Proton Conductivity Performance Research Articles

Sulfonated graphene oxide‐doped proton conductive membranes based on polymer blends of highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole

ABSTRACTSimultaneously improving the proton conductivity and mechanical properties of a polymer electrolyte membrane is a considerable challenge in commercializing proton exchange membrane fuel cells. In response, we prepared a new series of miscible polymer blends and thus the corresponding crosslinked membranes based on highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole. The blended membranes showed more compact structures, due to the acid‐base interactions between the two constituents, and improved mechanical and morphological properties. Further efforts by doping sulfonated graphene oxide (s‐GO) forming composite membranes led to not only significantly elevated proton conductivity and electrochemical performance, but also better mechanical properties. Notably, the composite membrane with the filler content of 15 wt % exhibited a proton conductivity of 0.217 S cm−1 at 80 °C, and its maximum power density tested by the H2/air single PEMFC cell at room temperature reached 171 mW cm−2, almost two and half folds compared with that of the native membrane. As a result, these polymeric membranes provided new options as proton exchange membranes for fuel‐cell applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46547.

Hybrid electrolyte SiW9MoV2/rGO/SPEEK for solid supercapacitors with enhanced conductive performance

To improve the proton conductive performance of heteropoly acids, a novel proton-conducting hybrid electrolyte SiW9MoV2/rGO/SPEEK was prepared by a simple and effective method based on sulfonated polyether ether ketone (SPEEK), H6SiW9MoV2O40 (SiW9MoV2) and reduced graphene oxide (rGO) in this work. This hybrid material was characterized by IR, TEM and XRD. Electrochemical impedance spectroscopy shows the obtained SiW9MoV2/rGO/SPEEK electrolyte exhibits an appreciable proton conductivity of 1.07 × 10−2 S cm−1 at 16 °C and 70% relative humidity, which increases with higher temperature, and the activation energy for proton conduction of this hybrid film is 17.82 kJ mol−1. The proton conduction is speculated to be the mixing of Grotthuss mechanism and Vehicle mechanism that accelerate the proton mobility in the hybrid electrolyte. This work lays a foundation in the field of HPAs-based separator films for proton exchange membrane devices and solid supercapacitors.

Polybenzimidazole (PBI-OO) based composite membranes using sulfophenylated TiO2 as both filler and crosslinker, and their use in the HT-PEM fuel cell

Crosslinked metal oxide containing nanocomposite membranes, in which the filler also acts as crosslinker, were prepared by blending polybenzimidazole (PBI-OO) and phenylsulfonated TiO2 particles (s-TiO2). Thermal curing changes the ionically crosslinked system into a covalently crosslinked system. The synthesized s-TiO2 nanoparticles were analyzed by thermal gravimetric analysis and scanning electron microscopy. The covalently crosslinked nanocomposite membranes (c-sTiO2-PBI-OO) were doped with phosphoric acid (PA) for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. The membrane properties, such as PA uptake, dimensional change, gel content, proton conductivity, mechanical property, and single cell performance were evaluated and compared with the properties of acid-doped c-PBI-OO. PA doped 6-c-sTiO2-PBI-OO (6 wt% sTiO2) showed the highest uptake of 392 wt%, and a proton conductivity at 160 °C of 98 mS cm−1. In the fuel cell, a peak power density of 356 mW cm−2 was obtained, which is 76% higher than that of a c-PBI-OO based system (202 mW cm−2). To evaluate the stability of the membrane performance over time, the best performing membrane was tested for over 700 h.

Synthesis of Crystalline Porous Organic Salts with High Proton Conductivity.

Self-assembled crystalline porous organic salts (CPOSs) formed by an acid-base combination and with one-dimensional polar channels containing water molecules have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2×10-2 S cm-1 at 333 K and under high humid conditions. This is among the best conductivity values reported to date for porous materials, for example, metal-organic frameworks and hydrogen-bonded organic frameworks. These materials exhibiting permanent porosity represent a group of porous materials and may find interesting applications in proton-exchange membrane fuel cells.

