Proton Conductivity Research Articles

Boosting the proton conductivity, chemical stability, and fuel cell performance of nafion membrane at high operating temperatures and low humidity levels by incorporating phytic acid

Nafion as a conducting polymer faces conduction challenges at high operating temperatures and low humidity levels, leading to an undesired fuel cell performance. Here, we offer a step forward towards the use of Nafion as a high-temperature/low-humidity membrane in fuel cells through the incorporation of phytic acid (IP6) by a doping process. The synergetic effect of IP6 on the physicochemical properties, mechanical characteristics, oxidative durability, proton conductivity, and fuel cell performance of Nafion membrane is studied. Compared to the pristine Nafion, the Nafion-IP6 membrane has shown a 3-fold increase in Young's modulus, a 83%-increase in water uptake, and around 6-fold increase in proton conductivity at 100 °C under 25% RH. The Ea has reached 8.3 kJ/mol, indicating a vehicular/Grotthuss proton conduction mechanism. The Nafion-IP6 based MEA has shown a 71%-increase in the output power density and a 54%-increase in the limiting current density compared to the pristine Nafion-based MEA.

Two-in-one: Proton-conductive and luminescence properties of one strontium(II)-organic framework bearing imidazole dicarboxylate

Despite the current surge in the production of metal-organic frameworks (MOFs) by crystal engineering, more structurally diverse MOFs must be developed and prepared for the study of their application properties and structural stability. Herein, one novel two-dimensional MOF, [Sr(μ5-p-FPhHIDC)(H2O)]n (1) was solvothermally constructed and structurally characterized by adopting an organic linker, 2-(4-fluorophenyl)-1H-imidazole-4,5-dicarboxylic acid (p-FPhH3IDC), in which the [SrO9] tetrakaidecahedrons were joined by the organic linkers to constitute a beautiful grid structure. The remarkable fluorescence characteristics and proton transfer are due to the strong coordination between the organic ligands and the central metal ions in the framework of 1, as well as the carboxylic acid and coordination water molecules carried on the framework. Extensive tests demonstrated that, at relative humidity of 75–98 %, this MOF displayed a specific proton conductivity (10−7-10−5 S/cm) and significant room-temperature solid-state fluorescence (λem = 406 nm). Proton conduction and luminescence mechanisms were also conjectured. This study is a helpful resource for creating MOF materials with a range of application-specific properties.

Wettability of sulfonated graphene oxide membranes for proton exchange membrane fuel cells

The self-assembling ability of graphene oxide (GO) and the possibility to obtain derivatives enriched with functional groups make it a suitable material for the production of thin membranes for many different applications. In particular, sulfonated graphene oxide (SGO) membranes can be promising electrolytes for proton exchange membrane fuel cells (PEMFCs), especially at high temperatures. The degree of sulfonation should improve the proton conductivity, but it should not reverse the mild hydrophilic behaviour that is among the requirements for a good performance. SGO membranes at six different sulfonation degrees were produced with an innovative procedure and characterized, together with a benchmark GO membrane, by means of scanning electron microscopy and X-ray diffraction analyses. Then, static and dynamic contact angles, spreading factors, and work of adhesion with water were measured and discussed in relation with the previous characterizations and with the water uptake and proton conductivity. The results show that the increase of the degree of sulfonation leads to a rise in the contact angles, as well as to a significant increase of the proton conductivity, but the hydrophilic behaviour is conserved except for the highest degree of the acid-to-GO ratio, at which in any case such effect may be only superficial.

An investigation into proton conduction of ga doped boehmite based memristor with simulated synaptic behavior

Artificial synapses based on protonic memristor have great potential in constructing neural morphological computing system. However, further investigation is still required to understand the proton conduction mechanism of protonic memristors. Here, we present a new type of Ga doped boehmite based memristors with artificial synapse functionality, which can achieve variations in conductance levels by precise control of the Ga doping content. Compared with undoped boehmite, there is no obvious change in crystal structure, particle morphology and chemical bond doped with different of concentration Ga. The change in the electrical conductance is found to be a result of proton transfer, closely resembling what takes place in biological neurons. Furthermore, the first-principle density functional theory (DFT) calculation is conducted to elucidate the proton conduction mechanism and zig-zag-like pathways for proton transfer in the memristor was proposed. The results establish a precedent for tuning the proton transfer behaviour in memristor-based neural devices, thereby enhancing their practicality. It provides a novel approach for studying the resistance switching behavior in proton transfer-based memristors.

