Excellent Proton Conductivity Research Articles

Preparation and study on H–MoS2/SLS modified SPI@SPEEK blend proton exchange membrane with balanced proton conductivity and stability

Proton exchange membranes (PEMs) are the core components of fuel cells, and research has long focused on how to balance their proton conductivity and durability. In this work, a series of homogeneous blend of sulfonated polyimide (SPI) and sulfonated polyether ether ketone (SPEEK) hybrid membranes with were constructed refined with sulfonated MoS2 (H–MoS2) and sodium lignosulfonate (SLS). The results showed that the tensile strength of the films was enhanced by 39.4% (67.84 MPa) compared to the base film. The composite films incorporating 1 wt% H-MoS2 and 2 wt% SLS has excellent proton conductivity, which can reach 50.24 mS/cm at 80°C and 100% humidity. The embed hybrid structure constructed by H–MoS2 and SLS, which not only effectively solves the limitations of the proton transport channel of traditional polymer materials, but also provides abundant proton transport sites, which provides a new strategy for preparing high-performance PEM.

The effect of nitrogen positive sites on the proton conductivity and acid stability of polybenzimidazole-based proton exchange membranes

High-temperature proton exchange membranes (HT-PEMs) based on amino-type polybenzimidazole (AmPBI) and double-bonded ionic liquids (ILs) are prepared. To prevent leakage of ILs, three kinds of polymeric ionic liquids (PILs) with different nitrogen positive sites are synthesized through in-situ free radical polymerization, and then the AmPBI-PIL membranes are prepared. The ion pairs (N+ - H2PO4−) formed after treatment with KOH and PA have a good effect on both proton conductivity and PA retention. After acid doping, the nitrogen positive sites in the PILs form ion pairs with PA, which serves as a jumping site for protons and promotes proton transport. The excellent proton conductivity and PA remaining of the AmPBI-PIL membranes are noteworthy. In particular, the proton conductivity of AmPBI-CTDTr is as high as 184.9 mS cm−1 at 180 °C, and the acid reservation is 83 % at 160 °C after 240 h. AmPBI-CTDTr has a 550.9 mW cm−2 peak power density when it is anhydrous at 160 °C.

Double cross-linked 3D layered PBI proton exchange membranes for stable fuel cell performance above 200 °C

Phosphoric acid doped proton exchange membranes often experience performance degradation above 200 °C due to membrane creeping and phosphoric acid evaporation, migration, dehydration, and condensation. To address these issues, here we present gel-state polybenzimidazole membranes with double cross-linked three-dimensional layered structures via a polyphosphoric acid sol-gel process, enabling stable operation above 200 °C. These membranes, featuring proton-conducting cross-linking phosphate bridges and branched polybenzimidazole networks, effectively anchor and retain phosphoric acid molecules, prevent 96% of its dehydration and condensation, improve creep resistance, and maintain excellent proton conductivity stability. The resulting membrane, with superior through-plane proton conductivity of 0.348 S cm−1, delivers outstanding peak power densities ranging from 1.20–1.48 W cm−2 in fuel cells operated at 200-240 °C and a low voltage decay rate of only 0.27 mV h−1 over a 250-hour period at 220 °C, opening up possibilities for their direct integration with methanol steam reforming systems.

Hybrid Membrane of Sulfonated Poly(aryl ether ketone sulfone) Modified by Molybdenum Clusters with Enhanced Proton Conductivity.

