SPES-C/MIL-53(Al)-SO3H杂化质子交换膜的制备和性能

用水热合成法制备MIL-53(Al),然后用后磺化法在其笼状结构中引入磺酸基团得到MIL-53(Al)-SO₃H纳米级金属有机框架(MOF)多孔晶体材料,最后将MIL-53(Al)-SO₃H掺杂到磺化酚酞侧基聚芳醚砜(SPES-C)高分子相中制备出一系列SPES-C/MIL-53(Al)-SO₃H燃料电池用杂化质子交换膜(PEM)。扫描电镜观测结果表明,杂化质子交换膜内没有缺陷,MIL-53(Al)-SO₃H在膜内分散均匀且两相的相容性好。热重分析结果证实,杂化膜具有优良的热稳定性。MIL-53(Al)-SO₃H的加入,提高了杂化膜的吸水率、尺寸稳定性和质子传导率。在温度为80℃时填充量为5%（质量分数）的杂化膜其M-5的质子传导率达到0.15 S·cm^-1,比纯SPES-C膜提高了32.5%且优于商用Nafion膜的质子传导率(0.134 S·cm^-1)。     

Carbonized Polymer Dots Assemble in Proton-Conducting Channels to Enhance the Conductivity and Selectivity Simultaneously for High-Performance Fuel Cells

Fabricating polymer electrolyte membranes (PEMs) simultaneously with high ion conductivity and selectivity has always been an ultimate goal in many membrane-integrated systems for energy conversion and storage. Constructing broader ion-conducting channels usually enables high-efficient ion conductivity while often bringing increased crossover of other ions or molecules simultaneously, resulting in decreased selectivity. Here, the ultra-small carbon dots (CDs) with the selective barriers are self-assembled within proton-conducting channels of PEMs through electrostatic interaction to enhance the proton conductivity and selectivity simultaneously. The functional CDs regulate the nanophase separation of PEMs and optimize the hydration proton network enabling higher-efficient proton transport. Meanwhile, the CDs within proton-conducting channels prevent fuel from permeating selectively due to their repelling and spatial hindrance against fuel molecules, resulting in highly enhanced selectivity. Benefiting from the improved conductivity and selectivity, the open-circuit voltage and maximum power density of the direct methanol fuel cell (DMFC) equipped with the hybrid membranes raised by 23% and 93%, respectively. This work brings new insight to optimize polymer membranes for efficient and selective transport of ions or small molecules, solving the trade-off of conductivity and selectivity.     

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.     

Constructing N?Cu?S Interface Chemical Bonds over SnS2 for Efficient Solar-Driven Photoelectrochemical Water Splitting

The restricted charge transfer and slow oxygen evolution reaction (OER) dynamics tremendously hamper the realistic implementation of SnS₂ photoanodes for photoelectrochemical (PEC) water splitting. Here, a novel strategy is developed to construct interfacial N Cu S bonds between N C skeletons and SnS₂ (Cu N C@SnS₂) for efficient PEC water splitting. Compared with SnS₂, the PEC activity of Cu N C@SnS₂ photoelectrode is tremendously heightened, obtaining a current density of 3.40 mA cm² at 1.23 V_RHE with a negatively shifted onset potential of 0.04 V_RHE, which is 6.54 times higher than that of SnS₂. The detailed experimental characterizations and theoretical calculation demonstrate that the interfacial N Cu S bonds enhance the OER kinetic, reduce the surface overpotential, facilitate the separation of photon-generated carriers, and provide a fast transmission channel for electrons. This work presents a new approach for modulating charge transfer by interfacial bond design in heterojunction photoelectrodes toward promoting PEC performance and solar energy application.     

Preparation of PV dF-based electrospun membranes and their application as separators

A one-step method preparing of poly(vinylidene fluoride)-based electrospun membranes (PEMs) containing TiO₂ has been developed. The effect of TiO₂ on the morphology, degree of crystallization and electrochemical behavior of PEMs was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and electrochemical measurements. The PEMs containing TiO₂ show improved ionic conductivity and cycling performance compared with pure PEMs.     

