Facile self-crosslinking to improve mechanical and durability of polynorbornene for alkaline anion exchange membranes

Crosslinking is a valid approach to enhance the mechanical and durability performance of anion exchange membranes (AEMs). Herein, a facile and effective self-crosslinking strategy, with no need for an additional crosslinker or a catalyzer, is proposed. A series of tunable self-crosslinking and ion conduction polynorbornene membranes are designed. The 5-norbornene-2-methylene glycidyl ether (NB-MGE) component which affords self-crosslinking enhances dimensional stability, while the flexible 5-norbornene-2-alkoxy-1-hexyl-3-methyl imidazolium chloride (NB-O-Im⁺Cl⁻) hydrophilic unit contributes high conductivity. The crosslinking significantly decreases the water uptake, and water swelling ratio provides excellent solvent-resistance and enhances the thermal and mechanical properties. Additionally, crosslinked rPNB-O-Im-x AEMs exhibit desirable alkaline stability. Impressively, the rPNB-O-Im-30 (IEC = 1.377) shows a moderate ion conductivity (61.8 m S cm⁻¹, 80 °C), with a suppressed water absorption and 88.17% initial OH⁻ conductivity is maintained after treated for 240 h with a 1.0 M NaOH solution at 60 °C. Suitably assessed of rPNB-O-Im-30 AEM reveals a 98.4 mW cm⁻² peak power density reached at a current density of about 208 mA cm⁻². The report offers a facile and effectual preparative technique for preparing dimensional and alkaline stable AEMs for fuel cells applications.     

A novel quaternized poly(ether sulfone) membrane for alkaline fuel cell application

A new type of poly(ether sulfone)‐based self‐aggregated anion exchange membrane (AEM) was successfully synthesized and used in H₂/O₂ fuel cell applications. The self‐aggregated structural design improves the effective mobility of OH^? ion and increases the ionic conductivity of AEM. Proton nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra confirm successful chloromethylation and quaternization in the poly(ether sulfone). Thermogravimetric analysis curves show the self‐aggregated membrane was thermally stable up to 180 °C. The AEM also has excellent mechanical properties, with tensile strength 53.5 MPa and elongation at break 47.6% under wet condition at room temperature. The performance of H₂/O₂ single fuel cell at 30 °C showed the maximum power density of 162 mW cm^?2. These results show that the self‐aggregated quaternized poly(ether sulfone) membrane is a potential candidate for alkaline fuel cell applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and characterization of organic-inorganic hybrid anion exchange membrane based on crown ether functionalized mesoporous SBA-NH2

In this paper, self-made diformyl-dibenzo-18-crown-6 ether (DDB₁₈C₆) is in-situ grafted into the pores of mesoporous molecular sieve (SBA-NH₂), and then the aforementioned modified molecular sieve (SBA-C) is introduced into the polyvinyl alcohol solution, and then the glutaraldehyde as the crosslinking agent to synthesized the anion exchange membrane under for fuel cell application. During the experiment, a series of anion exchange membranes (P-(SBA_x%-C), x is the mass fraction of SBA-NH₂) is developed and the pore channels and chemical structures of the aforementioned membrane is verified by FT-IR, SAXD, N₂ adsorption-desorption, ¹H NMR and XPS. Moreover, the performance of the membrane synthesized in this paper is also investigated and the results revealed that the unique membrane internal structure can improve the OH^? transportation efficiency. Furthermore, the ionic conductivity of P-(SBA_10%-C) membrane is the highest (0.107S·cm^?1) and the power density is the highest (354.8 mW cm^?2) at 80 °C. By immersing P-(SBA_10%-C) membrane in 6 mol L^?1 KOH solution for 168 h, the conductivity at 80 °C only decreased by 2%, proving that P-(SBA_10%-C) has a higher conductivity, good single cell performance and alkali stability.     

