Proton Conductivity Measurements Research Articles

Comprehensive study on dielectric properties and proton conductivity of graphene oxide (GO) embedded PVdF/PVP membrane electrolytes

This article investigates how the presence of polyvinylpyrrolidone (PVP) affects the dielectric properties and proton conductivity of phosphoric acid (PA) doped PVdF/PVP-based composite polymer electrolytes supported by graphene oxide (GO). In the study, insights into the structural, morphological, and thermal characteristics of the proposed composite electrolytes are obtained using characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Proton conductivity and dielectric measurements are carried out across a frequency and temperature range (20 Hz-1 MHz, 300–420 K). We conduct in-depth discussions on the dielectric properties, including AC conductivity (σac), dielectric permittivity (ε′), imaginary permittivity (ε″), and loss tangent (tanδ) of the polymer electrolytes. While GO enhances the thermomechanical properties, the highest proton conductivity values are observed for (PVdF70/PVP30)-GO and (PVdF50/PVP50)-GO electrolytes, reaching 4.4 × 10−5 and 6.1 × 10−4 S/cm respectively. The dielectric measurements revealed a significant increase in the dielectric constant (ε′) and dielectric loss (ε″) values for the composite membranes, especially at lower frequencies and higher temperatures. For instance, the (PVdF50/PVP50)-GO composite exhibited ε′ values of 8.8 × 106, 1.99 × 105, and 77.38 at frequencies of 20 Hz, 1 kHz, and 1 MHz, respectively, at 300 K, and 7.38 × 106, 2.76 × 104, and 430.5 at 420 K. The ε″ values at 300 K for the same composite were 16.18 × 106, 7.25 × 105, and 1.09 × 103, respectively, at the same frequencies. (PVdF50-PVP50)-GO exhibits the lowest relaxation time (τ) and the highest proton conductivity at ambient temperature. These findings underscore the intricate interplay between PVP content, dielectric properties, and proton conductivity, providing valuable insights for the advancement of polymer electrolyte materials. This study contributes to our understanding of PA-doped (PVdFx/PVPy)-GO electrolytes, with implications for electronic and energy storage devices.

Proton-conduction under mild humid conditions in [NH4][M(HCOO)3] (M=Mn2+, Co2+) frameworks

Room temperature proton conduction was investigated in ammonium-based formate frameworks [NH4][M(HCOO)3] (M = Mn2+, Co2+) well-known for their ferroelectric and magnetic properties at low temperature. The synthesis was achieved through mechanosynthesis and proton conduction measurements were performed in ambient as well as in humidity and temperature controlled conditions. The proton conduction is activated by reaching the relative humidity (RH) limit of 50 % for both compounds. At 294 K a maximal conductivity of 2.2 ± 0.3 × 10−4 S/cm is observed for [NH4][Mn(HCOO)3] under RH = 70 %. The lack of proton conduction behavior in the isostructural compound Cs [Mn(HCOO)3] corroborates the role played by the NH4+ units as proton vehicle.

Hydrophilic phthalocyanine covalent organic frameworks for enhanced electrocatalytic H2O2 production

The electrocatalytic 2e− oxygen reduction reaction (ORR) is considered as a promising pathway to replace conditional anthraquinone process for hydrogen peroxide (H2O2) manufacture. However, the efficient electrocatalysts towards 2e− ORR remain urgently desired. Herein, hydrophilic two-dimensional cobalt phthalocyanine (CoPc) covalent organic frameworks (COFs), denoted as CoPc-2SO3H-COF and CoPc-SO3H-COF, were afforded via the imidization reaction of 2,3,9,10,16,17,23,24-octacarboxyphthalocyaninato cobalt(II) with hydrophilic building blocks 2,5-diaminobenzenesulfonic acid and 1,4-benzenedisulfonic acid, respectively. Powder X-ray diffraction, transmission electron microscope, and N2 sorption experiment results reveal the crystalline and porous structure of these two COFs. Moreover, the water contact angle and proton conduction measurements demonstrate the hydrophilic properties of these two COFs owing to the introduction of −SO3H into their skeleton. This, in combination with the high-efficiency active Co-N4 sites towards 2e− ORR, endows these two COFs with enhanced 2e− ORR activity in the aqueous electrolyte. In particular, CoPc-2SO3H-COF exhibits outstanding electrocatalytic H2O2 production performance with a stable H2O2 selectivity of 88.3 % under a high current density of 125 mA cm−2 for 20 h in a flow cell.

