO₂/PBI was mechanically stable and gave proton conductivity of 1.2×10⁻³ S cm⁻¹ at 160°C and 100% relative humidity. All the materials prepared had amorphous structure.     

Chitosan-Linked Dual-Sulfonate COF Nanosheet Proton Exchange Membrane with High Robustness and Conductivity

2D materials that can provide long-range ordered channels in thin-film form are highly desirable for proton exchange membranes (PEMs). Covalent organic framework nanosheets (CONs) are promising 2D materials possessing intrinsic porosity and high processability. However, the potential of CONs in PEMs is limited by loose sheet stacking and interfacial grain boundary, which lead to unsatisfied mechanical property and discontinuous conduction pathway. Herein, chitosan (CS), a natural polymer with rich  NH₂ groups, is designed as the linker of dual-sulfonate CONs (CON-2(SO₃H)) to obtain CON-2(SO₃H)-based membrane. Ultrathin CON-2(SO₃H) with high crystallinity and large lateral size is synthesized at water–octanoic acid interface. The high flexibility of CS chains and their electrostatic interactions with  SO₃H groups of CON-2(SO₃H) enable effective connection of CON-2(SO₃H), thus endowing membrane dense structure and exceptional stability. The stacked CON-2(SO₃H) constructs regular hydrophilic nanochannels containing high-density  SO₃H groups, and the electrostatic interactions between CON-2(SO₃H) and CS form interfacial acid–base pairs transfer channels. Consequently, CON-2(SO₃H)@CS membrane simultaneously achieves superior proton conductivity of 353 mS cm⁻¹ (under 80 °C hydrated condition) and tensile strength of 95 MPa. This work highlights the advantages of proton-conducting porous CON-2(SO₃H) in advanced PEMs and paves a way in fabricating robust CON-based membranes for various applications.     

Metal–Organic Frameworks as a Versatile Platform for Proton Conductors

Metal–organic frameworks (MOFs) are an intriguing type of crystalline porous materials that can be readily built from metal ions or clusters and organic linkers. Recently, MOF materials, featuring high surface areas, rich structural tunability, and functional pore surfaces, which can accommodate a variety of guest molecules as proton carriers and to systemically regulate the proton concentration and mobility within the available space, have attracted tremendous attention for their roles as solid electrolytes in fuel cells. Recent advances in MOFs as a versatile platform for proton conduction in the field of humidity condition proton-conduction, anhydrous atmosphere proton-conduction, single-crystal proton-conduction, and including MOF-based membranes for fuel cells, are summarized and highlighted. Furthermore, the challenges, future trends, and prospects of MOF materials for solid electrolytes are also discussed.     

Inorganic lead-based halide perovskites: From fundamental properties to photovoltaic applications

Compared with organic–inorganic hybrid halide perovskites (OIHPs), inorganic cesium lead halide perovskites (CsPbX₃) possess superior intrinsic stability for high temperatures and are considered one of the most attractive research hotspots in the perovskite photovoltaic (PV) field in the past several years. The PCE of CsPbX₃ inorganic perovskite solar cells (IPSCs) has increased from 2.9% in 2015 to more than 20% with excellent stability. There are still many on-going studies on the properties of perovskite materials and their applications in PV technology, thereby needing a thorough understanding. Here, the progress of inorganic perovskites is systematically introduced, including the fundamental properties of CsPbX₃ materials and CsPbX₃-based PV devices. The origins of stability and instability of CsPbX₃ and defects in CsPbX₃ are discussed. CsPbI₃-, CsPbI₂Br-, CsPbIBr₂- and CsPbBr₃-based PV devices and performance are comprehensively reviewed. The stabilization methods and mechanism for the photoactive phases of inorganic perovskites with low bandgap are emphasized. Reported strategies to boost the performance of CsPbX₃-based IPSCs are summarized. In the end, the potential of inorganic perovskites is evaluated, which opens up new prospects for the commercialization of IPSCs.     