Block copolymer anion exchange membrane containing polymer of intrinsic microporosity for fuel cell application

High hydroxide conductivity and good stability of anion exchange membranes (AEMs) is the guarantee that anion exchange membrane fuel cells (AEMFCs) yield high power output for a long time. Balanced conductivity and stability can be better guaranteed by adopting a relatively low ion exchange capacity (IEC) while reducing the ion transport resistance Herein, a novel block copolymer AEM was designed and synthesized, which contains hydrophobic polymer of intrinsic microporosity (PIM) blocks and hydrophilic, quaternized polysulfone (PSF) blocks. The PIM block imparts high free volume to the membrane so that the resistance of hydroxide ion transport can be reduced; meanwhile, the hydrophilic block can self-assemble more easily to produce a better developed hydrophilic microphase, which may function as efficient channels for hydroxide ion transport. Both transmission electron microscopy images and small-angle X-ray scattering patterns suggested that the resulting AEM possessed a microphase separated morphology. The membrane showed a conductivity of 52.6 mS cm^-l at 80 °C with a relatively low IEC of 0.91 mmol g^?1. It also exhibited a good dimensional stability, swelling ratio maintained almost constant (ca. 17%) at 25 to 80 °C. The assembled H₂/O₂ fuel cell yielded a peak power density of 270 mW cm^?2 at 560 mA cm^?2. Our work demonstrates that incorporation of PIM in an AEM by means of block polymerization is an efficient way of promoting microphase separation and facilitating ion transport.     

Branched poly(ether ether ketone) based anion exchange membrane for H2/O2 fuel cell

High-performance anion exchange membranes (AEMs) are in need for practical application of AEM fuel cells. Novel branched poly(ether ether ketone) (BPEEK) based AEMs were prepared by the copolymerization of phloroglucinol, methylhydroquinone and 4,4′-difluorobenzophenone and following functionalization. The effects of the branched polymer structures and functional groups on the membrane's properties were investigated. The swelling ratios of all the membranes were kept below 15% at room temperature and had good dimensional stability at elevated temperatures. The branching degree has almost no effect on the dimensional change, but plays a great role in tuning the nanophase separation structure. The cyclic ammonium functionalized membrane showed a lower conductivity but a much better stability than imidazolium one. The BPEEK-3-Pip-53 membrane with the branching degree of 3% and piperidine functionalization degree of 53% showed the best performances. The ionic conductivity was 43 mS cm⁻¹ at 60 °C. The ionic conductivity in 1 M KOH at 60 °C after 336 h was 75% of its initial value (25% loss of conductivity), and the IEC was 83% of its initial value (17% loss of IEC), suggesting good alkaline stability. The peak energy density (60 °C) of the single H₂/O₂ fuel cell with BPEEK-3-Pip-53 membrane reached 133 mW cm⁻² at 260 mA cm⁻².     

Crosslinked anion exchange membranes with regional intensive ion clusters prepared from quaternized branched polyethyleneimine/quaternized polysulfone

A series of anion exchange membranes (AEMs) with regionally dense ion clusters are prepared by crosslinking quaternized polysulfone (QPSU) with quaternized branched polyethyleneimine (QBPEI). For the as-prepared QPSU/QBPEI AEMs, the hydrophilic QBPEI forms locally aggregated ion clusters in the QPSU matrix, which can promote the formation of an obvious microphase separation structure in the membrane. The QPSU/QBPEI-3 AEM with an ion exchange capacity of 1.88 meq/g exhibits the best performance, achieving a reasonably high ionic conductivity of 66.14 mS/cm at 80 °C and showing good oxidation stability and alkali resistance. Finally, the maximum power density of a single H₂/O₂ fuel cell with QPSU/QBPEI-3 AEM reaches 75.34 mW/cm² at 80 °C. The above results indicate that QBPEI with a dendritic structure and abundant anionic conductive groups has a good application prospect in the preparation of AEMs with locally aggregated ion clusters and microphase separation structures.     