Preparation of PVdF-based electrospun membranes and their application as separators

Abstract

A one-step method preparing of poly(vinylidene fluoride)-based electrospun membranes (PEMs) containing TiO₂ has been developed. The effect of TiO₂ on the morphology, degree of crystallization and electrochemical behavior of PEMs was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and electrochemical measurements. The PEMs containing TiO₂ show improved ionic conductivity and cycling performance compared with pure PEMs.     

Self‐Healing Proton‐Exchange Membranes Composed of Nafion–Poly(vinyl alcohol) Complexes for Durable Direct Methanol Fuel Cells

Proton‐exchange membranes (PEMs) that can heal mechanical damage to restore original functions are important for the fabrication of durable and reliable direct methanol fuel cells (DMFCs). The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen‐bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4‐carboxybenzaldehyde (CBA) molecules is presented. Compared with pure Nafion, the CBA/Nafion–PVA membranes exhibit enhanced mechanical properties with an ultimate tensile strength of ≈20.3 MPa and strain of ≈380%. The CBA/Nafion–PVA membrane shows a proton conductivity of 0.11 S cm^?1 at 80 °C, which is 1.2‐fold higher than that of a Nafion membrane. The incorporated PVA gives the CBA/Nafion–PVA membranes excellent proton conductivity and methanol resistance. The resulting CBA/Nafion–PVA membranes are capable of healing mechanical damage of several tens of micrometers in size and restoring their original proton conductivity and methanol resistance under the working conditions of DMFCs. The healing property originates from the reversibility of hydrogen‐bonding interactions between Nafion and CBA‐modified PVA and the high chain mobility of Nafion and CBA‐modified PVA.     

Nanoclay-Modulated Interfacial Chemical Bond and Internal Electric Field at the Co3O4/TiO2 p-n Junction for Efficient Charge Separation

To achieve a high separation efficiency of photogenerated carriers in semiconductors, constructing high-quality heterogeneous interfaces as charge flow highways is critical and challenging. This study successfully demonstrates an interfacial chemical bond and internal electric field (IEF) simultaneously modulated 0D/0D/1D-Co₃O₄/TiO₂/sepiolite composite catalyst by exploiting sepiolite surface-interfacial interactions to adjust the Co²⁺/Co³⁺ ratio at the Co₃O₄/TiO₂ heterointerface. In situ irradiation X-ray photoelectron spectroscopy and density functional theory (DFT) calculations reveal that the interfacial Co²⁺ O Ti bond (compared to the Co³⁺ O Ti bond) plays a major role as an atomic-level charge transport channel at the p-n junction. Co²⁺/Co³⁺ ratio increase also enhances the IEF intensity. Therefore, the enhanced IEF cooperates with the interfacial Co²⁺ O Ti bond to enhance the photoelectron separation and migration efficiency. A coupled photocatalysis-peroxymonosulfate activation system is used to evaluate the catalytic activity of Co₃O₄/TiO₂/sepiolite. Furthermore, this work demonstrates how efficiently separated photoelectrons facilitate the synergy between photocatalysis and peroxymonosulfate activation to achieve deep pollutant degradation and reduce its ecotoxicity. This study presents a new strategy for constructing high-quality heterogeneous interfaces by consciously modulating interfacial chemical bonds and IEF, and the strategy is expected to extend to this class of spinel-structured semiconductors.     

Synthesis and properties of sulfonated polyimide–polybenzimidazole copolymers as proton exchange membranes

Chemical stability of polymer electrolyte membranes (PEMs) is the key factor affecting the lifetime of fuel cells. It is greatly desirable to develop the PEMs with both high proton conductivity and excellent chemical stability. In this study, a series of sulfonated polyimide–polybenzimidazole copolymers (SPI-co-PBIs) are synthesized via random condensation polymerization of 1,4,5,8-naphthalene tetracarboxylic dianhydride, 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid, and an amine-terminated polybenzimidazole oligomer. The ion exchange capacities of the resulting SPI-co-PBIs are in the range 1.90–2.47 meq g^?1. Under fully hydrated condition, the SPI-co-PBI membranes show higher proton conductivities than Nafion112. It is found that the incorporation of a small fraction of PBI moiety into the polyimide structure resulted in significant improvement in radical oxidative stability. For example, the SPI-co-PBI-19/1 containing 5 mol % PBI moiety shows only 0.6 wt% weight loss after being soaked in the Fenton’s reagent (3 % H₂O₂ + 3 ppm FeSO₄) at 80 °C for 150 min, whereas the corresponding benzimidazole group-free sulfonated polyimide is completely dissolved in the Fenton’s reagent at 80 °C for 140 min. The SPI-co-PBI membranes also show excellent hydrolytic stability due to the highly stable ladder structure of the benzimidazobenzisoquinolinone linkages.     

