Proton Conductivity Performance Research Articles

Non-destructive fabrication of Nafion/silica composite membrane via swelling-filling modification strategy for high temperature and low humidity PEM fuel cell

Based on the swelling-filling modification strategy, Nafion/silica composite membrane is facilely fabricated by non-destructively filling silica nano-particles into the Nafion framework. High temperature proton conductive performance of modified Nafion membrane is significantly enhanced due to the synergistic effect of maintaining the ordered nanophase-separated structure in Nafion and excellent water retention capacity of the silica fillers. Proton conductivity of the composite membrane is therefore raised to 33 mS/cm at 110 °C and 60% RH, which is enhanced by ca. 30% compared with the pristine Nafion. Taking account into the improved mechanical and oxidative stabilities attributed to the hydrogen bonding interaction between silica nano-particles and Nafion chains, high temperature fuel cell performance is measured and found to be remarkably improved by 37% at low humidity by considering the power density.

Synthesis and characterization of a novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymer proton exchange membranes.

A series of novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymers (S-SPAES(x/y)) was prepared from 4,4′-biphenol, 4,4′-difluorodiphenyl sulfone, and a new difluoro aromatic monomer 1-(2,6-difluorophenyl)-2-(3,5-dimethoxyphenyl)-1,2-ethanedione (DFDMED) via co-polycondensation, demethylation, and further nucleophilic substitution of 1,4-butane sultone. Meanwhile, quinoxaline-based crosslinked copolymers (CS-SPAES(x/y)) were obtained via cyclo-condensation between S-SPAES(x/y) and 3,3′-diaminobenzidine. Both the crosslinkable and crosslinked copolymer membranes exhibit good mechanical properties and high anisotropic membrane swelling. Crosslinkable S-SPAES(1/2) with an ion exchange capacity (IEC) of 2.01 mequiv. g−1 displays a relatively high proton conductivity of 180 mS cm−1 and acceptable single-cell performance, which is attributed to its good microphase separation resulting from the side-chain sulfonated copolymer structures. Compared with S-SPAES(1/1) (IEC of 1.68 mequiv. g−1), crosslinked CS-SPAES(1/2) with a comparable IEC exhibits a larger conductivity of 157 mS cm−1, and significantly higher oxidative stability and lower membrane swelling, suggesting a distinct performance improvement due to the quinoxaline-based crosslinking.

High temperature anhydrous proton exchange membranes based on chemically-functionalized titanium/polybenzimidazole composites for fuel cells

We herein report an effective way to fabricate high-performance polybenzimidazole (PBI) nanocomposite membranes using sulfophenylated titanium oxide (s-TiO2) nanoparticles for application in high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The s-TiO2, multifunctional inorganic proton conductors that can improve proton conductivity and cell performance of PBI, was obtained through the surface modification. The PBI nanocomposite membranes were doped with phosphoric acid (PA) for performance evaluation. Properties such as PA doping level, proton conductivity, PA retention and cell performance were evaluated and compared to neat PBI. PA doped PBI-sTP2 (2 wt% TiO2) showed the highest doping of 12.1 and proton conductivity of 0.096 S/cm at 150 °C. In the cell test, peak power density of 621 mW/cm2 was obtained, roughly 30% better performance compared to neat PBI (471 mW/cm2).

Preparation and Characterisation of Composite Sulfonated Polyether Ether Ketone for Direct Methanol Fuel Cells

Direct Methanol Fuel Cell (DMFC), uses a proton exchange polymer electrolyte which one of the key components developed to realize the commercialization of fuel cells in transportation and portable equipment. Poly Ether Ether Ketone (PEEK) is a thermoplastic material that has a combination of physico-chemical and good mechanical properties. The introduction of cesium tungstophosphoric acid (Cs-PWA) into the polymer matrix is an easy strategy to improve the properties of sulfonated PEEK. This research aims to study the effect of amount Cs-PWA loading in the fabrication of sulfonated PEEK on the membrane characteristics such as FTIR and XRD analysis, water uptake, methanol permeability, and proton conductivity. The results indicated that sPEEK/Cs-PWA membranes ware potential candidate as proton conductive membrane for application of DMFC due to enhancement of proton conductivity and methanol permeability performance.

Designing Carbon/Oxygen Ratios of Graphene Oxide Membranes for Proton Exchange Membrane Fuel Cells

Graphene oxide (GO), which is the oxidized form of graphene, has holes and functional groups on the surface and thus has high potential to be used as an electrochemical transport channel material. In this study, differently modified GO membranes are applied as electrolytes of proton exchange membrane fuel cells (PEMFCs) with controlled carbon/oxygen ratios. The critical and desired properties of the electrolyte, such as electron conductivity, proton conductivity, interfacial reactivity, and cell performance are evaluated in identical platinum-sputtered model electrodes. Among them, with the help of an increased concentration of oxygen-containing groups, a GO membrane with a low carbon/oxygen ratio shows a 2.9-fold improved maximum power density and advanced electrochemical properties compared with the pristine GO membrane. The characterization of GO suggests that the redox state of the membrane is an important factor for controlling the proton conductivity, interfacial reactivity, and maximum power density of PEMFCs.