Improving the ohmic polarization of high-temperature proton exchange membrane fuel cells using crosslinked polybenzimidazole membranes containing acidophilic quaternary ammonium groups synthesized by one-step strategy

Ingenious crosslinked network structure in phosphoric-acid-doped polybenzimidazole membranes can mitigate the mutual restriction of proton conductivity and mechanical properties. However, the complicated synthesis of tailored macromolecular crosslinker and the time-consuming post-treatment hinder their practical application as high-temperature proton exchange membranes. Herein, crosslinked polybenzimidazole membranes are synthesized using small molecular crosslinkers containing acidophilic quaternary ammonium groups through a one-step crosslinking strategy. After doping with phosphoric acid, the quaternary ammonium-biphosphate ion-pair coordination and the crosslinked structure result in the improved anhydrous proton conductivity, oxidation stability, and mechanical strength of the formed membranes compared to the sample without the crosslinking structure. A membrane with the optimized degree of crosslinking exhibits an anhydrous conductivity of 72.27 mS/cm at 160 °C, with a tensile strength of 12.14 MPa. Benefiting from the crosslinked structure and high proton conductivity, the accordingly formed membrane electrode assembly possesses a high open-circuit voltage of 1.01 V and animproved ohmic polarization, delivering a peak power density of 0.66 W/cm2 using hydrogen as fuel and air as oxidant.

Effect of Plasma pretreatment and Graphene oxide ratios on the transport properties of PVA/PVP membranes for fuel cells

In this study, a novel proton-conducting polymer electrolyte membrane based on a mixture of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) (1:1) mixed with different ratios of graphene oxide (GO) and plasma-treated was successfully synthesized. Dielectric barrier dielectric (DBD) plasma was used to treat the prepared samples at various dose rates (2, 4, 6, 7, 8, and 9 min) and at fixed power input (2 kV, 50 kHz). The treated samples (PVA/PVP:GO wt%) were soaked in a solution of styrene and tetrahydrofuran (70:30 wt%) with 5 × 10−3 g of benzoyl peroxide as an initiator in an oven at 60 °C for 12 h and then sulfonated to create protonic membranes (PVA/PVP-g-PSSA:GO). The impacts of graphene oxide (GO) on the physical, chemical, and electrochemical properties of plasma-treated PVA/PVP-g-PSSA:x wt% GO membranes (x = 0, 0.1, 0.2, and 0.3) were investigated using different techniques. SEM results showed a better dispersion of nanocomposite-prepared membranes; whereas the AFM results showed an increase in total roughness with increasing the content of GO. FTIR spectra provide more information about the structural variation arising from the grafting and sulfonation processes to confirm their occurrence. The X-ray diffraction pattern showed that the PVA/PVP-g-PSSA:x wt% GO composite is semi-crystalline. As the level of GO mixing rises, the crystallinity of the mixes decreases. According to the TGA curve, the PVA/PVP-g-PSSA:x wt% GO membranes are chemically stable up to 180 °C which is suitable for proton exchange membrane fuel cells. Water uptake (WU) was also measured and found to decrease from 87.6 to 63.3% at equilibrium with increasing GO content. Ion exchange capacity (IEC) was calculated, and the maximum IEC value was 1.91 meq/g for the PVA/PVP-g-PSSA: 0.3 wt% GO composite membrane. At room temperature, the maximum proton conductivity was 98.9 mS/cm for PVA/PVP-g-PSSA: 0.3 wt% GO membrane. In addition, the same sample recorded a methanol permeability of 1.03 × 10−7 cm2/s, which is much less than that of Nafion NR-212 (1.63 × 10−6 cm2/s). These results imply potential applications for modified polyelectrolytic membranes in fuel cell technology.