Developing novel proton exchange membranes (PEMs) with low cost and superior performance to replace Nafion is of great significance. Polyoxometalate-doped sulfonated poly(aryl ether ketone sulfone) (SPAEKS) allows for the amalgamation of the advantages in each constituent, thereby achieving an optimized performance for the hybrid PEMs. Herein, the hybrid membranes by introducing 2MeIm-{Mo132} into SPAEKS are obtained. Excellent hydrophilic properties of 2MeIm-{Mo132} can help more water molecules be retained in the hybrid membrane, providing abundant carriers for proton transport and proton hopping sites to build successive hydrophilic channels, thus lowering the energy barrier, accelerating the proton migration, and significantly fostering the proton conductivity of hybrid membranes. Especially, SP-2MIMo132-5 exhibits an enhanced proton conductivity of 75mScm-1 at 80°C, which is 82.9% higher than pristine SPAEKS membrane. Additionally, this membrane is suitable for application in proton exchange membrane fuel cells, and a maximum power density of 266.2mWcm-2 can be achieved at 80°C, which far exceeds that of pristine SPAEKS membrane (54.6mWcm-2). This work demonstrates that polyoxometalate-based clusters can serve as excellent proton conduction sites, opening up the choice of proton conduction carriers in hybrid membrane design and providing a novel idea to manufacture high-performance PEMs.

High ion exchange capacity perfluorosulfonic acid resine proton exchange membrane for high temperature applications in polymer electrolyte fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have attract much attention from academic and industry, which can improve the catalyst activity, reduce Pt loading, enhance CO tolerance, and simplify water and heat management. High-temperature proton exchange membrane (HT-PEM) is the key component for HT-PEMFCs. Here, we provide an investigation of newly developed HT-PEM to evaluate its properties and performances in fuel cells above 90 °C. The HT-PEM exhibits an excellent proton conductivity of 136.1 mS cm−1 at 90 °C and 95% RH, and remarkable power density of 0.95 Wcm−2 at 105 °C and 80% RH. The stability and durability of HT-PEM are studied with varied testing methods. After the continuous operation at open circuit voltage (OCV) for 500 h and continuous dry-wet circulation for 20000 cycles at 90 °C, negligible change of OCV and hydrogen permeation current density are recorded, indicating good chemical and mechanical stability for HT-PEM. The improved property and performance originate from the new PFSA base material and improved morphology, in which the larger ionic clusters and continuous proton-transfer channels contribute to the superior performance, and the high glass transition temperature (Tg∼132 °C) induces good stability.

A multifunctional Eu-MOF with multi-color and proton conduction switching and its anti-counterfeiting applications

Lanthanide metal-organic frameworks (Ln-MOFs) have exhibited remarkable capabilities in color change, luminescence, proton conduction through the strategic modification of metal nodes, organic ligands and channels or pores. By modifying the electron-deficient bipyridinium to contain carboxylic acid moieties and coordinating them with the luninescent Eu3+ ion, a unique and versatile Eu-MOF has been synthesized. Under UV light conditions, the complex shows an obvious color change from colorless to blue, which is due to the formation of viologen radicals after photoinduced electron transfer (PIET) process. As we all know, the changed color is caused by the alteration of absorption intensity, ultimately impacting its luminescence as well. Thus, the bright and strong red fluorescence of this complex is quenched upon continuous UV light irradiation, which may be attributed to intramolecular energy transfer from the excited state of the europium ion to the colored state of the CV ligand. Based on the control of multiple colors of the complex, the designed encryption model can realize multiple anti-counterfeiting of real numbers. In addition, the conductivity of this compound increases significantly after UV illumination, showing excellent photo-modulated proton conductivity. In short, our work has proposed a multifunctional bipyridinium-based Ln-MOF with photochromism, photo-switchable photoluminescence and proton conduction, which offers valuable insights for the creation of versatile switchable materials based on MOFs.

Improving the proton conductivity of HKUST‐1 by hole expansion and ionic liquid introduction