Toughened polymer electrolyte membranes composed of sulfonated poly(arylene ether ketone) block copolymer and organosiloxane network for fuel cell

The semi-interpenetrating polymer network (semi-IPN) based electrolyte membrane was synthesized from the poly(arylene ether ketone)-b-ketone sulfonated poly(arylene ether ketone) multi-block copolymer (PAEK-b-KSPAEK) and the organosiloxane organic-inorganic hybrid polymer network (OSPN) pre-synthesized. The chemical structure of the synthesized PAEK-b-KSPAEK and semi-IPN was identified using 1H and 19F nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, and the dimension of the phase separated ionic clusters was examined by small angle X-ray scattering spectroscopy. Introduction of OSPN to PAEK-b-KSPAEK improved not only the thermal and mechanical stability (toughness) but also the oxidative stability. The performance of the membrane electrode assembly fabricated with the semi-IPN electrolyte membranes was superior to that of the pure block copolymer membrane because of the enhanced proton conductivity and toughness. While the semi-IPN24 membrane showed the comparable proton conductivity and cell performance to Nafion 115 membrane, its methanol permeability was significantly lower than that of Nafion 115 membrane.

Pendant dual-sulfonated poly(arylene ether ketone) multi-block copolymer membranes for enhanced proton conductivity at reduced water swelling

The proton exchange membranes are synthesized from poly(arylene ether ketone) (PAEK) multi-block copolymers with and without sulfonated groups. The hydrophilic PAEK block is dual - sulfonated at the pendant site to enhance the proton conductivity of the membrane, while the hydrophobic block length is enlarged to reduce its swelling (increase dimensional stability) associated with water accommodation. The chemical structures of the synthesized oligomers and copolymers are identified using 1H and 19F NMR, ATR-FTIR, and GPC. The ion cluster dimension of the membrane is analyzed by SAXS. The effect of copolymer composition on the membrane properties is investigated measuring the proton conductivity, water uptake, swelling ratio, and cell performance along with the thermal, mechanical, and oxidative stability. The prepared membranes exhibit lower swelling ratio but higher proton conductivity than Nafion115 membrane. Specifically, B.PAEK25-SDPA shows superior cell performance to Nafion115.

Constructing Long-Range Transfer Pathways with Ordered Acid-Base Pairs for Highly Enhanced Proton Conduction.

Acid-base pairs hold great superiority in creating proton defects and facilitating proton transfer with less or no water. However, the existing acid-base complexes fail in assembling into ordered acid-base pairs and thus cannot always take full advantage of the acid-base synergetic effect. Herein, polymer quantum dots with inherent ordered acid-base pairs are utilized and anchored on dopamine-coated graphene oxide, thus forming into long-range conducting pathways. The resultant building blocks ( nPGO) are integrated in a sulfonated poly(ether ether ketone) matrix to fabricate composite membranes. The constructed long-range transfer highways with ordered acid-base pairs impart to the composite membrane significantly enhanced proton conduction ability. Under the hydrated state, the composite membrane attains 91% increase over the control membrane in conductivity, and the single-cell fuel based on the membrane achieves 71% promotion in maximum power density. Under anhydrous conditions, more striking augment in conduction is observed for the composite membrane, reaching 7.14 mS cm-1, almost 10 times of the control membrane value (0.78 mS cm-1). Remarkably, such anhydrous proton conduction performance is even comparable to that of the composite membrane impregnated with ionic liquids, which is hard to realize with conventional fillers. Collectively, these results endow composite membranes great potential for applications in hydrogen-based fuel cells, sensors, and catalysis.

Energy material - the role of silicotungstic acid and fly ash in sulfonated poly (ether sulfone) composites for PEMFC applications

The composite polymer electrolyte membranes were prepared from sulfonated poly (ether sulfone) (SPES), silicotungstic acid (STA) and fly ash (FA). Post sulfonation process was adopted to synthesize SPES using sulphuric and chlorosulfonic acid. The prepared electrolyte membranes were examined by water uptake capacity, swelling ratio, ion-exchange ability, proton conductivity, thermal stability and electrochemical performance for evaluating the pertinence of these membranes in fuel cell applications. As such the pristine membrane restricts with the proton conductivity of 0.042 S cm−1 at 30 °C and 0.060 S cm−1 at 90 °C while the polymer composite membrane, SP-STA-FA-10 reveals the maximum conductivity of 0.054 S cm−1 at 30 °C and 0.073 S cm−1 at 90 °C. It also exhibits good thermal stability than that of the pure membrane. The membrane electrode assemblies (MEAs) have been successfully developed from SPES as well as SP-STA-FA-10 membranes and their electrochemical performance were studied the wide range of current density. Herein, the composite membranes derived from SPES, STA and FA can be viable candidates for fuel cell applications.