Anion exchange membranes based on poly (ether ether ketone) containing N-spirocyclic quaternary ammonium cations in phenyl side chain

It was reported that the existence of N-spirocyclic quaternary ammonium (QA) cation could improve alkaline stability of anion exchange membrane materials (AEM). Therefore, the cyclo-quaternization reaction with pyrrolidine (Pyr) and piperidine (Pip) was carried out to prepare quaternized poly (ether ether ketone)s bearing five-membered and six-membered N-spirocyclic quaternary ammonium (QA) groups in the phenyl side chains (QPEEK-spiro-pyr and QPEEK-spiro-pip), respectively. From the transmission electron microscope, the hydrophilic-hydrophobic phase-separated morphology was formed in QPEEK-spiro membranes after incorporating N-spirocyclic QA cations and bulky spacer simultaneously in the phenyl side chain. The effect of N-spirocyclic QA groups on performance of resulted AEMs was then studied in detail. The anion conductivities of QPEEK-spiro-pyr and QPEEK-spiro-pip in OH^? form at 80 °C were 49.6 and 30.9 S cm^?1, respectively. The remaining proportions of hydroxide conductivity for QPEEK-spiro-pyr and QPEEK-spiro-pip membranes after immersing in 1 M NaOH at 60 °C were 81.0% and 74.7%, respectively, which were higher than that of 62.3% for QPEEK-TMA containing conventional QA groups in the phenyl side chain. Fuel cell assembled with QPEEK-spiro-pyr achieves a peak power density of 90 mW cm^?2. These results indicate the strategy of simultaneously introducing N-spirocyclic QA cations and bulky spacers can improve the performance of AEM to a certain extent. There are some other factors that influence the alkaline stability of the prepared AEMs, such as the existence of ether bonds in the main chain. However, this work still provides a valuable reference towards the molecular design of AEMs with improved performance.     

Preparation and characterization of a polyvinyl alcohol grafted bis-crown ether anion exchange membrane with high conductivity and strong alkali stability

A new type of symmetrical bis-crown ether is prepared by connecting dibenzo-18-crown-6 ether on both sides of the chromotropic acid, and then grafting the aforementioned bis-crown ether onto polyvinyl alcohol matrix to prepare a series of anion exchange membranes (AEMs), which their have high conductivity and strong alkali stability. These synthesized membranes were named B-C_X%-P AEMs (x is the mass percentage of the symmetrical bis-crown ether (B–C)). Then, the chemical structure of aforementioned AEMs were verified by means of ¹H NMR, FT-IR and UV. Meanwhile, the OH⁻ conductivity, alkaline stability and single cell performance of the synthesized membrane were also investigated. The results revealed that the conductivity of B–C_30%-P membrane is the highest at 80 °C (235 mS cm⁻¹), and the power density is also the highest (197 mW cm⁻²), and the alkali stability of the membrane synthesized in this paper was also improved. The conductivity at 80 °C was only reduced by 4%, which was obtained by immersing the B–C_30%-P membrane immersed in 6 mol L⁻¹ KOH solution for 168 h, which the aforementioned results proved that the synthesized membrane in this research had excellent OH⁻ conductivity and alkaline stability.     

Novel self-cross-linked multi-imidazolium cations long flexible side chains triblock copolymer anion exchange membrane based on ROMP-type polybenzonorbornadiene

A novel benzonorbornadiene derivative (BenzoNBD-Bis(Im⁺Br⁻-Im⁺I⁻)) grafted by multi-imidazolium cations side-chains combined the rigid alkyl spacer and flexible alkoxy spacer is designed and synthesized. Then, the BenzoNBD-Bis(Im⁺Br⁻-Im⁺I⁻) monomer is copolymerized with the epoxy functionalized norbornene monomer (NB-MGE) and norbornene (NB) via ring-opening metathesis polymerization (ROMP) using Grubbs 3rd catalyst. All as-designed triblock copolymer membranes (TBCMs) show a thermal decomposition temperature beyond 310 °C and can well be dissolved in common organic solvents. The self-cross-linked structure of anion exchange membrane (AEM) is confirmed by gel fraction and tensile measurement. The water uptake and swelling ratio of TBCMs and AEMs are also measured. Major properties required for AEMs such as ion exchange capacity (IEC), hydroxide conductivity and alkaline stability are investigated. AEM-9.09 shows a hydroxide conductivity of 100.74 mS cm⁻¹ at 80 °C. Besides, the micro-phase separated morphology of AEM is confirmed by TEM, AFM and SAXS analyses, AEMs formed distinct micro-phase separation. The as-prepared AEM exhibits a peak power density of 174.5 mW cm⁻² at 365.1 mA cm⁻² tested in a H₂/O₂ single-cell anion exchange membrane fuel cell (AEMFC) at 60 °C. The newly developed strategy of self-cross-linked multi-imidazolium cations long side-chains triblock benzonorbornadiene copolymer provides an effective method to develop high-performance AEMs.     