As a new type of proton conductor, metal–organic frameworks (MOFs) have attracted much attention because of their superior properties over conventional materials, such as the modifiability of framework, reversibility of coordination bond, high specific surface area, and porosity. It is predicted that the proton conductivities of MOFs can be improved by hole expansion and ionic liquid introduction. In this work, HKUST‐1 and LP‐HKUST‐1 were prepared, which were filled with different proportions of N‐methylimidazole triflate (MIM‐CF3SO3) to prepare composite materials MIM‐CF3SO3@HKUST‐1‐100% and MIM‐CF3SO3@LP‐HKUST‐1‐x (x = 25%, 50%, 75% and 100%). A total of seven kinds of materials were synthesized. The proton conductivities of all the materials at 75% RH were tested from 303 to 353 K. In this environment, MIM‐CF3SO3@LP‐HKUST‐1‐100% shows excellent proton conductivity (σ = 0.341 S·cm−1 at 353 K, 75% relatively humidity [RH]), being 7060 times that of HKUST‐1, and reaches the peak value of MOF family in recent years. Then, the conductivities of parts of the materials were tested in extreme environments, such as in high‐humidity environment (303–353 K, 100% RH), high‐temperature environment (373–423 K, N2 atmosphere), and low‐temperature environment (253–283 K, 75% RH). The results show that under all conditions above, the proton conductivity of MIM‐CF3SO3@LP‐HKUST‐1‐100% is the best, up to 0.341 S·cm−1 at 353 K and 75% RH, 0.179 S·cm−1 at 353 K and 100% RH, 1.31 × 10−3 S·cm−1 at 283 K and 75% RH, and 2.31 × 10−4 S·cm−1 at 423 K and N2 atmosphere, indicating that proton conductivity of HKUST‐1 is improved by hole expansion and ionic liquid introduction. Finally, the stability test showed that MIM‐CF3SO3@LP‐HKUST‐1‐100% was stable in all environments above. Moreover, the conductive mechanism of HKUST‐1 before and after introduction of ionic liquids was also discussed, providing a theoretical basis for the enhancement of proton conductivities of MOFs using ionic liquid introduction and hole expansion.

Assessment of polybenzimidazole/MOF composite membranes for the improvement of high-temperature PEM fuel cell performance

This study aims to determine the most effective utilization of ZIF-8 type metal-organic framework (MOF) doped polybenzimidazole (PBI) composite membrane in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) and investigate how ZIF-8 filler affects performance. ZIF-8 particles were prepared by solvothermal method and added to the PBI polymer using a weight percentage varying from 1 to 5 %. XRD, BET, and TEM examined the prepared ZIF-8. Composite membrane properties were investigated by XRD, SEM analysis, proton conductivity measurements, acid doping, and acid stripping tests. The HT-PEMFC performances of the membranes were carried out using Hydrogen and dry air at 150–180. The highest performance was acquired with the composite ZIF8/PBI-2 membrane as 0.432 W/cm2 at 170 °C. The obtained result is explained by easier proton transfer over ZIF-8's enlarged tunnel network. This study proposes a promising strategy to use ZIF-8 to prepare a PBI composite membrane with excellent proton conductivity, acid doping, and low acid leaching for HT-PEMFC application. The current study's findings can support future research on PBI/MOF-based composite membranes for HT-PEMFC applications.

Hierarchical Self-Assembly of Capsule-Shaped Zirconium Coordination Cages with Quaternary Structure.

Biological macromolecules exhibit emergent functions through hierarchical self-assembly, a concept that is extended to design artificial supramolecular assemblies. Here, the first example of breaking the common parallel arrangement of capsule-shaped zirconium coordination cages is reported by constructing the hierarchical porous framework ZrR-1. ZrR-1 adopts a quaternary structure resembling protein and contains 12-connected chloride clusters, representing the highest connectivity for zirconium-based cages reported thus far. Compared to the parallel framework ZrR-2, ZrR-1 demonstrated enhanced stability in acidic aqueous solutions and a tenfold increase in BET surface area (879m2 g-1 ). ZrR-1 also exhibits excellent proton conductivity, reaching 1.31×10-2 S·cm-1 at 353K and 98% relative humidity, with a low activation energy of 0.143eV. This finding provides insights into controlling the hierarchical self-assembly of metal-organic cages to discover superstructures with emergent properties.

Dual-Proton Conductor for Fuel Cells with Flexible Operational Temperature.