Proton conducting membranes composed of hydronium alunite

High proton conductivity, of 3 × 10^?4 ohm^?1 cm^?1 at 20°C, has been found in hydrated pressed discs of hydronium alunite, of formula (H₃O)Al₃(SO₄)₂(OH)₆. The conduction occurs within the hydrated interparticle regions into which protons have been donated, probably from the H₃O⁺ groups exposed on the crystal surfaces. The general utility of the membranes is discussed.     

Proton conduction in solids—A Raman spectral study

The mechanism of proton conduction in hydrogen-bonded solids and the importance of Raman investigations to understand it are discussed here. The results of Raman investigations on the protonic conductors (NH₄)₃H(SO₄)₂ and Li₂SO₄·H₂O under small d.c. electric fields have been discussed. The enhancement in intensity of the 859, 829 and 330 cm^?1 bands of(NH₄)₃H(SO₄)₂ has been explained on the basis of proton movement along the N-H...O bond. Spectral changes of the bands due to torsional oscillation of the ammonium ion indicate the probability of hindered rotation of this group. The appearance of new bands at 773 and 1680cm^?1 in Li₂SO₄·H₂O indicates the formation of H₃O⁺ electrolysis. The changes in stretching and bending modes of water are explained on the basis of polarizability changes induced by the migration of proton along the 0-H...0 bond and reorientation motion of water molecules.     

Super Proton Conductivity Through Control of Hydrogen-Bonding Networks in Flexible Metal–Organic Frameworks

Metal–organic frameworks (MOFs) have received much attention as a solid-state electrolyte in proton exchange membrane fuel cells. The introduction of proton carriers and functional groups into MOFs can improve the proton conductivity attributed to the formation of hydrogen-bonding networks, while the underlying synergistic mechanism is still unclear. Here, a series of flexible MOFs (MIL-88B, [Fe₃O(OH)(H₂O)₂(O₂C-C₆H₄-CO₂)₃] with imidazole) is designed to modify the hydrogen-bonding networks and investigate the resulting proton-conducting characteristics by controlling the breathing behaviors. The breathing behavior is tuned by varying the amount of adsorbed imidazole into pore (small breathing (SB) and large breathing (LB)) and introducing functional groups onto ligands (-NH₂, -SO₃H), resulting in four kinds of imidazole-loaded MOFs−Im@MIL-88B-SB, Im@MIL-88B-LB, Im@MIL-88B-NH₂, and Im@MIL-88B-SO₃H. Im@MIL-88B-LB without functional groups exhibits the highest proton conductivity of 8.93 × 10⁻² S cm⁻¹ at 60 °C and 95% relative humidity among imidazole-loaded proton conductors despite the mild condition, indicating that functional groups may not be always required to enhance proton conductivity. The elaborately controlled pore size and host–guest interaction in flexible MOFs through imidazole-dependent structural transformation are translated into the high proton concentration without the limitation of proton mobility, contributing to the formation of effective hydrogen-bonding networks in imidazole conducting media.     