A facile method to synthesize BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) nanopowders for the application on highly conductive proton-conducting electrolytes

BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb), one kind of promising electrolyte materials for proton-conducting solid oxide fuel cells (H⁺-SOFCs), generally suffers from the poor sinterability, leading to poor electrochemical performances lower than expected. Herein, a facile method, modified room temperature solid-state reaction (M-RTSSR) was proposed for synthesizing highly active BZCYYb nanopowders. Pure perovskite BZCYYb powders can be obtained at a low calcination temperature of 950 °C and a short dwelling time of 3 h. The highly active character allows the sintering temperature of BZCYYb electrolytes decrease from 1550 °C to 1450 °C, thus effectively suppressing the Ba evaporation and promoting the grain growth. The electrical conductivity measured at 700 °C in wet air is 2.6 × 10^?2 S cm^?1, which mainly benefits from the improvement of grain boundary conductivity. According to the analysis based on space charge layers, the enhanced electrical performance can be ascribed to their lower space charge potential (Δφ (0)) and higher impurity blocking item (ω/d_g). Finally, the anode-supported single cell with such BZCYYb electrolytes reaches a peak power density of 0.54 W cm^?2 at 700 °C while taking humid H₂ (～3 vol% H₂O) as fuels and ambient air as oxidants.     

A facile,effective thermal crosslinking to balance stability and proton conduction for proton exchange membranes based on blend sulfonated poly(ether ether ketone)/sulfonated poly(arylene ether sulfone)

The development of hydrocarbon polymer electrolyte membranes with high proton conductivities and good stability as alternatives to perfluorosulfonic acid membranes is an ongoing research effort. A facile and effective thermal crosslinking method was carried out on the blended sulfonated poly (ether ether ketone)/poly (aryl ether sulfone) (SPEEK/SPAES) system. Two SPEEK polymers with ion exchange capacities (IECs) of 1.6 and 2.0 mmol g^?1 and one SPAES polymer (2.0 mmol g^?1) were selected to create different blends. The effect of thermal crosslinking on the fundamental properties of the membranes, especially their physicochemical stability and electrochemical performance, were investigated in detail. The homogeneous and flexible thermally-crosslinked SPEEK/SPAES membranes displayed excellent mechanical toughness (27–46 Mpa), suitable water uptake (<60%), high dimensional stability (swelling ratio < 15%) and large proton conductivity (>120 mS cm^?1) at 80 °C. The thermal crosslinking membranes also show significantly enhanced hydrolytic (<2.5%) and oxidative stability (<2%). Fuel cell with t-SPEEK/SPAES (1:2:2) membrane achieves a power density of 665 mW cm^?2 at 80 °C.     

High‐performance solid PEO/PPC/LLTO‐nanowires polymer composite electrolyte for solid‐state lithium battery

Solid polymer composite electrolyte (SPCE) with good safety, easy processability, and high ionic conductivity was a promising solution to achieve the development of advanced solid‐state lithium battery. Herein, through electrospinning and subsequent calcination, the Li_0.33La_0.557TiO₃ nanowires (LLTO‐NWs) with high ionic conductivity were synthesized. They were utilized to prepare polymer composite electrolytes which were composed of poly (ethylene oxide) (PEO), poly (propylene carbonate) (PPC), lithium bis (fluorosulfonyl)imide (LiTFSI), and LLTO‐NWs. Their structures, thermal properties, ionic conductivities, ion transference number, electrochemical stability window, as well as their compatibility with lithium metal, were studied. The results displayed that the maximum ionic conductivities of SPCE containing 8 wt.% LLTO‐NWs were 5.66 × 10^?5 S cm^?1 and 4.72 × 10^?4 S cm^?1 at room temperature and 60°C, respectively. The solid‐state LiFePO₄/Li cells assembled with this novel SPCE exhibited an initial reversible discharge capacity of 135 mAh g^?1 and good cycling stability at a charge/discharge current density of 0.5 C at 60°C.     