Improving the redox flow battery performance of low-cost thin polyelectrolyte membranes by layer-by-Layer Surface assembly

The search of new membranes for vanadium redox flow battery with low vanadium ions permeation rates, high ion conductivity, excellent proton conductivity, low area resistance, chemical stability, and low cost is on a soaring demand. In this work, a simple modification method is applied to improve the performance of commercially available low-cost membranes by applying several polyelectrolytes layers. Particularly, graphene-containing commercial perfluorinated sulfonic acid membrane of GN212C with a thickness of 33 μm is modified by introducing alternate layers of positively charged poly(diallyldimethylammonium chloride) and negatively charged poly(sodium styrene sulfonate). Microscopy and spectroscopy investigations indicate that the polyelectrolytes layers are successfully deposited on the membrane surface. The effects of the layer composition and number of bilayers are evaluated with regard to vanadium ion permeability, proton conductivity and battery performance. The modified membranes exhibit an improved vanadium (VO2+) barrier property, which enhances the VRFB single cell performance in terms of coulombic efficiency and energy efficiency compared to pristine GN212C and Nafion 117 membranes. The overall results suggest that the bi-ionically modified membrane is a potential candidate for application in flow battery despite its small thickness.

Enhancement in proton conductivity and methanol resistance of Nafion membrane induced by blending sulfonated poly(arylene ether ketones) for direct methanol fuel cells

In the present work, three kinds of sulfonated poly(arylene ether ketones) (SPAEKs) with different structures are introduced into Nafion as blending modifiers to enhance the properties of Nafion, especially methanol resistance. Characterizations such as transmission electron microscope (TEM), proton conductivity, methanol crossover, and single cell performance, are carried out to evaluate these composite membranes (SPAEK@Nafion) as prepared. Besides, recast Nafion membrane is prepared and characterized for comparison via the same method. By investigating the microstructure of SPAEK@Nafion membranes, p-BPAF@Nafion membrane is found to have the most homogeneous distribution and Nafion-like phase separation among these membranes. The pendent sulfobutyl side-chain and fluorinated main chain of p-BPAF make it most similar structure with Nafion among three modifiers, and such Nafion-liked structure provides p-BPAF a good compatibility with Nafion, which can facilitate its enhancement for Nafion. Consequently, p-BPAF@Nafion-7.5 exhibits higher proton conductivity (0.256 S cm−1), lower methanol permeability (1.87 × 10−6 cm2 s−1), and better selectivity (13.69 × 104 S s cm−3) than those of recast Nafion. Therefore, owing to high proton conductivity and good methanol resistance, p-BPAF@Nafion-7.5 possesses a good DMFC performance with an open circuit voltage of 0.836 V and a peak power density of 111.53 mW cm−2, when fed with 2 M methanol at 80 °C.

Sulfonated poly(etheretherketone) based nanocomposite membranes containing POSS-SA for polymer electrolyte membrane fuel cells (PEMFC)

Nanocomposite membranes were prepared using sulfonated polyhedral oligomeric silsesquioxane (POSS-SA) and incorporated into sulfonated polyetheretherketone (sPEEK) for their use in polymer electrolyte membrane fuel cells. The POSS-SA concentration was varied to investigate its effect on the nanostructure morphology, mechanical properties, proton conductivities, and cell performance of nanocomposite membranes. POSS-SA served as a plasticizer: The plasticizer effect of POSS-SA affected the formation of broadened proton-conducting nanochannels and enhanced the tensile strain of nanocomposite membranes. Tensile strain and yield modulus increased by 66.7% and 63.6%, respectively. Acidic POSS-SA served as a proton donor to sPEEK and increased the sPEEK nanochannel dimensions by 23%, leading to enhanced proton conductivities and cell performance. The highest proton conductivity and cell performance was achieved using 1.5 wt% of POSS-SA; these values decreased with > 1.5 wt% of POSS-SA, caused by the blocking of the nanochannels by POSS-SA aggregates. Compared with those observed for pristine sPEEK, the highest proton conductivity and maximum current density were 0.097 S/cm and 0.97 A/cm2, which were increased by 38.6% and 76.3%, respectively. Electrochemical impedance spectroscopy revealed that the superior cell performance with 1.5 wt% of POSS-SA is strongly related to the decreased interfacial resistance caused by expanded hydrophilic domains.

Synthesis and conductive performance of quaternary heteropoly acid H5SiW9Mo2VO40⋅13H2O

A novel molybdenum- and vanadium-substituted quaternary heteropoly acid H5SiW9Mo2VO40[Formula: see text][Formula: see text][Formula: see text]13H2O has been synthesized and characterized by IR, UV, TG-DTA and XRD. The proton conductive performance was studied by the electrochemical impedance spectroscopy (EIS), which demonstrated that H5SiW9Mo2VO40[Formula: see text][Formula: see text][Formula: see text]13H2O shows excellent proton conduction performance with proton conductivity reaching [Formula: see text][Formula: see text]S[Formula: see text]cm[Formula: see text] at 60∘C and 80% relative humidity. In the temperature range of measurements, conductivity enhances with higher temperature. The proton conductive mechanism of this new heteropoly acid is the vehicle mechanism due to the activation energy of 31.91[Formula: see text]kJ [Formula: see text] mol[Formula: see text].

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.