Synthesis of Crystalline Porous Organic Salts with High Proton Conductivity

AbstractSelf‐assembled crystalline porous organic salts (CPOSs) formed by an acid–base combination and with one‐dimensional polar channels containing water molecules have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2×10−2 S cm−1 at 333 K and under high humid conditions. This is among the best conductivity values reported to date for porous materials, for example, metal–organic frameworks and hydrogen‐bonded organic frameworks. These materials exhibiting permanent porosity represent a group of porous materials and may find interesting applications in proton‐exchange membrane fuel cells.

Infiltration of 40SiO2−40P2O5−20ZrO2 sol-gel in sSEBS membranes for PEMFCs application

This work describes the preparation of novel and low cost hybrid organic-inorganic membranes via sol-gel chemistry and direct infiltration method using a novel inorganic precursor (40SiO2−40P2O5−20ZrO2) and sulfonated styrene-ethylene-butylene-styrene triblock copolymer (sSEBS) for their use in fuel cells (PEMFC). sSEBS shows a distinct phase separated morphology which can be used as a template to incorporate the inorganic component preferentially within the ionic domains of the polymer, improving mechanical stability and reducing water uptake. The hybrid membranes are evaluated and compared to sSEBS in terms of swelling in water, IEC and FTIR. Chemical oxidation stability has been investigated using Fenton's reagent and the morphology has been observed using FE-SEM, EDX and AFM. The electrochemical characterization in single cells was carried out at 60 °C, atmospheric pressure and 100% relative humidity in order to determine hydrogen crossover, through-plane proton conductivity and cell performance. The results show that infiltration times up to 40 min lead to hybrid membranes with lower swelling in water, enhanced dimensional stability, good proton conductivity and better cell performance than pure sSEBS.

New Composite Membrane of Carboxylated Polysulfone (CPS)– Polyphenylene Ether Ether Sulfone (PPEES) as Potential Material for Direct Methanol Fuel Cell

In the present study, carboxylated polysulfone (CPS) and Poly (1,4–phenylene ether ether–sulfone) (PPEES) NF membranes for their application in proton exchange membrane fuel cells (PEMFCs) were investigated. New NF membranes were prepared by blending PPEES with CPS solution in NMP (5 wt. %) by the solution casting procedure using K–control coater. The membranes have been characterized by thermal analysis, water uptake, IEC measurements, proton conductivity performance and methanol crossover. Electrochemical impedance spectroscopy (EIS) was at length used to decide proton conductivity. The addition of CPS increased the water uptake capability of the synthesized membrane and resulted in enhanced proton conductivity. The conductivity values in the range of 10–4 –10–2 S/cm were obtained for the new CPS–PPEES membranes. The conductivities of the membranes showed increasing trend as a function of operating temperature and wt. % of CPS. Membrane of the type CM1 gave the conductivity in the range of 0.12 S/cm at 100°C. The results showed that, CPS/PPEES is a promising membrane material for possible use in proton exchange membrane fuel cells.

Parameters effect on proton conductivity to obtain chitosan membranes for use as electrolytes in PEMFC

Summary The chitosan biopolymer can be used as a proton-conducting membrane in proton-exchange membrane fuel cell. In the forms that they have normally obtained and tested, chitosan membranes typically show poor performance in conduction of protons, requiring modifications in the structure of the biopolymer or blending with other polymers to increase its proton conductivity. The present work investigates the individual properties of chitosan and relates them to the proton conductivity performance of membranes composed of this polymer. Evaluation was made of the effects of variables such as the degree of deacetylation (DD) and the molar mass (Mv) of chitosan membranes without addition of any other polymer. The DD and Mv values of the chitosan used to produce membranes determined the proton conduction, with lower DD and higher Mv resulting in higher conductivity. The thicker membranes presented greater crystallinity, with conductivity between 2.0 × 10−4 and 1.8 × 10−3 S cm−1. The characteristic stages of degradation of the chitosan membranes were in the ranges 200 to 300°C and 500 to 600°C, indicating good thermal stability of the material.