The properties of proton conductors determine the operating temperature range of fuel cells. Typically, phosphoric acid (PA) proton conductors exhibit excellent proton conductivity owing to their high proton dissociation and self-diffusion abilities. However, at low temperatures or high current densities, water-induced PA loss causes rapid degradation of cell performance. Maintaining efficient and stable proton conductivity within a flexible temperature range can significantly reduce the start-up temperature of PA-doped proton exchange membrane fuel cells. In this study, a dual-proton conductor composed of an organic phosphonic acid (ethylenediamine tetramethylene phosphonic acid, EDTMPA) and an inorganic PA is developed for proton exchange membranes. The proposed dual-proton conductor can operate within a flexible temperature range of 80-160 °C, benefiting from the strong interaction between EDTMPA and PA, and the enhanced proton dissociation. Fuel cells with the EDTMPA-PA dual-proton conductor showed excellent cell stability at 80 °C. In particular, under the high current density of 1.5 A cm-2 at 160 °C, the voltage decay rate of the fuel cell with the dual-proton conductor is one-thousandth of that of the fuel cell with PA-only proton conductor, indicating excellent stability.

Proton exchange membrane deriving from sulfonated N-heterocyclic poly(aryl ether ketone)s containing ether-free proton conducting units and performing enhanced physicochemical stability and conduction properties

Sulfonated aromatic polymer proton exchange membranes suffer from the trade-off relationship between physicochemical stability and proton conductivity hampering the membrane application in fuel cells. To bridge the effect, the high-performance membranes exhibiting excellent proton conduction behavior and good stability are constructed from sulfonated N-heterocyclic poly(aryl ether)s designed elaborately, in which the hydrophilic units are constructed by combining the high-density pendant benzenesulfonic groups and biphthalazindione structures without the introduction of weak linkage units like ether bonds. The twisted heterocyclic structures and the multiple interactions between heterocyclic structures and sulfonic groups enhance the physical stability and proton-conduction behavior with the highest conductivity of 256 mS cm−1 for the membranes. The membranes perform rupture time between 3.9 and 7.1 h in high temperature Fenton's oxidation test, exhibiting good chemical stability. The cells loading the membranes perform the maximum power density between 1.08 and 2.30 W cm−2. The above results verify the benefits of constructing ether-free heterocyclic hydrophilic units with high-density proton-conducting groups for the improvement of comprehensive membrane performance.

Nanocellulose as a Sustainable Polymer Electrolyte

Polymer electrolyte membranes in fuel cells and electrolyzers will play a key role in the hydrogen economy. These membranes are generally made of sulfonated fluoropolymers, which have excellent proton conductivity, impressive redox stability, and good gas barrier properties. However, the complex synthetic processes mean that they remain expensive. Their synthesis also involves ecologically damaging perfluorosulfonic acids (PFSAs), otherwise known as “forever chemicals” due to their persistence in the environment. More sustainable and lower cost hydrocarbon electrolytes should therefore be investigated.Cellulose is the most abundant biopolymer in nature, and is derived from plant matter. It is used at vast scale and low cost to make paper and cardboard. Cellulose can be chemically or mechanically treated to break up the fibers to form “nanocellulose”. Nanocellulose is a low-cost nanomaterial which can be formed into thin membranes which are much stronger than conventional cellulosic paper.We propose nanocellulose as an alternative electrolyte to replace sulfonated fluoropolymers in fuel cells. We confirmed that unmodified nanocellulose can conduct protons due to acidic hydroxyl groups. We also showed that nanocellulose membranes present a much better barrier to hydrogen compared to Nafion, and can successfully be used as an electrolyte in fuel cells. However, the current-voltage performance of unmodified nanocellulose was insufficient due to a high membrane resistance.We went on to improve the proton conductivity by introducing sulfonic acid groups and reduced the membrane resistance by using spray deposition to create thinner membranes, resulting in significantly improved fuel cell power density of 160 mW/cm2. We also implemented crosslinking with sulfosuccinic acid to simultaneously improve the ionic conductivity, increase strength, and reduce swelling in water. This work shows that nanocellulose is a promising new class of polymer electrolyte which could significantly reduce the cost and improve sustainability of fuel cell and electrolyser systems.1. Cellulose Nanocrystals Crosslinked with Sulfonic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications, O. Selyanchyn, T. Bayer, D. Klotz, R. Selyanchyn, K. Sasaki, S. M. Lyth, Membranes 12 (7), 658 (2022)2. Spray Deposition of Sulfonated Cellulose Nanofibers as Proton Conducting Membranes for Fuel Cells, T. Bayer, B. Cunning, R. Selyanchyn, B. Smid, S. Fujikawa, K. Sasaki, S. M. Lyth, Cellulose, 28, 1355–1367 (2021)3. Proton Conductivity in Cellulosic Materials: A Review, O. Selyanchyn, R. Selyanchyn, S. M. Lyth, Frontiers in Energy Research: Fuel Cells, 8, 596164 (2020)4. High Temperature Proton Conductivity in Nanocellulose: Paper Fuel Cells, T. Bayer, R. Selyanchyn, S. Fujikawa, K. Sasaki, and S. M. Lyth, Chemistry of Materials, 28 (13), 4805–4814 (2016)