Preparation of new proton exchange membranes using sulfonated poly(ether sulfone) modified by octylamine (SPESOS)

Sulfonated poly(arylene ether sulfone) (SPES) has received considerable attention in membrane preparation for proton exchange membrane fuel cell (PEMFC). But such membranes are brittle and difficult to handle in operation. We investigated new membranes using SPES grafted with various degrees of octylamine. Five new materials made from sulfonated polyethersulfone sulfonamide (SPESOS) were synthetized with different grades of grafting. They were made from SPES, with initially an ionic exchange capacity (IEC) of 2.4 meq g⁻¹ (1.3 H⁺ per monomer unit). Pristine SPES with that IEC is water swelling and becomes soluble at 80 °C, its proton conductivity is in the range of 0.1 S cm⁻¹ at room temperature in aqueous H₂SO₄ 1 M, similar to that of Nafion^®. After grafting with various amounts of octylamine, the material is water insoluble; membranes are less brittle and show sufficient ionic conductivity. Proton transport numbers were measured close to 1.     

First principles study of isotope effect in hydrogen-bonded K3H(SO4):: II — Zero-point oscillation effect

First principles calculation is performed to find the difference between K₃H(SO₄)₂ (KHS) and K₃D(SO₄)₂ (DKHS) by taking account of the zero-point oscillation effects of the proton and the deuteron. First, we calculate the potential surface for the proton in the crystal. The ground-state energies and the wavefunctions of the proton and the deuteron in that potential are calculated. Then, the stable positions of the proton and the deuteron are calculated taking account of zero-point energy, and the electric charge distributions are calculated taking account of the spread wavefunctions of the proton and the deuteron. As a result, we find that the anharmonicity of the proton potential surface makes the position of the hydrogen closer to the center of the hydrogen bond than that of the deuterium. We also find that the zero-point oscillation effect diminishes the dipole moments, and that the shrinkage of the dipole moment in the hydrogen system is larger than that of the deuteron. These two effects play significant roles in the mechanism of the isotope effect in KHS.     

Proton conductivity of zirconium tricarboxybutylphosphonate/PBI nanocomposite membrane

The preparation process and proton transport properties of zirconium tricarboxybutylphosphonate Zr(O₃PC(CH₂)₃(COOH)₃)₂ (Zr(PBTC))/polybenzimidazole (PBI) composite membranes have been investigated with a view to developing a novel electrolyte for direct methanol fuel cells. A compacted Zr(PBTC) powder sample and a Zr(PBTC)/PBI composite membrane with 50 wt.% Zr(PBTC) content show conductivities of 6.74 × 10^–2 S cm^–1 and 3.82 × 10^–3 S cm^–1 at 200 °C under a fully humid condition, respectively. Post-sulfonation thermal treatment, which has a great effect on the ligand structure of PBI, gives a marked increase in the conductivity of the membrane by a factor of 2 in the same condition. This effect is mainly attributed to the proton transport via sulfonic acid groups bonded to the PBI unit.     

Properties and in vitro biological evaluation of nano-hydroxyapatite/chitosan membranes for bone guided regeneration

Nano-hydroxyapatite(n-HA)/chitosan(CS) composite membranes were prepared by solvent casting and evaporation methods for the function of guided bone regeneration (GBR). The effect of n-HA content and solvent evaporation temperature on the properties of the composite membranes was studied. The n-HA/CS membranes were analyzed by scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray diffraction, swelling measurement, mechanical test, cell culture and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenylte-2H-tetrazolium bromide) assay. The results show that the surface roughness and micropores of the composite membranes increase with the rise of n-HA content, suitable for adhesion, crawl and growth of cells. The hydroxyapatite holds nano size and distributes uniformly in the composite membranes. Chemical bond interaction exists between Ca ions and –OH groups of n-HA and –NH₂ or –OH groups of CS. The n-HA content and solvent evaporation temperature have obvious influence on the swelling ratio, tensile strength and elongation rate of the composite membranes. Cell culture and MTT assays show that n-HA and its content can affect the proliferation of cells. The n-HA/CS composite membranes have no negative effect on the cell morphology, viability and proliferation and possess good biocompatibility. This study makes the n-HA/CS composite membrane be a prospective biodegradable GBR membrane for future applications.     

