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Herein, conductive and stable partially fluorinated multi-cationic alkaline membrane (AM) has been reported by macromolecular modification of poly (vinylidene fluoride) (PVDF) and chemical grafting of vinyl benzyl chloride (VBC). Quaternization was achieved using different amines, to control the concentration of quaternary ammonium (QA) groups. Different multi-cationic AMs were analysed by their structural (1H NMR and FT-IR) and morphological properties, ion-exchange capacity (IEC), water uptake (WU), alkaline conductivity (κ m ), and stabilities (mechanical, chemical, and thermal). Due to presence of multi cationic groups and thus steric hindrance, reported membranes were robust in alkaline medium. Single-cell anion exchange membrane fuel cell (AMFC) assembled with Tri-amino-VBC-g-PVDF membrane, exhibited relatively high performance (open circuit voltage (OCV): 1.03 V, peak power density: 244.0 mW cm−2 at 400.0 mA cm−2), in compare with other AMs reported in the literature. It was observed that AMFC performance was strongly depends on cationic group density, and present study explored the utilization possibility of partially fluorinated polymer matrix with multi-cationic groups for long lifetime during AMFC application. [Display omitted] • High performance partially fluorinated multi-cationic alkaline membrane. • Alkaline membrane robust for Hofmann β -elimination and SN 2 reactions. • 96.34% remained conductivity after alkali treatment at 80 °C for 768 h. • 244.0 mW cm−2 maximum power density at 400.0 mA cm−2. [ABSTRACT FROM AUTHOR]

Anion exchange membranes (AEMs) are essential in AEM water electrolysis, providing a cost-effective alternative to proton exchange membranes through the use of noble metal-free electrocatalysts. However, the "trade-off" between conductivity and dimensional stability in AEMs still hinders the development of high-performance water electrolysis. Herein, partially functionalized poly(phenylene oxide) (QPPO) is combined with poly(aryl piperidinium) (QPAP) to fabricate novel crosslinked AEMs (C-QPAP-x-QPPO), addressing the conductivity-stability issue. The crosslinked C-QPAP-x-QPPO AEMs show lower water swelling compared to their non-crosslinked QPAP membrane, mainly due to increased chain entanglements from the crosslinking process. C-QPAP-2-QPPO AEM exhibits a high conductivity of 139.4 mS cm−1 at 80 °C, attributed to the well-defined microphase separation structure. In addition, C-QPAP-2-QPPO AEM demonstrates exceptional alkaline durability, retaining over 86% conductivity and showing slight degradation after 2400 h in 1 M KOH at 60 °C. A water electrolyzer using the C-QPAP-2-QPPO achieves a maximum current density of 1440 mA cm−2 at 80 °C (2.0 V). These findings demonstrate the potential applications of crosslinked C-QPAP-x-QPPO AEMs in electrochemical devices. [Display omitted] • Functionalized poly(phenylene oxide) was used as a macromolecular crosslinker. • The crosslinked AEMs exhibited a high conductivity of 139.4 mS cm−1. • The crosslinking structure efficiently restrain the water swelling of the membrane. • The AEMs exhibited obvious microphase separation structure. • The AEMs exhibited high water electrolysis performance. [ABSTRACT FROM AUTHOR]

Hydrogen crossover that is the unwanted hydrogen permeation across the membrane driven by the difference of gas concentrations causes a critical concern of safety and efficiency for electrochemical cells, such as fuel cells and electrolyzer cells. Although the hydrogen crossover measurement in fuel cells that employ platinum based catalysts is simple and widely used in laboratory settings, it is questionable to apply existing limiting current method to water electrolyzer cells and alkaline exchange membrane (AEM) systems, which is due to the typical catalyst materials used and membrane properties, respectively. In this work, we demonstrate the operation of a compact and low-cost method of measuring hydrogen crossover that works for both AEM and proton exchange membrane (PEM) systems. The method entails a tandem configuration that utilizes an upstream crossover cell with a downstream cell in hydrogen pump configuration to measure the crossover in the cell of interest. We have successfully measured the hydrogen crossover with different membranes at various differential pressures. The developed method can be applied to catalyst-free membranes (both PEM and AEM) as well as PGM free catalyst containing cells. It will be a promising technique for measuring hydrogen crossover in-situ for a real operating membraned-based electrochemical cell or stack. [Display omitted] • A novel tandem setup is developed for measuring H 2 crossover in electrochemical cells. • The novel technique can be applied to various type of membranes. • The H 2 crossover of different membranes at various differential pressures is investigated. • The H 2 crossover of thinner membranes are more sensitive to differential pressure. [ABSTRACT FROM AUTHOR]