燃料电池用高温质子交换膜的研究进展

燃料电池是一种高效的清洁能源技术,可缓解当今社会面临的能源和环境问题。质子交换膜燃料电池是一种重要的燃料电池类型,质子交换膜是其关键组件,起到传导质子、隔绝电子和阴阳两极的反应物的作用。质子交换膜燃料电池在低温下存在许多难以解决的问题,升高工作温度可以解决这些问题。因此需要开发高温低湿度下工作的膜材料。本文综述了高温质子交换膜的主要类型、制备与改性方法和质子传导机制,指出质子导体掺杂的聚苯并咪唑(PBI)类膜材料在高温低湿度下作为质子交换膜适用的巨大潜力,并探讨了复合PBI高温质子交换膜的制备、掺杂的质子导体类型和性能提升方法。最后本文归纳了高温质子交换膜面临的挑战,并指出了该类材料未来的研究方向,如设计合成新型质子导体、改善PBI抗氧化稳定性、调控膜微观结构来提升性能和开发新型聚合物电解质。     

Three-dimensional hydrogel frameworks for high-temperature proton exchange membrane fuel cells

With an aim of enhancing anhydrous proton conductivity and phosphoric acid (H₃PO₄) retention, we here report the employment of three-dimensional (3D) polyacrylamide-graft-chitosan (PAAm-g-CS) frameworks as supporters to load enormous H₃PO₄. Intrinsic microporous structure can seal H₃PO₄ molecules in the interconnected 3D frameworks of PAAm-g-CS matrix during a dehydration process. The hydrogel membranes are thoroughly characterized by morphology observation, structural analysis, swelling kinetics, proton-conducting performances as well as electrochemical behaviors. Results show that H₃PO₄ loading and therefore proton conductivity of the resultant PEMs are dramatically improved by employing PAAm-g-CS matrix in comparison with H₃PO₄-doped polybenzimidazole membranes. The highest H₃PO₄ loading and anhydrous proton conductivity are 92.2 wt % and 0.083 S cm^?1 at 165 °C, respectively. The high H₃PO₄ loading, reasonable proton conductivity in combination with simple preparation, low cost, and scalable matrix demonstrates the potential use of PAAm-g-CS hydrogel membranes in high-temperature proton exchange membrane fuel cells.     

High‐Temperature CO2 Electrolysis in Solid Oxide Electrolysis Cells: Developments,Challenges, and Prospects

High‐temperature CO₂ electrolysis in solid‐oxide electrolysis cells (SOECs) could greatly assist in the reduction of CO₂ emissions by electrochemically converting CO₂ to valuable fuels through effective electrothermal activation of the stable C?O bond. If powered by renewable energy resources, it could also provide an advanced energy‐storage method for their intermittent output. Compared to low‐temperature electrochemical CO₂ reduction, CO₂ electrolysis in SOECs at high temperature exhibits higher current density and energy efficiency and has thus attracted much recent attention. The history of its development and its fundamental mechanisms, cathode materials, oxygen‐ion‐conducting electrolyte materials, and anode materials are highlighted. Electrode, electrolyte, and electrode–electrolyte interface degradation issues are comprehensively summarized. Fuel‐assisted SOECs with low‐cost fuels applied to the anode to decrease the overpotential and electricity consumption are introduced. Furthermore, the challenges and prospects for future research into high‐temperature CO₂ electrolysis in SOECs are included.     