Atomic Interface Engineering of Single-Atom Pt/TiO2-Ti3C2 for Boosting Photocatalytic CO2 Reduction

Solar-driven CO₂ conversion into valuable fuels is a promising strategy to alleviate the energy and environmental issues. However, inefficient charge separation and transfer greatly limits the photocatalytic CO₂ reduction efficiency. Herein, single-atom Pt anchored on 3D hierarchical TiO₂-Ti₃C₂ with atomic-scale interface engineering is successfully synthesized through an in situ transformation and photoreduction method. The in situ growth of TiO₂ on Ti₃C₂ nanosheets can not only provide interfacial driving force for the charge transport, but also create an atomic-level charge transfer channel for directional electron migration. Moreover, the single-atom Pt anchored on TiO₂ or Ti₃C₂ can effectively capture the photogenerated electrons through the atomic interfacial Pt O bond with shortened charge migration distance, and simultaneously serve as active sites for CO₂ adsorption and activation. Benefiting from the synergistic effect of the atomic interface engineering of single-atom Pt and interfacial Ti O Ti, the optimized photocatalyst exhibits excellent CO₂-to-CO conversion activity of 20.5 µmol g⁻¹ h⁻¹ with a selectivity of 96%, which is five times that of commercial TiO₂ (P25). This work sheds new light on designing ideal atomic-scale interface and single-atom catalysts for efficient solar fuel conversation.     

Effects of ion beam surface modification on water absorption characteristics of perfluorosulfonic acid membranes

The dynamic behavior of water within ion beam (10 keV Ar⁺, 1.0 × 10¹⁶–1.2 × 10¹⁷ ions/cm²) modified perfluorosulfonic acid (PFSA) membranes was investigated at room temperature by combining direct-current (DC) resistance with alternative-current (AC) impedance methods under a water-saturated air atmosphere. The bulk impedance in existing surface sulfonate groups (SO₃⁻) decreased approximately one order of magnitude as a result of Ar⁺ ion irradiation compared to the unirradiated membrane. The enhancement in the proton conductivity results in an improvement of the water absorption characteristics at the Ar⁺ ion-modified surface which showed large superficies as well as hydrophilic radicals. These results can be explained in base of a relative increase in both the water content of the membrane and the change in the interactions of water molecules with sulfonate group at the interface on the proton-transfer process.     

Research on hydrophobicity of electrospun Fe3O4/PVDF nanofiber membranes under different preparation conditions

Abstract

Preparation condition can affect the structure and the properties of nanofiber membrane. In order to explore suitable conditions to prepare the Fe₃O₄/PVDF nanofiber membrane with good hydrophobicity, the hydrophobicity of Fe₃O₄/PVDF nanofiber membranes obtained by electrospinning was investigated by changing preparation conditions like weight percentage of Fe₃O₄ nanoparticles, blending quality concentration of poly (vinylidene fluoride) (PVDF) and Fe₃O₄ nanoparticles, and positive voltage. And the variations of hydrophobicity of Fe₃O₄/PVDF nanofiber membranes modified by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane were studied. The results show that the hydrophobicity of Fe₃O₄/PVDF nanofiber membranes has changed under different preparation conditions. The contact angles of samples increased after a modification by 1H, 1H, 2H, 2H-perfluorodecyl trimethoxysilane, which indicates that the hydrophobicity of Fe₃O₄/PVDF nanofiber membranes has been enhanced.     

A review of advanced proton-conducting materials for hydrogen separation

This paper provides a comprehensive overview of developments and recent trends in H₂ separation technology that uses dense proton–electron conducting ceramic materials and their associated membranes. Various proton–electron conducting materials and their associated membranes are summarized and classified into several important categories, such as Ni-composite proton-conducting materials, as well as tungstate-based, BaPrO₃-based, LaGaO₃-based, and niobate/tantalite composite metal oxide-based ceramic materials/membranes. Various membrane designs, including asymmetric ceramic membranes (supported and self-supported) and surface-modified membranes, are also reviewed. Several important properties of ceramic materials and membranes, such as proton and electron conductivity and performance (i.e., H₂ transport flux and lifetime stability), are also discussed. To highlight the technical progress in this area, all possible ceramic materials and associated membranes are summarized, along with their properties and performance, to help readers quickly locate the information they are looking for. Based on this review, several challenges hindering the maturation of this technology are analyzed in depth, and possible research directions for overcoming these challenges are suggested.