Dielectric characterisation of chitosan-based composite membranes containing fractionated kraft and organosolv lignin

Chitosan-based composite membranes with fractionated kraft and organosolv lignin were prepared by solvent casting. A small lignin fraction (1%) was added to the neat chitosan to obtain a good distribution. The influence of lignin extraction with ethyl acetate and consequently ethanol on the dielectric and conductive properties of the composites was investigated by dielectric thermal analysis (DETA). Overall, the chitosan-lignin composites exhibit three relaxation mechanisms (β, βwet, and α) and two conductivity phenomena (σ and MWS). FTIR analysis showed that the composites with organosolv lignin fractions have fewer hydroxyl groups than those with kraft lignin, which decreases slightly further for both after ethanol extraction. The lignin fractions with lower molecular weight and higher OH content show stronger interactions with chitosan, due to hydrogen bonding. These interactions affect the thermal activation and cooperativity of the β-, βwet, and α-relaxation. Furthermore, the kraft lignin fractions with many polar groups are very compatible with the chitosan matrix, resulting in a more compact structure and higher fragility. The membranes CS OLEA and CS KLE have a lower electron conductivity and a higher proton conductivity. Thus, they have promising conductivity properties for fuel cell applications.

Electrochemical power generation humidity sensor based on WS2 nanoflakes

The electrochemical power generation humidity sensor has received widespread attention due to its zero-power consumption. In this work, we propose an electrochemical power generation humidity sensor using WS2 nanoflakes as the humidity sensing material, without adding additional alkali metal salts (such as LiCl and NaCl) or other added materials or functional group treatments. The results show that the humidity sensor exhibits wide humidity detection range (18.7%−91.5% relative humidity (RH)), fast response/recovery speeds (8.4/5.2 s), good repeatability (20 cycles) and small humidity hysteresis (∼3.4% RH) at room temperature of 25 °C. The output voltage of the humidity sensor is 0.47 V at 91.5% RH. Combined with good water molecule adsorption and proton conductivity of the WS2 nanoflakes, the humidity sensing and power generation mechanism of the WS2 electrochemical power generation humidity sensor can be explained by the redox reactions occurring at the positive and negative electrodes (Cu and Al). Finally, we demonstrate the application of the humidity sensor in respiratory detection. This work provides a useful approach for fabricating electrochemical power generation humidity sensor with a simple single humidity sensing material.

Grafting of Amine End-Functionalized Side-Chain Polybenzimidazole Acid-Base Membrane with Enhanced Phosphoric Acid Retention Ability for High-Temperature Proton Exchange Membrane Fuel Cells.

A high phosphoric acid uptake and retention capacity are crucial for the high performance and stable operation of phosphoric acid/polybenzimidazole (PA/PBI)-based high-temperature proton exchange membranes. In this work, amine end-functionalized side-chain grafted PBI (AGPBI) with different grafting degrees are synthesized to enhance both the phosphoric acid uptake and the acid retention ability of the accordingly formed membranes. The optimized acid-base membrane exhibits a PA uptake of 374.4% and an anhydrous proton conductivity of 0.067 S cm-1 at 160 °C, with the remaining proton conductivity percentages of 91.0% after a 100 h stability test. The accordingly fabricated membrane electrode assembly deliver peak power densities of 0.407 and 0.638 W cm-2 under backpressure of 0 and 200 kPa, which are significantly higher than 0.305 and 0.477 W cm-2 for the phosphoric acid-doped unmodified PBI membrane under the same conditions.

PTFE-reinforced pore-filling proton exchange membranes with sulfonated poly(ether ether ketone)s and poly(aryl ether sulfone)s