Study on the chemical stability of Y-doped BaCeO3 − δ and BaZrO3 − δ films deposited by aerosol deposition

Barium cerate (BaCeO₃) has high proton conductivity but rather poor chemical stability in CO₂-containing atmospheres. Barium zirconate (BaZrO₃), in contrast, is a rather stable material, but exhibits poor sinterability. In the present work, powders of Y-doped BaCeO₃ and BaZrO₃ were synthesized via the solid solution reaction method, and dense ceramic membranes with BaCe_0.9Y_0.1O₃ and BaZr_0.85Y_0.15O₃ were prepared by the aerosol deposition method at room temperature. Aerosol deposition method is a technique that enables the fabrication of ceramic films at room temperature with a high deposition rate as well as strong adhesion to the substrate. The powders and aerosol-deposited membranes were characterized by X-ray diffraction, particle size analysis, scanning electron microscopy, and X-ray elemental mapping. The chemical stability of powders and aerosol-deposited membranes with BaCe_0.9Y_0.1O₃ and BaZr_0.85Y_0.15O₃ against water and carbon dioxide has been investigated, and it was found that BaZr_0.85Y_0.15O₃ materials showed a better chemical compatibility.     

Synthesis of MoS2 and MoO2 for their applications in H2 generation and lithium ion batteries: a review

Abstract

Scientists increasingly witness the applications of MoS₂ and MoO₂ in the field of energy conversion and energy storage. On the one hand, MoS₂ and MoO₂ have been widely utilized as promising catalysts for electrocatalytic or photocatalytic hydrogen evolution in aqueous solution. On the other hand, MoS₂ and MoO₂ have also been verified as efficient electrode material for lithium ion batteries. In this review, the synthesis, structure and properties of MoS₂ and MoO₂ are briefly summarized according to their applications for H₂ generation and lithium ion batteries. Firstly, we overview the recent advancements in the morphology control of MoS₂ and MoO₂ and their applications as electrocatalysts for hydrogen evolution reactions. Secondly, we focus on the photo-induced water splitting for H₂ generation, in which MoS₂ acts as an important co-catalyst when combined with other semiconductor catalysts. The newly reported research results of the significant functions of MoS₂ nanocomposites in photo-induced water splitting are presented. Thirdly, we introduce the advantages of MoS₂ and MoO₂ for their enhanced cyclic performance and high capacity as electrode materials of lithium ion batteries. Recent key achievements in MoS₂- and MoO₂-based lithium ion batteries are highlighted. Finally, we discuss the future scope and the important challenges emerging from these fascinating materials.     

Novel preparation of expanded nano-graphene-based electrodes for EDLC and their improved electrochemical performance

The electrode raw materials in this work were composed of expanded nano-graphene (ENG)-based active carbon (YP50F) named YEG as an active material; Super-P carbon black (SPB) as an electric conductor; and styrene–butadiene rubber (SBR), sodium salt of carboxymethyl cellulose (CMC), and polytetrafluoroethylene ((C₂F₄)n, PTFE) as mixed binder materials. We characterized the prepared electrodes by X-ray diffraction, scanning electron microscopy, and Raman spectroscopic techniques. Finally, we examined the electrochemical performances of carbon materials in an electrolyte solution of tetraethylammonium tetrafluoroborate ((C₂H₅)₄NBF₄, TEABF4) in propylene carbonate (C₄H₆O₃, PC). The specific capacitance remains the same for smaller values of YEG in the composite electrodes. These results also provide evidence of the optimum loading of ENG in future graphene-based EDLCs.     

低介电常数微波介质陶瓷研究进展

随着微波通信技术向毫米波段延伸,低介电常数微波介质陶瓷的开发成为介质材料的研究热点。概述了Al2O3系、硅酸盐系、AAl2O4系(A=Zn、Mg)、钨酸盐系、磷酸盐系及石榴石结构化合物体系等低介电常数微波陶瓷材料体系的研究进展,并指出了低介电常数微波介质陶瓷目前存在的问题及发展趋势。     

Covalent Organic Frameworks: The Rising-Star Platforms for the Design of CO2 Separation Membranes