Highly alkaline stable fully-interpenetrating network poly(styrene-co-4-vinyl pyridine)/polyquaternium-10 anion exchange membrane without aryl ether linkages

To avoid the detrimental effect of aryl ethers on the alkali stability of anion exchange membrane (AEM), elaborately designed and synthesized poly(styrene-co-4-vinyl pyridine) (PS4VP) copolymer without aryl ether linkages is used to prepare AEMs. By introducing commercialized polyquaternium-10 (PQ-10) as the main ion-conducting molecule, the fully-interpenetrating polymer network quaternized PS4VP/PQ-10 (F-IPN QPS4VP/PQ-10) AEMs are prepared by cross-linking PS4VP and PQ-10, respectively. The as-prepared F-IPN QPS4VP/PQ-10 AEMs have obvious nanoscale microphase-separated morphologies, which ensure the membranes have good mechanical properties and dimensional stability. With optimized component ratios, F-IPN QPS4VP/PQ-10 AEM exhibits high ionic conductivity (74.29 mS/cm at 80 °C) and power density (111.83 mW/cm² at 60 °C), as well as excellent chemical stabilities (94.36% retaining of initial mass after immersion in Fenton reagent at 30 °C for 10 days, and 92.28% retaining of original ionic conductivity after immersion in 1 M NaOH solution at 60 °C for 30 days), which are greater than those of semi-interpenetrating polymer network QPS4VP/PQ-10 AEM. In summary, a combination of fully-interpenetrating polymer network and stable polymer chains and ion-conducting moieties is found to effectively overcome the trade-off between high ionic conductivity and good dimensional/chemical stabilities.     

Enhanced proton conductivity of poly (arylene ether ketone sulfone) containing uneven sulfonic acid side chains by incorporating imidazole functionalized metal-organic framework

In this study, the side-chain type hybrid proton exchange membranes which based on metal-organic frameworks (MOFs) and organic matrix of sulfonated poly (arylene ether ketone sulfone) containing both long and short sulfonic acid side chains (S-C-SPAEKS) were prepared. MOF-801 was used as a template and then imidazole was encapsulated into MOF-801 as additional proton carriers. In imidazole -MOF-801, imidazole was used as a functional group to coordinate with the zirconium metal site of the functional group. Imidazole-MOF-801 and hybrid membranes were characterized by XRD, ¹H NMR and FT-IR. These hybrid membranes exhibited excellent proton conductivities and good thermal stabilities. Compared to pure S-C-SPAEKS (0.0487 S cm^?1 at 30 °C, 0.0809 S cm^?1 at 80 °C), S-C-SPAEKS/0.5% Im-MOF-801 showed a great improvement (0.1205 S cm^?1 at 30 °C, 0.1992 S cm^?1 at 80 °C), which was about 2.5 times higher than that of pure S-C-SPAEKS and 2 times higher than that of commercial Nafion117 (0.1003 S cm^?1 at 80 °C). The results indicated that imidazole functionalized MOFs and uneven side chain structure synergistically made an important contribution to proton transport. This series of hybrid membranes have the potential to be used as alternative proton exchange membranes.     