Alkaline membrane (AM) shows fast transport of OH− towards the anode, separates both electrodes, and prevents fuel cross-over. To achieve good membrane conductivity and performance, high concentration of positively charged groups (quaternary ammonium) is an essential requirement, which also leads excessive swelling and mechanical instability of the AMs. Further, directly grafted quaternary ammonium (QA) with main polymer chain substitution and/or elimination reactions under strong alkaline environment. To avoid above-mentioned problems, we report preparation of cross-linked chloromethylated polysulfone based AM using (4,4,-((3,3′-bis(chloromethyl)-[1.1′-biphenyl]-4,4-diyl)bis(oxy))dianiline) (BCBD), a multi-functional novel cross-linking agent. Reported strategy compensates 2 mol of chloromethyl groups consumed during cross-linking, but additional functional groups (4 mol) with cross-linking agent. These AMs are designed to avoid the nucleophilic substitution (S N 2) (grafting quaternary ammonium (QA) groups at benzylic position), and Hofmann elimination (E2) reactions (unavailability of β -H), under strong alkaline environment. Effective cross-linking has been confirmed by spectral analysis, and improves membrane stabilities and fuel cell performance. Single-cell alkaline membrane fuel cell (AEMFC) performance of most suitable (CR-QPS-03) membrane, showed comparatively high performance (open circuit voltage (OCV): 0.813 V, maximum power density: 103.6 mW/cm2 at 260.0 mA/cm2) in compare with Nafion 117 membrane (OCV: 0.682 V, maximum power density: 63.36 mW/cm2 at 220.0 mA/cm2) under similar experimental conditions. Image 1 • Multi-functional cross-linked alkaline membrane for fuel cell application. • Improved ionic nature of membrane by grafting of functional groups with cross-linker. • Alkaline stability in absence of β -hydrogen and S N 2 reaction. • CR-QPS-03 a.m. with higher fuel cell performance than Nafion 117 membrane. [ABSTRACT FROM AUTHOR]

Abstract Aliphatic alcohol mainly, ethanol, methanol and their mixture were subjected to electrooxidation study using cyclic voltammetry (CV) technique in a three electrodes half cell assembly (PGSTAT204, Autolab Netherlands). A single cell set up of direct alcohol alkaline fuel cell (DAAFC) was fabricated using laboratory synthesized alkaline membrane to validate the CV results. The DAAFC conditions were kept similar as that of CV experiments. The anode and cathode electrocatalysts were Pt-Ru (30%:15% by wt.)/Carbon black (C) (Alfa Aesar, USA) and Pt (40% by wt.)/High Surface Area Carbon (C HSA) (Alfa Aesar, USA) respectively. The CV and single cell experiments were performed at a temperature of 30 °C. The anode electrocatalyst was in the range of 0.5 mg/cm2 to 1.5 mg/cm2 for half cell CV analysis. The cell voltage and current density data were recorded for different concentrations of fuel (ethanol or methanol) and their mixture mixed with different concentration of KOH as electrolyte. The optimum electrocatalyst loading in half cell study was found to be 1 mg/cm2 of Pt-Ru/C irrespective of fuel used. The single cell was tested using optimum anode loading of 1 mg/cm2 of Pt-Ru/C which was found in CV experiment. Cathode loading was kept similar, in the order of 1 mg/cm2 Pt/C HSA. In single cell experiment, the maximum open circuit voltage (OCV) of 0.75 V and power density of 3.57 mW/cm2 at a current density of 17.76 mA/cm2 were obtained for the fuel of 2 M ethanol mixed with 1 M KOH. Whereas, maximum OCV of 0.62 V and power density of 7.10 mW/cm2 at a current density of 23.53 mA/cm2 were obtained for the fuel of 3 M methanol mixed with 6 M KOH. The mixture of methanol and ethanol (1:3) mixed with 0.5 M KOH produced the maximum OCV of 0.66 V and power density of 1.98 mW/cm2 at a current density of 11.54 mA/cm2. Highlights • Ethanol shows promising result in a mixture of methanol and ethanol. • Low cost PVA based alkaline membrane was successfully synthesized in laboratory. • The ionic conductivity of the PVA based alkaline membrane was excellent. • PVA based alkaline membrane is suitable for low temperature application. [ABSTRACT FROM AUTHOR]