Membrane-based carbon dioxide (CO₂) capture and separation technologies have aroused great interest in industry and academia due to their great potential to combat current global warming, reduce energy consumption in chemical separation of raw materials, and achieve carbon neutrality. The emerging covalent organic frameworks (COFs) composed of organic linkers via reversible covalent bonds are a class of porous crystalline polymers with regular and extended structures. The inherent structure and customizable organic linkers give COFs high and permanent porosity, short transport channel, tunable functionality, and excellent stability, thereby enabling them rising-star alternatives for developing advanced CO₂ separation membranes. Therefore, the promising research areas ranging from development of COF membranes to their separation applications have emerged. Herein, this review first introduces the main advantages of COFs as the state-of-the-art membranes in CO₂ separation, including tunable pore size, modifiable surfaces property, adjustable surface charge, excellent stability. Then, the preparation approaches of COF-based membranes are systematically summarized, including in situ growth, layer-by-layer stacking, blending, and interface engineering. Subsequently, the key advances of COF-based membranes in separating various CO₂ mixed gases, such as CO₂/CH₄, CO₂/H₂, CO₂/N₂, and CO₂/He, are comprehensively discussed. Finally, the current issues and further research expectations in this field are proposed.     

Porous Materials Applied in Nonaqueous Li–O2 Batteries: Status and Perspectives

Porous materials possessing high surface area, large pore volume, tunable pore structure, superior tailorability, and dimensional effect have been widely applied as components of lithium–oxygen (Li–O₂) batteries. Herein, the theoretical foundation of the porous materials applied in Li–O₂ batteries is provided, based on the present understanding of the battery mechanism and the challenges and advantageous qualities of porous materials. Furthermore, recent progress in porous materials applied as the cathode, anode, separator, and electrolyte in Li–O₂ batteries is summarized, together with corresponding approaches to address the critical issues that remain at present. Particular emphasis is placed on the importance of the correlation between the function-orientated design of porous materials and key challenges of Li–O₂ batteries in accelerating oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) kinetics, improving the electrode stability, controlling lithium deposition, suppressing the shuttle effect of the dissolved redox mediators, and alleviating electrolyte decomposition. Finally, the rational design and innovative directions of porous materials are provided for their development and application in Li–O₂ battery systems.     

Effect of C6H14N2O7 and reaction temperature on sensing properties of hierarchical WO3 for H2S sensor

In this study, WO₃ nanoparticles with hierarchical structures are prepared by a simple hydrothermal method using diammonium hydrogen citrate (C₆H₁₄N₂O₇) as an additive, and the effects of reaction temperature and addition of C₆H₁₄N₂O₇ on their morphology are investigated in detail. The physical properties and morphology of the prepared WO₃ materials are analyzed by scanning electron microscopy, X-ray diffraction , transmission electron microscopy, and Brunauer–Emmett–Teller method, and a possible growth mechanism is proposed. The results show that C₆H₁₄N₂O₇ is adsorbed on the edges of the nanosheets and inhibits their anisotropic growth. In addition, based on this material, sensors are self-assembled for detecting the decomposition products of SF₆, and the gas-sensitive properties of the material are investigated. The experimental results show that the sensors based on WO₃ with hierarchical structures are highly sensitive to H₂S and exhibit a low operating temperature. This indicates that such sensors can be effectively used to detect the main decomposition products of SF₆.

     

C/C复合材料ZrB2基超高温陶瓷涂层的研究进展

ZrB₂基超高温陶瓷因其优异的高温抗氧化和烧蚀等性能,成为C/C复合材料理想的热防护涂层材料。本文从以下几个方面对C/C复合材料表面用ZrB₂基超高温陶瓷涂层的研究现状进行了综述:介绍了ZrB₂基超高温陶瓷涂层体系的主要制备技术,并对比了其制备的涂层抗氧化性和抗烧蚀性,总结了各制备方法的优点与不足;从单元、双元、三元材料掺杂改性的角度,详述了ZrB₂基复合涂层常见的材料体系,总结了其改性思路;介绍了ZrB₂基涂层在多层结构设计与开发方面的研究现状。最后简要展望了ZrB₂基超高温陶瓷涂层未来的研究方向。