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.

(Invited) Challenges and Opportunities for the Computational Analysis of Electrochemical Energy Systems

Electrochemical systems are challenging to analyze and design due to their multi-dimensional, time-dependent, and multi-physics nature. For this reason, many computational electrochemical system models have been developed in the past three decades, some of which can now be found in commercial software packages, e.g., COMSOL or ANSYS Fluent. These models however: i) are based on simplifying assumptions, e.g., reduced dimensionality, infinite dilution, Tafel kinetics; ii) contain uncertain input parameters, e.g., effective transport properties and kinetic parameters; and, iii) are only validated with a limited number of experiments, e.g., polarization curves. These limitations, understandable at the time due to limited computational resources, characterization techniques, and material understanding and stability, are difficult to justify today that parallel programming and computer clusters enable scientists to perform large multi-dimensional simulations; electrochemical testing has expanded to include segmented cell testing, impedance spectroscopy, water flux estimation, and in-operando visualization; and, characterization tools and techniques have been developed to, for example, easily measure adsorption isotherms, effective proton conductivity and, within a given resolution, visualize the three-dimensional microstructure of the electrodes.Scientists working on computational analysis of electrochemical systems must acknowledge that further model development is still needed and must take advantage of new resources to improve the robustness and accuracy of cell-level models. The path is long and crooked, but it is very likely that the opportunity for a truly useful computational model, one that can be used for design, is beyond simplistic implementations and polarization curves. The effort is great, but it can be minimized by concurrent software development, as well as, by careful experimental work dedicated to parameter estimation and model validation.This presentation aims at outlining the limitations of state-of-the-art models, the challenges and opportunities of concurrent development and maintenance of a multi-scale, transient electrochemical energy system software, such as the open-source fuel cell simulation toolbox (OpenFCST) [1], and the new opportunities provided by combining advanced characterization tools with computational analysis. As an example, the development and validation of the transient, two-phase fuel cell and electrolyzer cell-level models in OpenFCST will be discussed [2]. The use of a hydrogen-pump model to study the effect of an active catalyst in CL effective proton conductivity measurements will also be discussed as an example of concurrent experimental/model design [3].

Achieving better balance on the mechanical stability and conduction performance of sulfonated poly(ether ether ketone) proton exchange membranes through polydopamine/polyethyleneimine co-modified poly(vinylidene fluoride) nanofiber as support

In this work, the polyvinylidene fluoride (PVDF) electrospun fibers was applied as robust mechanical support and subsequently functionalized with polydopamine/polyethyleneimine (PDA/PEI) composite, then filled with sulfonated poly (ether ether ketone) (SPEEK) to obtain SPEEK-PDA/PEI@PVDF composite proton exchange membranes. The composite membranes achieved better balance on the mechanical stability and conduction performance, owing to enhanced interface interactions and compatibility between robust PVDF and conductive SPEEK. In wet conditions, the composite membrane exhibited excellent mechanically robust with tensile strength of 34 MPa and elongation at break of almost 200 %. Furthermore, the composite membranes also showed high structure and performance stability during the measurement of proton conductivity and fuel cell performances, it could hold stable proton conductivity of 48 mScm−1 (at 80 °C) and maximum power density of 58.9 mWcm−2. The durability test further confirmed the super operating stability of composite membrane, only 2.6 % reduction in open circuit voltage was observed during operated at 80 °C for 100 h.

Dielectric behavior and proton conductivity of ultrasound-assisted graphene oxide/sulfonated poly(ether ether ketone) composite electrolytes

This work deals with the evaluation of proton conductivity and dielectric measurements of graphene oxide (GO) doped sulfonated poly(ether ether ketone) (SPEEK) electrolytes for electrochemical devices. SPEEK-GO composite electrolytes were successfully prepared via ultrasound-assisted solution casting method. FTIR, SEM, and TGA analysis were performed to characterize the GO, SPEEK matrix, and current SPEEK-GO electrolytes. Additionally, the effects of GO loading on the proton conductivity and the dielectric behavior were also studied. The effectiveness of the oxy-groups in the GO structure for proton conduction via the Grotthus mechanism was demonstrated, and the SPEEK-GO-(10.0) composite electrolyte had the highest observed proton conductivity value of 4.79 × 10−3 S/cm. This value is roughly four times greater than the proton conductivity value of the pure SPEEK polymer matrix under the same conditions (400 K, 1 MHz), which is 1.23 × 10−3 S/cm. GO was able to increase the dielectric constant (ε′) both through its large surface area and aspect ratio and through its polar functional groups, which can interact with the SPEEK polymer matrix. The decrease in the electric modulus (M′) of the SPEEK-GO-(10.0) composite with increasing temperature could be attributed to both the decrease in the complex modulus and the formation of voids and gap at the interface between the polymer matrix and the GO particles.