High alkaline stability and long-term durability of imidazole functionalized poly(ether ether ketone) by incorporating graphene oxide/metal-organic framework complex

The poly(ether ether ketone) (PEEK) was prepared as organic matrix. ZIF-8 and GO/ZIF-8 were used as fillers. A series of novel new anion exchange membranes (AEMs) were fabricated with imidazole functionalized PEEK and GO/ZIF-8. The structure of ZIF-8, GO/ZIF-8 and polymers are verified by ¹H NMR, FT-IR and SEM. This series of hybrid membranes showed good thermal stability, mechanical properties and alkaline stability. The ionic conductivities of hybrid membranes are in the range of 39.38 mS cm^?1–43.64 mS cm^?1 at 30 °C, 100% RH and 59.21 mS cm^?1–86.87 mS cm^?1 at 80 °C, 100% RH, respectively. Im-PEEK/GO/ZIF-8-1% which means the mass percent of GO/ZIF-8 compound in Im-PEEK polymers is 1%, showed the higher ionic conductivity of 86.87 mS cm^?1 at 80 °C and tensile strength (38.21 MPa) than that of pure membrane (59.21 mS cm^?1 at 80 °C and 19.47 MPa). After alkaline treatment (in 2 M NaOH solution at 60 °C for 400 h), the ionic conductivity of Im-PEEK/GO/ZIF-8-1% could also maintain 92.01% of the original ionic conductivity. The results show that hybrid membranes possess the ability to coordinate trade-off effect between ionic conductivity and alkaline stability of anion exchange membranes. The excellent performances make this series of hybrid membranes become good candidate for application as AEMs in fuel cells.     

Pretreated mesocarp fibre biochars as carbon fuel for direct carbon fuel cells

This work focuses on the effect of acid and alkali pretreatment of palm mesocarp fibre (PMF) on its fuel performance in a direct carbon fuel cell (DCFC). PMF is pretreated with acid and alkali in the range of 0.1 M–4 M and followed by pyrolysis to produce biochar fuel. Performance is evaluated in the DCFC at 750 °C, 800 °C, and 850 °C. This work reveals that 2.0 M HCl treated PMF biochar gives the lowest ash value (0.1 wt%) and the highest O/C ratio among all tested biochars. The acid pretreatment contributes to enhanced electrochemical reactivity of the PMF biochar, which gives a peak power density output of 11.8 mW cm^?2 at 850 °C in the DCFC. This obtained peak power density is higher than the power density of untreated biochar, recorded at a value of 0.70 mW cm^?2. The results indicate that reduced ash, the existence of oxygen functional groups, and porous fibrous structure have increased the electro-oxidation active sites of the pretreated biochar fuel in DCFC.     

Improved proton conduction of sulfonated poly (ether ether ketone) membrane by sulfonated covalent organic framework nanosheets

A type of sulfonated covalent organic framework nanosheets (TpPa-SO₃H) was synthesized via interfacial polymerization and incorporated into sulfonated poly (ether ether ketone) (SPEEK) matrix to prepare proton exchange membranes (PEMs). The densely and orderly arranged sulfonic acid groups in the rigid skeleton of the TpPa-SO₃H nanosheets, together with their high-aspect-ratio and well-defined porous structure provide proton-conducting highways in the membrane. The doping of TpPa-SO₃H nanosheets led to an increased ion exchange capacity up to 2.34 mmol g^?1 but a 2-folds reduced swelling ratio, remarkably mitigating the trade-off between high IEC and excessive swelling ratio. Based on the high IEC and orderly arranged proton-conducting sites, the SPEEK/TpPa–SO₃H–5 membrane exhibited the maximum proton conductivity of 0.346 S cm^?1 at 80 °C, 1.91-folds higher than the pristine SPEEK membrane. The mechanical strength of the composite membrane was also improved by 2.05-folds–74.5 MPa. The single H₂/O₂ fuel cell using the SPEEK/TpPa–SO₃H–5 membrane presented favorable performance with an open voltage of 1.01 V and a power density of 86.54 mW cm^?2.     