Solution blown biofunctionalized poly(vinylidene fluoride) nanofibers for application in proton exchange membrane fuel cells

In this study, we prepared a novel type of biofunctionalized poly(vinylidene fluoride) (PVDF) nanofibers. Cysteine, a natural amino acid, was grafted onto the surfaces of PVDF nanofibers, The −SH groups of cysteine were then oxidized to −SO3H. The formation of proton-conducting pathways was induced by the −SO3H and COOH groups of the oxidized cysteine chains on the surfaces of the biofunctionalized PVDF nanofibers. Composite membranes were fabricated by impregnating the biofunctionalized PVDF nanofibers with Nafion. Then, the effects of incorporating nanofibers grafted with different amounts of oxidized cysteine on the thermal stability, water uptake dimensional stability, proton conductivity, and single-cell performance of Nafion composite membranes were investigated. The properties of the composite membranes were superior to those of the Nafion membrane. Furthermore, Nafion/PVDF–Cys-30 exhibited the highest proton conductivity of 0.22Scm−1 (80°C), and the maximum power density of 108.42mWcm−2 which was twice than the values of Nafion 117 membrane (51.2mWcm−2) at 60°C under 100% RH. The introduction of biofunctionalized nanofibers significantly improved cell performance, proton conductivity, dimensional stability, and methanol permeability of the membrane.

Effect of Methylimidazole Groups on the Performance of Poly(phenylene oxide) Based Membrane for High-Temperature Proton Exchange Membrane Fuel Cells

A series of phosphoric acid (PA) doped imidazolium poly(phenylene oxide) (PPO) membranes with different methylimidazole (MeIM) contents were prepared to tailor the performance of solid-state membranes. First, brominated poly(phenylene oxide) (BPPO) was synthesized by methyl bromination. Then BPPO was reacted with MeIM and doped with PA. The process was confirmed by Fourier transform infrared spectroscopy and 13C NMR. The PA absorption ability of the imidazolium poly(phenylene oxide) (PPO-MeIM) membranes changed with increasing MeIM content. PPO-MeIM membrane showed the best proton conductivity of 6.79 × 10–2 S cm–1 at 0% relative humidity, the highest mechanical strength of 4.8 MPa at the molar ratio of 4:10 (M-3#) at 30 °C, and high power density of 260 mW cm–2 without additional humidification at 160 °C. Results indicated that incorporation of an appropriate amount of MeIM groups can achieve the best proton conduction performance and mechanical properties.

Highly Efficient Proton Conduction in a Three-Dimensional Titanium Hydrogen Phosphate

Force field-based and ab initio molecular dynamics simulations are combined with impedance spectroscopy experiments to reveal the high proton conduction performance of a three-dimensional titanium phosphate TiIVTiIV(HPO4)4 under humidity and further elucidate the microscopic mechanism at the origin of the proton transport throughout the porosity of this solid. The molecular simulations revealed that the POH groups in the structure act as a proton source, and the proton is transported from one pore to another through the hydrogen bond network formed by water molecules and the bridging O of the solid. Propitiously, besides its superprotonic behavior with a conductivity of 1.2 × 10–3 S cm–1 at room temperature and 95% relative humidity, this material is one of the best porous solids reported to date in terms of efficiency for proton transfer with a resulting activation energy (0.13 eV) as low as that reported for Nafion commercially used as electrolyte membrane in fuel cells. Furthermore, this solid shows a ...