Structural Regulation of Two Polyoxometalate-Based Metal-Organic Frameworks for the Heterogeneous Catalysis of Quinazolinones.

Two dimeric {ε-Zn4PMo12}-based metal-organic frameworks (MOFs), [ε-PMo8VMo4VIO34(OH)6Zn4][LO] (SDUT-21, LO = [5-((4'-carboxybenzyl)oxy)isophthalic acid]) and [TBA]3[ε-PMo8VMo4VIO37(OH)3Zn4][LN] (SDUT-22, TBA+ = tetrabutylammonium ion, LN = [5-((4-carboxybenzyl)imino)isophthalic acid]), combining the advantages of polyoxometalates (POMs) and MOFs, were synthesized by the one-pot assembly strategy. The dimeric {ε-Zn4PMo12} units act as nodes that are linked by the flexible ligands and extended into two- or three-dimensional frameworks. The cyclic voltammetry and proton conductivity measurements of SDUT-21 and SDUT-22 were performed and indicated the high electron and proton transfer abilities. These materials also e xhibited the catalytic performance for the synthesis of quinazolinones in the heterogeneous state, and the different binding capacities toward the substrates caused the catalytic activity of SDUT-21 to be higher than that of SDUT-22 under the same conditions. In addition, the used catalysts could be readily recovered for five successive cycles and maintained high catalytic efficiency.

Aminosilica-Functionalized Co3O4 Nanostructures in Proton Exchange Mixed Matrix Membranes for Enhanced Separation Efficiency of Direct Methanol Fuel Cells

This work reports the alterations in the performance and morphology of a Nafion-based proton exchange membrane in the presence of three nano-Co3O4 morphologies (nanorod (R), nanosphere (S), and nanooctahedral (O)) modified by tetraethylorthosilicate (TEOS, T) and 3-aminopropyltriethoxysilane (APTES, A). The effects of surface chemistry and morphology of Co3O4 nanostructures on the properties of the as-prepared nanocomposite membranes were investigated by water uptake, proton conductivity, methanol permeability, and selectivity measurements. The methanol barrier properties of all nanocomposite membranes improved compared to the control Nafion membrane. The Nafion membranes embedded with aminosilica-functionalized Co3O4 also showed higher proton conductivity and improved methanol barrier properties compared to silica-functionalized Co3O4 and unmodified nanoparticles owing to the strong interaction between amino functionals on the surface of Co3O4 nanostructures and sulfonic moieties of the Nafion matrix. In particular, the incorporation of 5 wt % octahedral aminosilica-functionalized Co3O4 into the Nafion matrix provided the highest selectivity (15.2 × 104 S s–1 cm–3) and the lowermost methanol permeability (5 × 10–7 cm2 s–1), which were 3.6-fold higher and four times lower than that of the control Nafion membrane, respectively.

Study of high‐temperature proton exchange membrane through one‐step encapsulation of ionic liquid in sulfonated poly(ether ether ketone)

AbstractThe proton exchange membrane (PEM) is the core component of a high‐performance proton exchange membrane fuel cell (PEMFC). Since the traditional PEM has the disadvantages of poor cell performance and high cost, a new kind of PEM with good proton conductivity, low cost and simple preparation should be explored. In this paper, several different binary hybrid membranes were successfully prepared through one‐step encapsulation of different ionic liquids (ILs) in sulfonated poly(ether ether ketone) (SPEEK). The prepared membranes were characterized by scanning electron microscope (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), proton conductivity measurements and dynamic mechanical analysis (DMA). SEM images showed that ILs were fully doped into SPEEK. FT‐IR and XPS proved that SPEEK and IL formed a new chemical bond combined with intermolecular hydrogen bonds. The TG results showed that the binary hybrid membranes could maintain stability even at 300°C. The water uptake and swelling ratio showed that the water absorption capacity of the binary composite membrane played a vital role in improving proton conductivity. The proton conductivity study showed that ILs doping also helped to improve the proton conductivity of the SPEEK membrane. When the doping amount of IL was maintained at 30 wt.%, it has the highest proton conductivity, 25 mS cm−1 at 120°C. It was proved that anhydrous hybrid membrane tetraphenyl imidazole sulfate/SPEEK ([IM2][H2PO4]/SPEEK) could be used in PEMFC at medium temperature.