(Invited) Understanding the Performance Limits of Solid Acid Fuel Cells with Pt Electrocatalysts

Solid acid fuel cells (SAFCs) confer unique functional benefits over nearby technologies due to the solid state nature and intermediate temperature operability of the electrolyte. Amongst candidate solid acids, the electrolyte of choice in fuel cell applications is almost exclusively cesium dihydrogen phosphate (CDP), CsH2PO4. The material displays excellent proton conductivity (~2 ∗ 10-2 S/cm) at moderate temperatures (228 – 300 °C) with no detectable electronic conductivity. The elevated temperature of operation relative to polymer electrolyte membrane (PEM) fuel cells (< 90 °C), suggests that the kinetics for the oxygen reduction reaction will be elevated, and that SAFCs should provide higher power densities at reduced catalyst loadings. In practice, however, these advantages have not been realized. State-of-the-art SAFCs produce peak power densities of ~200 mW/cm2 with Pt loadings of 1.75 mg/cm2.1 In comparison, PEMFCs have demonstrated peak power densities >1 W/cm2 with Pt loadings of only 0.1 mg/cm2.2 In this work, we begin to unravel the question of why the anticipated thermal activation of reaction kinetics has not resulted in superior SAFC performance. We measure fundamental microstructural and material parameters of SAFC cathodes, and use these to predict fuel cell polarization curves. We find that, while the exchange current density for the oxygen reduction reaction is high in SAFCs, the Tafel slope is steep. Thus, the fundamental steps in the ORR reaction on Pt follow a different and unfavorable pathway under SAFC conditions than PEMFC conditions.We further employ the experimentally informed and validated physical model (see figure) to assess the role of microstructural, operational, and material parameters on SAFC polarization curves. The model suggests that a 10-fold increase in active Pt surface area would be required to approach the DOE fuel cell target of 300 mA/cm2 at 0.8 V (even without accounting for voltage drops through the ~ 50 mm thick electrolyte). In turn, this would require a decrease in CDP particle size in the cathode, where CDP serves as the support onto which Pt nanoparticles are deposited, from 500 to 50 nm, and would be accompanied by an untenable increase in Pt loading to over 30 mg/cm2. We further find that the Pt catalytic activity is strongly inhibited by the presence of steam, required to maintain stability of the electrolyte against dehydration. The humidification requirement moreover increases polarization losses at higher temperatures of operation, at which higher steam levels are required for electrolyte stabilization, overcoming the expected benefits of thermally activated catalysis. These insights motivate prioritization of the development and deployment of alternative catalyst materials and advanced electrolytes with greater thermodynamic stability over attempts to modify electrode microstructure, cell architecture, or operational conditions using today’s material set in order to advance SAFC technology towards commercial realization.1. Papandrew, A. B., Chisholm, C. R. I., Elgammal, R. A., Özer, M. M. & Zecevic, S. K. Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH2PO4. Chemistry of Materials 23, 1659-1667, (2011).2. Zhao, Z. et al. Graphene-nanopocket-encaged PtCo nanocatalysts for highly durable fuel cell operation under demanding ultralow-Pt-loading conditions. Nat Nanotechnol, (2022). Figure 1

Self-Healing Sulfonated Poly(ether ether ketone)-Based Polymer Electrolyte Membrane for Direct Methanol Fuel Cells: Effect of Solvent Content.