Novel proton exchange membrane nanocomposites based on sulfonated tungsten trioxide for application in direct methanol fuel cells

Novel sulfonated poly (phthalazinone ether ketone) (SPPEK)/sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVdF-co-HFP)/sulfonated tungsten trioxide (SWO3) nanocomposite blend membranes were fabricated as alternative proton exchange membranes (PEM) for application in direct methanol fuel cell (DMFC). PPEK and PVdF-co-HFP were sulfonated using sulfuric acid and chlorosulfonic acid, respectively. The degree of sulfonation (DS) of produced SPPEK and SPVdF-co-HFP were determined by titration method and found to be 68% and 30%, respectively. The dominant characteristics of the prepared membranes, such as water uptake, membrane swelling, proton conductivity, methanol permeability, selectivity and DMFC performance were investigated. The membranes containing SWO3 nanoparticles indicated higher proton conductivity and lower methanol permeability compared with pristine SPPEK and blend membranes. This improvement is attributed to presence of the sulfonated groups of nanoparticles that increases proton conductivity with Grotthus and vehicle mechanisms. The catalytic properties of SWO3 nanoparticles increase kinetic of reaction in interface surface of membrane and electrode and improve performance of DMFCs. Well optimized nanocomposite blend membrane (MSSW5) showed proton conductivity of 0.071 S cm−1, methanol permeability of 9.5 × 10−8 cm2 S−1 and power density of 63.60 mW cm−2 at room temperature, thus it can be a suitable candidate for DMFC application.

Proton conductive cross-linked benzoxazine-benzimidazole copolymers as novel porous substrates for reinforced pore-filling membranes in fuel cells operating at high temperatures

Proton conductive porous substrates consisting of cross-linked benzoxazine-benzimidazole copolymers are developed for practical application of reinforced pore-filling membranes in polymer electrolyte membrane fuel cells operating at high-temperatures (>100°C) and low relative humidity (<50% RH) conditions. The porous proton conductive substrates are prepared by casting solution mixtures of sodium 3-(4-sulfonatophenyl-3,4-dihydro-2H-1,3 benzoxazine-6-sulfonate (pS) and poly[2,2′-(m-phenylene-5,5′-bibenzimidazole] (PBI) with dibutyl phthalate (DBP) as a porogen, followed by subsequent stepwise heating to 220°C and extraction of DBP from the P(pS-co-BI) films. The resulting porous substrates are found to have mechanically robust cross-linked structures, tunable hydrophilicity, and proton conductivity. A pore-filling membrane is prepared by impregnating the porous substrate with sulfonated poly(arylene ether sulfone) having the degree of sulfonation of 70mol%. The pore-filling membrane exhibits much improved dimensional stability and mechanical strength compared to the linear sulfonated poly(arylene ether sulfone) membrane and its proton conductivity and cell performance are found to be superior to the pore-filling membrane prepared using the porous substrate based on cross-linked benzoxazine-benzimidazole copolymers without any proton conductive acid groups.

Mordenite/Nafion and analcime/Nafion composite membranes prepared by spray method for improved direct methanol fuel cell performance

The aim of this work was to improve proton exchange membranes (PEMs) used in direct methanol fuel cells (DMFCs). A membrane with a high proton conductivity and low methanol permeability was required. Zeolite filler in Nafion (NF matrix) composite membranes were prepared using two types of zeolite, mordenite (MOR) and analcime (ANA). Spray method was used to prepare the composite membranes, and properties of the membranes were investigated: mechanical properties, solubility, water and methanol uptake, ion-exchange capacity (IEC), proton conductivity, methanol permeability, and DMFC performance. It was found that MOR filler showed higher performance than ANA. The MOR/Nafion composite membrane gave better properties than ANA/Nafion composite membrane, including a higher proton conductivity and a methanol permeability that was 2–3 times lower. The highest DMFC performance (10.75mWcm−2) was obtained at 70°C and with 2M methanol, with a value 1.5 times higher than that of ANA/Nafion composite membrane and two times higher than that of commercial Nafion 117 (NF 117).

Nitrile functionalized graphene oxide for highly selective sulfonated poly(arylene ether nitrile)-based proton-conducting membranes

The incorporation of 4-(3-aminophenoxy)phthalonitrile grafted graphene oxide into SPEN proton-conducting membrane was proved to be an effective way to improve the interfacial interaction and proton conductivity performance.