Anion exchange membranes composed of quaternized polybenzimidazole and quaternized graphene oxide for glucose fuel cell

Glucose is one of derivative products from agriculture, possessing high theoretical energy density, non-toxicity and ease of storage, which has been of interest as a fuel in glucose fuel cell. In this work, quaternized polybenzimidazole (Q-PBI) and quaternized graphene oxide (Q-GO) were successfully functionalized by the quaternization between polybenzimidazole (PBI) and 3-bromopropyl trimethylammonium bromide (3-Br), and the reaction between graphene oxide (GO) and dimethyloctadecyl [3(Trimethoxysilyl) propyl]ammonium chloride (DMAOP), respectively. The Q-GOs with various volume fractions were embedded as the dispersed phase in the Q-PBI matrix to produce the Q-GO/Q-PBI composites as an AEM. The 0.5%v/vQ-GO/Q-PBI composite AEM showed the highest hydroxide conductivity of 1.12 ± 0.01 mS cm^?1 at 27 °C, the ion exchange capacity of 1.70 ± 0.03 mmol·g^?1, the water uptake of 66.61 ± 0.57%, and the glucose permeability of (1.79 ± 0.83) × 10^?8 cm²·s^?1. The hydroxide conductivity was higher than the commercial Fumasep® FAB-PK-130 by a factor of 23 times, whereas the glucose permeability was lower by at least an order of magnitude.     

Processing and characterization of novel Ce0.8Sm0.1Bi0.1O2-δ-BaCe0.8Sm0.1Bi0.1O3-δ (BiSDC-BCSBi) composite electrolytes for intermediate-temperature solid oxide fuel cells

Ce_0.8Sm_0.1Bi_0.1O_2-δ-BaCe_0.8Sm_0.1Bi_0.1O_3-δ (BiSDC-BCSBi) composites are fabricated as novel electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Both dramatically enhanced sinterability and electrical performance are obtained due to the Bi doping. BiSDC-BCSBi composites are densified at as low as 1200 °C, allowing a decrease of 350 °C compared with Ce_0.8Sm_0.2O_2-δ-BaCe_0.8Sm_0.2O_3-δ (SDC-BCS) composites. The optimal electrical conductivity of BiSDC-BCSBi electrolytes measured at 600 °C in humid air reaches up to 27.97 mS cm^?1, almost 6 times higher than that of SDC-BCS electrolytes (3.91 mS cm^?1 in humid air), which is mainly attributed to their lower sintering temperature, more uniform microstructure, larger tensile strains, and higher concentrations of O–H groups and oxygen vacancies. The electrolyte-supported single cell with BiSDC-BCSBi electrolyte displays a peak power density of 397 mW cm^?2 at 600 °C using humid hydrogen as fuel and ambient air as oxidant. These results imply that BiSDC-BCSBi composites have a great application prospect for IT-SOFCs.     

Poly(isatin-piperidinium-terphenyl) anion exchange membranes with improved performance for direct borohydride fuel cells

In this work, an effective design strategy for anion exchange membranes (AEMs) incorporating ether-bond free and piperidinium cationic groups promote chemical stability. A series of poly (isatin-piperidium-terphenyl) based AEMs were synthesized by superacid catalyzed polymerization reaction, followed by quaternization. The effect of functionalization on the performance of poly (isatin-N-dimethyl piperidinium triphenyl) (PIDPT-x) AEMs was investigated. Highly reactive N-propargylisatin was introduced into the backbone to achieve high molecular weight polymers (η_a = 2.06–3.02 dL g⁻¹) leading to robust mechanical properties, as well as modulating 1.78–2.00 mmol g⁻¹ of the ion exchange capacity (IEC) of the AEMs by feeding. Apart from that, the rigid non-ionized isatin-terphenyl segment provides AEMs improved dimensional stability with a swelling ratio of less than 12% at 80 °C. Among them, PIDPT-90 exhibited a higher OH⁻ conductivity of 105.6 mS cm⁻¹ at 80 °C. The alkali-stabilized PIDPT-85 AEM was presented, in which OH⁻ conductivity retention maintained 85.6% in a 2 M NaOH at 80 °C after 1632 h. Afterward, the direct borohydride fuel cells (DBFC) with PIDPT-90 membrane as a separator showed an open-circuit voltage of 1.63 V and a peak power density of 75.5 mWcm⁻² at 20 °C. This work demonstrates the potential of poly (isatin- N-dimethyl piperidinium triphenyl) as AEM for fuel cells.