Design of Dual Purpose Fe‐metallogel for Magnetic Refrigeration and Fabrication of Schottky Barrier Diode

AbstractThe impetus for the present work was to design multifunctional inorganic materials that can be utilized in their original as‐synthesized state of the matter. Accordingly, we have successfully designed a benzene‐tricarboxylic acid based dual‐purpose Fe‐metallogel that can be used as an efficient material for cryogenic magnetic cooling as well as electronic device fabrication as Schottky barrier diode in their original gel state. The metallogel shows remarkable mechanical strength, self‐sustainability and thixotropic behaviour. The gel sample has been thoroughly characterized using IR, UV‐Vis spectroscopy, SEM, TEM, AFM techniques, XPS and Mössbauer spectroscopy. The porous nature, which forms the basis of the current gel based MCE study and SBD fabrication, was confirmed with gas sorption data. The porous metallogel network with by‐default entrapped anion and protic solvents of the fabricated electrical device provides an excellent platform for charge transportation with a corroborating conductivity value of 4.53×10−6 Sm−1. As if to complement the notion of multifunctional material, the magnetic studies on the Fe‐gel show significant cryogenic magnetic cooling behaviour. The theoretical result calculated using DFT are found to be highly consistent with the experimental results of the metallogel. Furthermore, we have evaluated the potential of the compound as a fuel cell membrane with detailed proton conductivity measurements on the xerogel, showing an encouraging value of 4.58×10−4 S/cmat 95 % relative humidity and 75 °C temperature.

Toward Improved Polymer Electrolyte Membranes in a High Temperature, Low Relative Humidity Environment

Previous studies on Polymer Electrolyte Membranes have shown that sulfonated polymers exhibit high thermal stability and mechanical properties. The proton conductivity of the sulfonated polymer is strongly dependent upon the degree of sulfonation, where it increases with increasing degree of sulfonation. Also, some observations suggest that densely packed sulfonate groups confer some advantages in allowing more mobile water and protons in the low water content range. In this study bisphenol-based polymers were modified by adding sulfone-amides to form a ball of sulfonates (BOS). Thin, ductile films of the membrane are fabricated by the solution casting method, which resulted in membranes with a thickness of approximately 50 mm. The synthesized copolymers and membranes are characterized by 1 H NMR, FT-IR, ion exchange capacity, water uptake, specific density and proton conductivity measurements. The water uptake and proton conductivity of the membranes are analyzed to determine the impact of varying degrees of sulfonation and side -chains groups within the modified Bisphenol based membranes. Conductivity was tested over a range of temperatures and relative humidity levels simulating potential operating conditions. Water sorption was tested over a range of relative humidity levels to gain an understanding of how relative humidity affects membrane hydration, which is one of the primary factors determining the rate of proton transport in the membrane. In addition, specific density was also measured as density offers insight into membrane hydration and polymer morphology and allows assessment of the mobility of the charge carriers. By studying membranes in this fashion, their performance can be objectively assessed in a controlled environment prior to testing in PEM fuel cells.

Direct measurement of proton conductivity of a single ionomer nanofiber

The capability of measuring the ion conductivity of ionomer nanofibers, enabling bottom-up improvement of many clean energy technologies, e.g., polymer electrolyte fuel cells, remains a great challenge due to the difficulties in fixing the sample nondestructively and eliminating the interference from contact impedance and substrate. Herein, we developed a measurement system to tackle this challenge by employing a microelectrode chip and a novel sample welding strategy. The microelectrode chip consists of four Au probes and a cavity in the center. The four-probe setup eliminates the contact impedance and any interfacial effect from the current-carrying electrodes. The central cavity enables the suspension of the tested nanofiber, thereby excludes the substrate interference. The suspended fiber is welded to the probes by the same solution of tested nanofiber under optical microscopy, so that intimate and tight junctions can be formed between the sample and Au probes. Compared to commonly used nano-welding method using electron-beam-induced deposition, this self-welding method can avoid the electron irradiation damage to the delicate sample under test. The measured proton conductivity with the developed system possesses high accuracy and gives insights into the proton conduction mechanism of ionomer nanofibers. Furthermore, the proposed method can be applied to other ionic conductive nanofibers or nanofilms.