It is a technical challenge to improve the dimensional and chemical stability of pore-filling proton exchange membranes (PEMs) filled with high-sulfonated poly(ether ether ketone) (SPEEK) electrolytes. To solve this issue, double-electrolyte pore-filling PTFE PEMs were prepared by co-filling sulfonated poly(aryl ether sulfone) (SPAES) and SPEEK in this work. Utilizing ethanol hydrophilic pre-treatment, the double-electrolyte can be efficiently and uniformly infused into the porous PTFE, resulting in a compact, homogeneous and defect-free membrane. The existence of low-sulfonated SPAES40 in the double-electrolyte demonstrates a quite positive effect on inhibiting the dissolution of high-sulfonated SPEEK70 at high temperatures and controlling membrane swelling. Consequently, the PTFE/SPEEK-SPAES membrane shows 103.4 % higher proton conductivity, 33.6 % and 21.5 % lower in-plane and through-plane swelling than the control PTFE/SPEEK70 membrane at 90 °C. Moreover, heat treatment further enhances the mechanical and antioxidant characteristics of the membrane by forming –SO2- crosslinking. The resulting thermally cross-linked membrane exhibits 76.5 % lower oxidation mass loss, 70.4 % and 38.2 % higher elongation at break and tensile stress than the control PTFE/SPEEK70 membrane. After 48 h fuel cell operation, the output voltage of the PTFE/SPEEK-SPAES(1:1)* membrane only decreases by 3.6 %, which is better than the control PTFE/SPEEK70 membrane (46.2 %). This proves that a double-electrolyte pore-filling membrane is an efficient and facile method to strengthen the stability of PEMs.

Magnetically aligned composite membranes based on sulfonated poly(ether ether ketone) and phosphotungstic acid-loaded magnetic nanoparticles for fuel cell

In this work, phosphotungstic acid (HPW)-loaded polydopamine-coated magnetic nanoparticles (DMNPs@HPW) were prepared and incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix with magnetic field assistance to construct aligned channels to shorten proton transport pathways. The structure of the prepared composite membranes (M-SP/DMNPs@HPW) with magnetic field-induced proton channels was confirmed by SEM. The proton conductivity of M-SP/DMNPs@HPW-2 was significantly improved, with in-plane proton conductivity (σ//) of 159.3 mS/cm and through-plane proton conductivity (σ⊥) of 129.2 mS/cm in the hydrated state at 80 °C, which were 1.31 and 1.57 times higher than the pristine SPEEK membrane, due to the strong acidity of HPW and acid-base interaction of amine and sulfonic acid groups. Meanwhile, the σ⊥ of M-SP/DMNPs@HPW-2 was 1.14 times higher than that of SP/DMNPs@HPW-2 membrane prepared without magnetic field assistance. The fuel cell power output of M-SP/DMNPs@HPW-2 was 433 mW/cm2, while SP/DMNPs@HPW-2 and pristine SPEEK membranes tested under the same conditions were 360 mW/cm2 and 277 mW/cm2, respectively. The hydrogen crossover of M-SP/DMNPs@HPW-2 was slightly increased compared to SP/DMNPs@HPW-2 due to the construction of through-plane proton transport channels in the membrane.

A biostimulant prepared from red seaweed Kappaphycus alvarezii induces flowering and improves the growth of Pisum sativum grown under optimum and nitrogen-limited conditions.

Nitrogen (N) is one of the critical elements required by plants and is therefore one of the important limiting factors for growth and yield. To increase agricultural productivity, farmers are using excessive N fertilizers to the soil, which poses a threat to the ecosystem, as most of the applied nitrogen fertilizer is not taken up by crops, and runoff to aquatic bodies and the environment causes eutrophication, pollution, and greenhouse gas emissions. In this study, we used LBS6, a Kappaphycus alvarezii-based biostimulant as a sustainable alternative to improve the growth of plants under different NO3 - fertigation. A root drench treatment of 1 ml/L LBS6 significantly improved the growth of Pisum sativum plants grown under optimum and deficient N conditions. No significant difference was observed in the growth of LBS6-treated plants grown with excessive N. The application of LBS6 induced flowering under optimum and deficient N conditions. The total nitrogen, nitrate and ammonia contents of tissues were found to be higher in treated plants grown under N deficient conditions. The LBS6 treatments had significantly higher chlorophyll content in those plants grown under N-deficient conditions. The root drench application of LBS6 also regulated photosynthetic efficiency by modulating electron and proton transport-related processes of leaves in the light-adapted state. The rate of linear electron flux, proton conductivity and steady-state proton flux across the thylakoid membrane were found to be higher in LBS6-treated plants. Additionally, LBS6 also reduced nitrogen starvation-induced, reactive oxygen species accumulation by reduction in lipid peroxidation in treated plants. Gene expression analysis showed differential regulation of expression of those genes involved in N uptake, transport, assimilation, and remobilization in LBS6-treated plants. Taken together, LBS6 improved growth of those treated plants under optimum and nitrogen-limited condition by positively modulating their biochemical, molecular, and physiological processes.