Proton exchange membranes (PEMs) with superior characteristics are needed to advance fuel cell technology. Nafion, the most used PEM in direct methanol fuel cells (DMFCs), has excellent proton conductivity but suffers from high methanol permeability and long-term performance degradation. Thus, this study aimed to create a healable PEM with improved durability and methanol barrier properties by combining sulfonated poly(ether ether ketone) (SPEEK) and poly-vinyl alcohol (PVA). The effect of changing the N,N-dimethylacetamide (DMAc) solvent concentration during membrane casting was investigated. Lower DMAc concentrations improved water absorption and, thus, membrane proton conductivity, but methanol permeability increased correspondingly. For the best trade-off between these two characteristics, the blend membrane with a 10 wt% DMAc solvent (SP10) exhibited the highest selectivity. SP10 also showed a remarkable self-healing capacity by regaining 88% of its pre-damage methanol-blocking efficiency. The ability to self-heal decreased with the increasing solvent concentration because of the increased crosslinking density and structure compactness, which reduced chain mobility. Optimizing the solvent concentration during membrane preparation is therefore an important factor in improving membrane performance in DMFCs. With its exceptional methanol barrier and self-healing characteristics, the pioneering SPEEK/PVA blend membrane may contribute to efficient and durable fuel cell systems.

Preparation and performance evaluation of low temperature SOEC using lithium compounds as electrodes

Previous studies have found that in ceramic fuel cells using Ni0·8Co0·15Al0·05LiO2 (NCAL) as the electrode, lithium compounds such as LiOH generated by reduction of NCAL anode by H2 diffuse into oxide electrolyte membranes such as Gd0.1Ce0·9O2 (GDC), and the “GDC-lithium compounds” composite electrolyte formed online is an excellent proton conductor. In this paper, the low-temperature electrolysis performance of proton conductor type solid oxide electrolysis cell (P-SOEC) with GDC as electrolyte and NCAL as electrode for direct electrochemical conversion of H2O into H2 was investigated. It is found that at operation temperature of 550 °C, the current density of the SOEC prepared in this paper can reach 2.263 A cm−2 at 1.6 V. The composite electrolyte in the electrolysis cell reaches an ionic conductivity of 0.572 S cm−1 in the SOEC mode. The excellent hydrogen production performance proves that this new type of electrolysis cell with lithium compounds as electrodes is a promising and potential proton conductive low-temperature SOEC.

A Multifunctional Co-Based Metal-Organic Framework as a Platform for Proton Conduction and Ni trophenols Reduction.

The design and development of proton conduction materials for clean energy-related applications is obviously important and highly desired but challenging. An ultrastable cobalt-based metal-organic framework Co-MOF, formulated as [Co2(btzip)2(μ2-OH2)] (namely, LCUH-103, H2btzip = 4, 6-bis(triazol-1-yl)-isophthalic acid) had been successfully synthesized via the hydrothermal method. LCUH-103 exhibits a three-dimensional framework and a one-dimensional microporous channel structure with scu topology based on the binuclear metallic cluster {Co2}. LCUH-103 indicated excellent chemical and thermal stability; peculiarly, it can retain its entire framework in acid and alkali solutions with different pH values for 24 h. The excellent stability is a prerequisite for studying its proton conductivity, and its proton conductivity σ can reach up to 1.25 × 10-3 S·cm-1 at 80 °C and 100% relative humidity (RH). In order to enhance its proton conductivity, the proton-conducting material Im@LCUH-103 had been prepared by encapsulating imidazole molecules into the channels of LCUH-103. Im@LCUH-103 indicated an excellent proton conductivity of 3.18 × 10-2 S·cm-1 at 80 °C and 100% RH, which is 1 order of magnitude higher than that of original LCUH-103. The proton conduction mechanism was systematically studied by various detection means and theoretical calculations. Meanwhile, LCUH-103 is also an excellent carrier for palladium nanoparticles (Pd NPs) via a wetness impregnation strategy, and the nitrophenols (4/3/2-NP) reduction in aqueous solution by Pd@LCUH-103 indicated an outstanding conversion efficiency, high rate constant (k), and exceptional cycling stability. Specifically, the k value of 4-NP reduction by Pd@LCUH-103 is superior to many other reported catalysts, and its k value is as high as 1.34 min-1 and the cycling stability can reach up to 6 cycles. Notably, its turnover frequency (TOF) value is nearly 196.88 times more than that of Pd/C (wt 5%) in the reaction, indicating its excellent stability and catalytic activity.