Integrated Thermo-Electric Measurement of Electrospun Nanofiber for Polymer Electrolyte Fuel Cell

Polymer electrolyte fuel cell (PEFC), as an efficient hydrogen energy conversion device, has been developed for decades. Catalyst layer (CL), where the oxygen reduction reaction occurs, predominantly determines the performance of PEFC. Since 1889, the mass activity of catalyst layer has been improved for more than three orders of magnitudes, thanks to the invention of PFSA ionomer and highly dispersed catalyst on nano-sized carbon support. In recent years, introducing order into CL is bringing the CL performance to a higher level. The CLs with state-of-the-art performance feature nanofiber structures. One type of is ionomer nanofibers deposited with Pt/C catalyst on the surface, and another type is composite nanofiber containing ionomer, Pt/C catalyst, and binding polymer. Their superior performance may come from the ordered mass transport network and the size effect of nanofiber conductivity. To further improve the CL performance, the structure-property-performance relationship of ionomer nanofibers or composite nanofibers needs to be clarified.In this work, we designed a setup to measure the proton, electron and thermal conductivity as well as the performance of a single ionomer or composite nanofiber. We developed a self-bonding method to fix the nanofiber on the micro-electrode. For proton and electron conductivity measurement, four-probe method was adopted to eliminate the electrical contact resistance and interfacial effect. For thermal conductivity measurement, Raman assisted steady state method was used to directly measure the temperature profile along the nanofiber. So, the measurement error resulting from the thermal contact resistance between the sample and the temperature sensor/heat sink can be eliminated. For performance measurement, three-electrode system was adopted using the Ag/AgCl electrode as the reference electrode and the Zn/ZnCl2 electrode as the counter electrode. We prepared nanofibers with different size, polymer content, and cross-sectional component distribution by controlling the ink recipe and electrospinning parameters. The integrated thermo-electric measurement found that the proton and thermal conductivity of nanofiber are one order of magnitude higher than bulk properties and increases with decreasing fiber radius. This is attributed to the oriented ionic morphology along the nanofiber. Furthermore, a nanofiber model was developed to extract the catalytic activity and gas diffusion coefficient of nanofiber. These characterization and modelling work can provide guidance to the design and optimization of catalyst layer with electrospun ionomer or composite nanofibers.

Introduction of a crystalline block as a strategy to increase swelling resistance and dimensional stability of sulfonated copolyimide

AbstractThe introduction of blocks inclined to form areas of high crystallinity into the sulfonated block co‐polyimide is investigated as a prospective strategy to increase swelling resistance and dimensional stability of the polymer in application to the proton exchange membranes development. The novel copolymer with the highly crystalline block was obtained and characterized by the means of static and dynamic light scattering, IR spectroscopy, thermal gravimetric analysis and differential scanning calorimetry. The structural and morphological features of the obtained copolymer were investigated with X‐ray diffraction analysis and atomic force microscopy. Transport properties of the co‐polyimide are evaluated in terms of pervaporation, proton conductivity measurements and dielectric spectroscopy experiments. The article aims at the evaluation of the influence of the high‐crystalline block introduction on morphological, transport and physical properties of the sulfonated copolymer. The properties of the obtained crystalline sulfonated copolymer are compared to the ones of the similar amorphous polyimide. The studied crystalline copolymer showed constancy of the proton conductivity values in the broad range of temperatures (20–120°C, RMSD of 0.23%) and relative humidity values.

Development of 1,2,3-Triazole Based Ionic Liquid Doped Sulfonated Polysulfone (SPSU) Electrolytes for Anhydrous Proton Exchange Membrane Applications

In this study, triazole based ionic liquid doped sulfonated polysulfone (SPSU) composite membranes were evaluated for high temperature proton exchange membrane fuel cell (PEMFC) systems. SPSU obtained by sulfonation of aromatic polysulfone (PSU) polymer matrix was used in the preparation of composite electrolytes. Sulfonated polymer matrices were doped with three different triazole-based ionic liquids (TIL-1, TIL-2 and TIL-3) synthesized within the scope of the study and composite membrane series were formed. Structural, thermal and mechanical characterizations were performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), respectively. Proton conductivities were measured over a wide temperature range (380-450 K) and the effectiveness of composite membranes in high temperature PEMFC systems was evaluated. As a result of TGA analysis, all triazole based ionic liquid doped membrane series exhibited high thermal resistance. It was observed that the proton conductivity of the composite structures was greatly improved with high temperature proton conductivity measurements (8.05 mS/cm for SPSU; 58.1 mS/cm for SPSU/TIL-3(1.0)) and the obtained membranes could be an alternative in high temperature PEMFCs.