Impact of SiO2 Modification on the Performance of Nafion Composite Membrane

Using Nafion212 membrane and TEOS solution as raw materials, Nafion212/SiO2 composite membranes were prepared. In the in situ sol-gel reaction process, a series of Nafion/SiO2 composite membranes were prepared by varying the reaction temperature and reaction time. The effects of different modification schemes on Nafion/SiO2 composite membranes were studied using SEM, EDS, TEM, TGA, XRD, and mechanical tensile experiments, among other methods. The results show that Nafion/SiO2 composite membranes prepared at 3°C exhibit a well-separated phase structure and excellent water retention properties, with a water uptake of 29.23% and a swelling ratio of 24.25%. These membranes also demonstrate outstanding physical and chemical performance, with a maximum tensile stress of 13.6 MPa and an elongation at a break of 270%. At 110°C, the proton conductivity of the Nafion/SiO2 composite membrane reaches 0.172 S/cm, meeting the requirements for high-temperature proton exchange membrane fuel cells.

Silane-crosslinked polybenzimidazole with different hydroxyl content for high-temperature proton exchange membrane

High temperature proton exchange membrane fuel cells (HT-PEMFCs) can operate over 100 °C without humidification, which avoids the catalyst poisoning and enhances the efficiency of the power conversion. However, the classic phosphoric acid (PA) doped polybenzimidazole (PBI) still remains the challenge in the trade-off between mechanical strength and proton conductivity. The γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560), as a crosslinking agent, is widely used to improve the mechanical properties of membranes. Although it can enhance the mechanical strength of PBI membranes, it sacrifices the hydrogen of imidazole groups, resulting in a decrease in proton conductivity. In this present work, silane-crosslinked PBI proton exchange membranes (PEMs) were synthesized by the reaction between the pyridine-bridged PBI containing different hydroxyl (-OH) content with KH560. Through comprehensive structural characterization of the polymer and model compound, it has been determined that this crosslinking method does not compromise the N–H acidic sites on the imidazole ring. The crosslinking agent KH560 provides additional hydroxyl groups to PBI and participates in the construction of hydrogen bonding networks after the ring-opening reaction. It was found that the addition of pyridine and hydroxyl groups could promote the phosphoric acid uptake, and the appropriate degree of silane crosslinking could maintain the PBI membranes with reasonable mechanical properties. Proton conductivity and HT-PEMFCs performance of the obtained crosslinked films were further enhanced with the dimensional stability, thermal stability and mechanical properties. Among them, CPyOPBI–OH–20 presented the best overall performance, exhibiting the highest proton conductivity of 0.095 S cm−1 and the maximum power density of 767 mW cm−2 at 180 °C under the anhydrous condition, which was 4.2 times that of OPBI (182 mW cm−2).

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.

Electrospinning-assisted construction of rapid proton conduction channels in halloysite nanotube-encapsulated ionic liquid-embedded sulfonated poly(ether ether ketone) proton exchange membranes

The most fatal drawback of traditional sulfonated polymer proton-exchange membranes (PEMs) is their heavy dependence on water molecules to conduct protons, which causes a sharp decrease in their proton conductivity in low-humidity environments. Here, composite membranes were fabricated by electrostatically spinning halloysite nanotube-encapsulated ionic-liquids (IL@HNTs) incorporated into sulfonated poly(ether ether ketone) (SPEEK) (SPEEK/IL@HNTs). Using electrospinning, one-dimensional IL@HNTs ionogels with good water absorption were axially and uniformly aligned along the fiber filament direction. This formed long-range uninterrupted proton conduction pathways that greatly improved the proton conductivity of the composite membrane under various humidity environments. The axially-aligned structure facilitated crystallization, which improved the mechanical properties and thermal stability of the composite membrane. The SPEEK/6IL@HNTs membrane exhibited a through-plane proton conductivity of 139.2 mS cm−1 at 90 °C/98 % RH, representing a significant increase compared with the intrinsic SPEEK membrane. The SPEEK/6IL@HNTs membrane demonstrated a maximum power density of 732 mW cm−2, which exceeded that of the Nafion115 membrane (328 mW cm−2) by a factor of 2.2. It exhibited a single-cell performance equivalent to that of the Nafion212 membrane (723 mW cm−2), demonstrating that this provides a feasible approach to operating fuel cells in low-humidity environments without additional humidification.