Lanthanide derivatives of Ta/W mixed-addendum POMs as proton-conducting materials.

Four lanthanide derivatives of Ta-containing POMs [Ln3(H2O)22][P2W15Ta3O62]·nH2O (Ln = La, 1; Ce, 2; Pr, 3; and Nd, 4) were isolated by the self-assembly of Wells-Dawson type Ta/W mixed-addendum POM and lanthanide ions. Compound 1 showed excellent proton conduction performance at high relative humidities (RHs), with conductivity reaching 1.26 × 10-2 S cm-1 at 95 °C under 98% RH.

Effect of pore-directing agents in SBA-15 nanoparticles on the performance of Nafion®/SBA-15n composite membranes for DMFC

Nanoparticles of 2D hexagonal mesoporous SBA-15 silica were prepared for the first time and mixed in Nafion® to form composite membranes by solvent casting method. The SBA-15 nanoparticles containing P123 surfactant (S-SBA-15n) and that extracted with ethanol (Ex-SBA-15n) were used as the inorganic fillers in order to see the effect of pore-directing agent on the performance of resultant composite membranes. The physico-chemical properties of SBA-15 nanoparticles were examined with powder XRD, N2 sorption, TGA and SEM. The methanol permeability, proton conductivity, and cell performance of the resultant composite membranes were compared in terms of the content of SBA-15 nanoparticles and whether the pore-directing agent was removed. The optimal proton conductivities were obtained for the composite membranes with 5wt% loading of SBA-15 nano-particles. Moreover, the P123 pore-directing agent present inside the pores of S-SBA-15n was found to effectively resist methanol permeation from anode to cathode and also assist the proton transferring. The single cell assembled with 5wt% S-SBA-15n/Nafion composite membrane gave the highest power density of 117mWcm−2 at 60°C, which was about 80% higher than the cell with recast Nafion membrane and also 23% higher than that with commercial membrane of Nafion® 117.

Establishing Targets for the Cathode Catalyst Layer Kinetic & Transport Parameters in PEMFC Designs

Introduction Commercializing polymer electrolyte membrane fuel cells (PEMFC) is ultimately a matter of achieving the necessary cost for broad market penetration. Cost is a function of materials, manufacturability, performance, and durability. Performance and durability targets have been set by the DOE [1] to provide guidance and focus to the PEMFC industry for specific applications such as the automotive sector. To cascade these challenging targets down to material and transport requirements we employ a fully integrated performance model to conduct parameter optimization studies in tandem with experimental validation. Design curves are utilized as inputs to the model to provide the current state-of-the-art capability regarding catalyst activity and ionomer proton conductivity. High performing commercial membrane and GDL components were selected with a standard catalyst (Figure 1) to provide a baseline for this evaluation. The gap between modelled MEA performance and DOE targets will be highlighted and a recommended path forward will be provided. Results & Discussion Aside from catalyst activity and available surface area, the cathode catalyst layer performance is dictated by the mass transport of protons (proton conductivity), oxygen (gas diffusivity), and water (gas & liquid permeability) [2-4]. Several material sets have been evaluated experimentally in-situ to provide a range in catalyst activity, proton conductivity, and effective layer diffusivity as shown in figures 1 and 2 (diffusivity not shown). During operation the distribution of current through the porous three dimensional catalyst layer structure [6] is dictated by the catalyst activity and layer transport properties. We will describe in this work the relationship between proton conductivity and voltage performance. Based on these results we can set relevant conductivity targets, which can be used for both ionomer development and material down selection. These parameters will be utilized in the Ballard/DOE funded FC-Apollo performance model to provide the current status toward achieving the DOE’s 2020 automotive targets listed in Table 1. Further, technology gaps will be identified in conjunction with a strategy toward meeting these objectives. Acknowledgement The authors would like to acknowledge Joey Jickain for his testing support and National Resources Canada (NRCan), National Research Council of Canada (NRC-IRAP), and the US Department of Energy (DOE) for funding various aspects of this work. Reference 1. http://energy.gov/eere/fuelcells/doe-technical-targets-polymer-electrolyte-membrane-fuel-cell-components2. Egushi, M., Baba, K., Onuma, T., Yoshida, K., Iwasawa, K., Kobayashi, Y., Uno, K., Komatsu, K., Kobori, M., Nishitani-Gamo, M., Ando, T., Polymers, 4, p. 1645 (2012)3. Xie, J., Xu, F., Wood, D.L., More, K.L., Zawodzinski, T.A., Smith, W.H., Electrochimica Acta 55 p. 7404 (2010)4. Gode, P., Jaouen, F., Lindbergh, G., Lundblad, A., Sundholm, G., Electrochimica Acta 48 p. 4175 (2003)5. Young, AP., Gyenge, E., Stumper, J., J. Electrochem. Soc., 156, B913 (2009) 6. Young, AP., Knights, S., Gyenge, E., Stumper, J., J. Electrochem. Soc., 157, B425 (2010) Figure 1