Abstract: A polyvinyl alcohol (PVA) based alkaline membrane was developed in the laboratory for use in direct methanol fuel cell (DMFC). This study investigates the performance of the alkaline PVA membrane, crosslinked by a physical crosslinking method. The membrane was characterized using water uptake, KOH uptake, ion exchange capacity, and ionic conductivity methods. The anode and cathode electrocatalysts were Pt‐Ru (30:15 % by wt)/carbon black (C) and Pt (40 % by wt)/high surface area carbon (CHSA), respectively. A similar electrocatalyst loading in the order of 1 mg/cm2 was used at the anode and cathode. The cell voltage and current density data were recorded for different concentrations of fuel (methanol) and electrolyte (KOH). The optimum conditions for the fuel cell were 2 M methanol mixed in 3 M KOH solution at a flow rate of 2 mL/min with a cathode feed of humidified oxygen at a flow rate of 100 mL/min. The DMFC was operated at 30 °C, irrespective of other operating conditions. The maximum open circuit voltage of 0.6 V, current density of 7.71 mA/cm2 at a cell voltage of 0.23 V, and maximum power density of 1.79 mW/cm2 were obtained at the optimum cell condition. The KOH‐doped PVA solid electrolyte was successfully tested in a direct methanol fuel cell, which results in excellent power density. Single cell test results prove that the physically crosslinked KOH‐doped PVA electrolyte could be used as a suitable solid electrolyte in a fuel cell. [ABSTRACT FROM AUTHOR]

This article describes the development of a high power density Direct Formate Fuel Cell (DFFC) fed with potassium formate (KCOOH). The membrane electrode assembly (MEA) contains no platinum metal. The cathode catalyst is FeCo/C combined with a commercial anion exchange membrane (AEM). To enhance the power output and energy efficiency we have employed a nanostructured Pd/C-CeO2 anode catalyst. The activity for the formate oxidation reaction (FOR) is enhanced when compared to a Pd/C catalyst with the same Pd loading. Fuel cell tests at 60 °C show a peak power density of almost 250 mW cm-2. The discharge energy (14 kJ), faradic efficiency (89%) and energy efficiency (46%) were determined for a single fuel charge (30 mL of 4 M KCOOH and 4 M KOH). Energy analysis demonstrates that removal of the expensive KOH electrolyte is essential for the future development of these devices. To compensate we apply for the first time a polymeric ionomer in the catalyst layer of the anode electrode. A homopolymer is synthesized by the radical polymerization of vinyl benzene chloride followed by amination with 1,4-diazabicyclo[2.2.2]octane (DABCO). The energy delivered, energy efficiency and fuel consumption efficiency of DFFCs fed with 4 M KCOOH are doubled with the use of the ionomer. [ABSTRACT FROM AUTHOR]

The effects of different temperatures (55, 65, 75 and 85 °C) and cathode gas compositions (O2, synthetic air, air and 90% synthetic air+10% CO2) on alkaline anion exchange membrane fuel cell (AAEMFC) were evaluated. Membrane electrode assemblies (MEA) were fabricated using commercial anion exchange membrane (AEM) in OH- form and Pt catalyst. Polarization curves and voltage responses during constant current were performed in order to describe the influences of temperature and gas composition on the AAEMFC performance. The experimental results showed that the fuel cell performance increases with elevating temperatures for all applied gas compositions. Highest power density of 34.7 mW cm-2 was achieved for pure O2 as cathode feed. A decrease to 20.3 mW cm-2 was observed when cathode gas composition was changed to synthetic air due to reduction of the O2 partial pressure. The presence of CO2 in atmospheric air applied to the cathode stream caused a further drop of the maximum power density to 15.2 mW cm-2 driven by neutralization of OH- ions with CO2.