Improving the proton conductivity of MOF materials by regulating the pore space

The construction of metal-organic frameworks (MOFs) with structural tunability, designability, and high stability is crucial in proton conduction studies. In this paper, MOF-801 and UiO-66 were used as precursors. A solvothermal synthesis method was employed to modulate the pore space of composite MOFs. The hydrogen-bonding network and structure within the pore cavities are adjusted by varying the molar ratios of fumaric acid and terephthalic acid to improve the proton transfer rate and proton conductivity of the materials. A total of 14 materials, MOF/MOG-801&UiO-66-X (X is the molar ratio of fumaric acid and terephthalic acid) were synthesised, the variation of proton conductivity with temperature of which was investigated at different tempertures and humidities. The results shows that MOG-801&UiO-66–1:1 has the best proton conductivity with 0.12 S cm−1 at 353 K and 100 % RH, which is 5 times higher than that of MOF-801&UiO-66–1:3 (2.54 × 10−2 S cm−1), 11 times higher than that of MOF-801 and 22 times higher than that of UiO-66. Based on the calculated activation energy and structural characterisation, the proton conduction mechanism of the composite was investigated. This work opens up novel research fields for the design of new proton-conducting MOF materials.

A highly-selective layer-by-layer membrane modified with polyethylenimine and graphene oxide for vanadium redox flow battery

ABSTRACT A selective composite membrane for vanadium redox flow battery (VRFB) was successfully prepared by layer-by-layer (LbL) technique using a perfluorosulfonic sulfonic acid or Nafion 117 (N117). The composite membrane referred as N117-(PEI/GO)n, was obtained by depositing alternating layers of positively charged polyethylenimine (PEI) and negatively charged graphene oxide (GO) as polyelectrolytes. The physicochemical properties and performance of the pristine and composite membranes were investigated. The membrane showed an enhancement in proton conductivity and simultaneously exhibited a notable 90% reduction in vanadium permeability. This, in turn, results in a well-balanced ratio of proton conductivity to vanadium permeability, leading to high selectivity. The highest selectivity of the LbL membranes was found to be 19.2 × 104 S.min/cm3, which is 13 times higher than the N117 membrane (n = 0). This was translated into an improvement in the battery performance, with the n = 1 membrane showing a 4–6% improvement in coulombic efficiency and a 7–15% improvement in voltage efficiency at current densities ranging from 40 to 80 mA/cm2. Furthermore, the membrane displays stable operation over a long-term stability at around 88% at a current density of 40 mA/cm2, making it an attractive option for VRFB applications using the LbL technique. The use of PEI/GO bilayers maintains high proton conductivity and VE of the battery, opening up possibilities for further optimization and improvement of VRFBs.

Random sulfonated poly(arylene ether sulfone) and sulfonated poly(arylene ether ketone) membranes for fuel cell applications

AbstractIn this study, sulfonated poly(arylene ether sulfone) (SPAES) and sulfonated poly(arylene ether ketone) (SPAEK) were randomly synthesized, employing a presulfonation process. This presulfonation process resulted in a more controlled and reproducible sulfonation level. The respective polymers were prepared using 2,2‐Bis(4‐hydroxyphenyl) propane at 50% molar ratio, which also provided some membrane elasticity. The resulting polymers, each had 25% of the block containing the sulfonic domains (SPAES A 25 and SPAEK A 25). Better conductive membranes were achieved for the random sulfone polymers than for the random ketone polymers, with values, respectively, of 0.24 and 0.07 S cm−1 at 80°C. The lower proton conductivity from the ketone‐based polymer was compensated with very low methanol permeability (0.25 × 10−6 cm2 s−1) and outstanding oxidative stability. The selectivity of both polymer membranes exceeded the reported values for the state‐of‐the‐art Nafion® 117 and other commercially available options. Both polymer membranes, with their unique combination of ionic domains, elastomeric blocks, and resulting morphology, could be viable candidates for fuel cell applications.

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.