Poly(p-phenylene sulfonic acid-ran-2,5-benzophenone) pore-filling membranes with highly packed acid structure and their polymer electrolyte fuel cell performances

We synthesized Poly(p-phenylene sulfonic acid-ran-2,5-benzophenone) (PPPS-BP) with high ion exchange capacity (IEC). This polymer formed a highly packed acid structure in the pores of porous thin substrates. In addition, the filled electrolyte polymer was cross-linked to obtain a practical membrane.In particular, the pores of the polyethylene microporous membrane were filled with cross-linked electrolytes with high IEC (5.1 meq g−1), derived from PPPS-BP, vinyl sulfonic acid, and triallyl isocyanurate. The membrane exhibited high proton conductivity and good single cell performance (H2/O2), equal to or higher than a commercial membrane (Nafion® HP) under a wide range of humidity conditions. The high proton conductivity appeared to be conferred by the highly packed acid structure in the membrane. The membrane also showed high mechanical durability in dry–wet cycle test. Therefore, the fabricated membrane presents as a good candidate for fuel cell applications under low relative humidity conditions.

Luminescent and Proton Conducting Lanthanide Coordination Networks Based On a Zwitterionic Tripodal Triphosphonate.

The synthesis, structural characterization, luminescence properties, and proton conduction performance of a new family of isostructural cationic 2D layered compounds are reported. These have the general formula [Ln(H4NMP)(H2O)2]Cl·2H2O [Ln = La(3+), Pr(3+), Sm(3+), Eu(3+), Gd(3+), Tb(3+), Dy(3+), Ho(3+), H6NMP = nitrilotris(methylphosphonic acid)], and contain Cl(-) as the counterion. In the case of Ce(3+), a 1D derivative, [Ce2(H3NMP)2(H2O)4]·4.5H2O, isostructural with the known lanthanum compound has been isolated by simply crystallization at room temperature. The octa-coordinated environment of Ln(3+) in 2D compounds is composed by six oxygen atoms from three different ligands and two oxygens from each bound water. Two of the three phosphonate groups act as both chelating and bridging linkers, while the third phosphonate group acts solely as a bridging moiety. The materials are stable at low relative humidity at less at 170 °C. However, at high relative humidity transform to other chloride-free phases, including the 1D structure. The proton conductivity of the 1D materials varies in a wide range, the highest values corresponding to the La derivative (σ ≈ 2 × 10(-3) S·cm(-1) at RH 95% and 80 °C). A lower proton conductivity, 3 × 10(-4) S·cm(-1), was measured for [Gd(H4NMP)(H2O)2]Cl·2H2O at 80 °C, which remains stable under the work conditions used. Absorption and luminescence spectra were recorded for selected [Ln(H4NMP)(H2O)2]Cl·2H2O compounds. In all of them, the observed transitions are attributed solely to f-f transitions of the lanthanide ions present, as the H4NMP(2-) organic group has no measurable absorption or luminescence properties.