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO 3 H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm 2 was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm 2 was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications. • This study proposes PBI/sGO as an alternative membrane for HT-PEMFC application. • SGO was revealed as an effective filler for a PBI composite membrane for HT-PEMFC. • PBI/sGO membranes possess high proton conductivity. • PBI/sGO membrane with 5% GO content is a potential electrolyte for HT-PEMFC.

A Preinstalled Protic Cation as a Switch for Superprotonic Conduction in a Metal-Organic Framework.

Metal–organic frameworks (MOFs), made from various metal nodes and organic linkers, provide diverse research platforms for proton conduction. Here, we report on the superprotonic conduction of a Pt dimer based MOF, [Pt2(MPC)4Cl2Co(DMA)(HDMA)·guest] (H2MPC, 6-mercaptopyridine-3-carboxylic acid; DMA, dimethylamine). In this framework, a protic dimethylammonium cation (HDMA+) is trapped inside a pore through hydrogen bonding with an MPC ligand. Proton conductivity and X-ray measurements revealed that trapped HDMA+ works as a preinstalled switch, where HDMA+ changes its relative position and forms an effective proton-conducting pathway upon hydration, resulting in more than 105 times higher proton conductivity in comparison to that of the dehydrated form. Moreover, the anisotropy of single-crystal proton conductivity reveals the proton-conducting direction within the crystal. The present results offer insights into functional materials having a strong coupling of molecular dynamic motion and transport properties.

Development and performance analysis of polybenzimidazole/boron nitride composite membranes for high‐temperaturePEMfuel cells

In this research, polybenzimidazole/boron nitride (PBI/BN) based composite membranes have been prepared for high-temperature PEM fuel cell (HT-PEMFC). BN was preferred because of its superior thermal robustness, high chemical stability, non-conductor property, and high plasticizer characteristic. The loading of BN in the composite membrane was studied between 2.5 to 10 wt%. The composite membranes were characterized using TGA, DSC, XRD, SEM, mechanical tests, acid doping/leaching, and proton conductivity measurements. The highest conductivity of 0.260 S/cm was found for PBI/BN-2.5 membrane at 180°C. It has been determined that the PBI/BN-2.5 membrane has higher performance than the PBI membrane according to the HT-PEMFC tests performed with Hydrogen and dry air. The heightened HT-PEMFC performance can be ascribed to interactive effects between BN particles and the PBI polymer matrix. PBI/BN composite membranes show a good perspective in the high-temperature PEMFC applications.

Structure, Luminescent Sensing and Proton Conduction of a Boiling-Water-Stable Zn(II) Metal-Organic Framework.

A novel Zn(II) metal-organic framework [Zn4O(C30H12F4O4S8)3]n, namely ZnBPD-4F4TS, has been constructed from a fluoro- and thiophenethio-functionalized ligand 2,2′,5,5′-tetrafluoro-3,3′,6,6′-tetrakis(2-thiophenethio)-4,4′-biphenyl dicarboxylic acid (H2BPD-4F4TS). ZnBPD-4F4TS shows a broad green emission around 520 nm in solid state luminescence, with a Commission International De L’Eclairage (CIE) coordinate at x = 0.264, y = 0.403. Since d10-configured Zn(II) is electrochemically inert, its photoluminescence is likely ascribed to ligand-based luminescence which originates from the well-conjugated system of phenyl and thiophenethio moieties. Its luminescent intensities diminish to different extents when exposed to various metal ions, indicating its potential as an optical sensor for detecting metal ion species. Furthermore, ZnBPD-4F4TS and its NH4Br-loaded composite, NH4Br@ZnBPD-4F4TS, were used for proton conduction measurements in different relative humidity (RH) levels and temperatures. Original ZnBPD-4F4TS shows a low proton conductivity of 9.47 × 10−10 S cm−1 while NH4Br@ZnBPD-4F4TS shows a more than 25,000-fold enhanced value of 2.38 × 10−5 S cm−1 at 40 °C and 90% RH. Both of the proton transport processes in ZnBPD-4F4TS and NH4Br@ZnBPD-4F4TS belong to the Grotthuss mechanism with Ea = 0.40 and 0.32 eV, respectively.