Continuous Ultrathin Zwitterionic Covalent Organic Framework Membrane Via Surface-Initiated Polymerization Toward Superior Water Retention.

Efficient construction of proton transport channels in proton exchange membranes maintaining conductivity under varied humidity is critical for the development of fuel cells. Covalent organic frameworks (COFs) hold great potential in providing precise and fast ion transport channels. However, the preparation of continuous free-standing COF membranes retaining their inherent structural advantages to realize excellent proton conduction performance is a major challenge. Herein, a zwitterionic COF material bearing positive ammonium ions and negative sulphonic acid ions is developed. Free-standing COF membrane with adjustable thickness is constructed via surface-initiated polymerization of COF monomers. The porosity, continuity, and stability of the membranes are demonstrated via the transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) characterization. The rigidity of the COF structure avoids swelling in aqueous solution, which improves the chemical stability of the proton exchange membranes and improves the performance stability. In the higher humidity range (50-90%), the prepared zwitterionic COF membrane exhibits superior capability in retaining the conductivity compared to COF membrane merely bearing sulphonic acid group. The established strategy shows the potential for the application of zwitterionic COF in the proton exchange membrane fuel cells.

Construction of Hydration Layer for Proton Transport by Implanting the Hydrophilic Center Ag0 in Nickel Metal-Organic Frameworks.

The directional arrangement of H2O molecules can effectively regulate the ordered protons transfer to improve transport efficiency, which can be controlled by the interaction between materials and H2O. Herein, a strategy to build a stable hydration layer in metal-organic framework (MOF) platforms, in which hydrophilic centers that can manipulate H2O molecules are implanted into MOF cavities is presented. The rigid grid-Ni-MOF is selected as the supporting material due to the uniformly distributed cavities and rigid structures. The Ag0 possesses potential combination ability with the hydrophilic substances, so it is introduced into the MOF as hydration layer centers. Relying on the strong interaction between Ag0 and H2O, the H2O molecules can rearrange around Ag0 in the cavity, which is intuitively verified by DFT calculation and molecular dynamics simulation. The establishment of a hydration layer in Ag@Ni-MOF regulates the chemical properties of the material and gives the material excellent proton conduction performance, with a proton conductivity of 4.86×10-2 Scm-1.

Proton Exchange Membrane with Excellent Proton Conductivity and Superior Stability for Application at High Operating Temperatures

Proton Exchange Membrane with Excellent Proton Conductivity and Superior Stability for Application at High Operating Temperatures

Efficient Proton Conductor Based on Bismuth Oxide Clusters and Polyoxometalates.

Developing new solid-state electrolyte materials for improving the proton conductivity remains an important challenge. Herein, a novel two-dimensional layered solid-state proton conductor Bi2O2-SiW12 nanocomposite, based on silicotungstic acid (H4SiW12O40) and Bi(NO3)3·5H2O, was synthesized and characterized. The composite consists of a layered cation framework [Bi2O2]2+ and interlayer-embedded counteranionic [SiW12O40]4-, which forms continuous hydrogen bond (O-H···O) networks through the interaction of adjacent oxygen atoms on the surface of the [Bi2O2]2+ and oxygen atoms of the H4SiW12O40. Facile proton transfer along these pathways endows the Bi2O2-SiW12 (30:1) nanocomposite with an excellent proton conductivity of 3.61 mS cm-1 at 90 °C and 95% relative humidity, indicating that the nanocomposite has good prospects as a highly efficient proton conductor.