This study focused on the design and fabricating of a new type of hydroxyl anion conducting membranes employing the interpenetrating polymer network (IPN) comprising poly (vinyl alcohol) (PVA) and linear structured poly bis(2-chloroethyl) ether-1,3-bis [3-(dimethylamino)propyl] urea copolymer (PUB). The membranes are synthesized through blending assisted by a simple chemical cross-linking process. Various characterizations are conducted including Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), gravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS) and AC impedance. Results revealed that by simply tuning the mass fraction of PUB (the content of PUB changed from 20%–50%) in the membrane, the OH – conductivity (10 − 2 S cm − 1 at 80 °C, fully hydrated membranes) with high extensibility (at break in the range of 200–400%) and tensile stress (at break around 15–30 MPa, ∼ 50% relative humidity) are achieved. XPS analysis reveals that a slight degradation occurs when the membrane is exposed to exceedingly tough conditions such as 8 M KOH at 80 °C for 240 h, but the OH – conductivity is changed insignificantly. When assembled in a real H 2 /O 2 alkaline fuel cell, the initial peak power densities in the range of 5.7–28.6 mW cm − 2 and an open circuit potential reaching to 1.0 V are obtained for MEAs fabricated with these membranes at 25 °C. [ABSTRACT FROM AUTHOR]

A series of anion exchange membranes of poly (fluorenylene ether sulfone) containing tertiary sulfonium hydroxide-functionalized fluorenyl groups were synthesized by sequential polycondensation, chloromethylation, substitution with dimethyl sulfide and ion exchange. They showed excellent solubility in polar aprotic solvents. Consequently, flexible and tough alkaline membranes with varying ionic contents were obtained by an anion exchange of tertiary sulfonium chloride polymers with 1.0 M KOH at room temperature. Different levels of substitution were performed to achieve high ionic conductivity as well as upholding the membranes’ mechanical stability. The tertiary sulfonium membranes demonstrated lower water uptake compared to quaternary ammonium membrane. High hydroxide ion conductivity was achieved up to 18.3 mS cm −1 at 80 °C with the membrane of the highest ion exchange capacity (IEC, 1.51 mmol g −1 ). The resulting alkaline polymers were characterized by 1 H NMR, FT-IR, thermogravimetric analysis (TGA), water uptake, IEC, atomic force microscopic (AFM) images. [ABSTRACT FROM AUTHOR]

This article describes the development of a high power density Direct Formate Fuel Cell (DFFC) fed with potassium formate (KCOOH). The membrane electrode assembly (MEA) contains no platinum metal. The cathode catalyst is FeCo/C combined with a commercial anion exchange membrane (AEM). To enhance the power output and energy efficiency we have employed a nanostructured Pd/C-CeO2 anode catalyst. The activity for the formate oxidation reaction (FOR) is enhanced when compared to a Pd/C catalyst with the same Pd loading. Fuel cell tests at 60 °C show a peak power density of almost 250 mW cm−2. The discharge energy (14 kJ), faradic efficiency (89%) and energy efficiency (46%) were determined for a single fuel charge (30 mL of 4 M KCOOH and 4 M KOH). Energy analysis demonstrates that removal of the expensive KOH electrolyte is essential for the future development of these devices. To compensate we apply for the first time a polymeric ionomer in the catalyst layer of the anode electrode. A homopolymer is synthesized by the radical polymerization of vinyl benzene chloride followed by amination with 1,4-diazabicyclo[2.2.2]octane (DABCO). The energy delivered, energy efficiency and fuel consumption efficiency of DFFCs fed with 4 M KCOOH are doubled with the use of the ionomer.

In this work, OH– conducting membrane based on bacterial cellulose (BC) had been synthesized via modification with Poly(diallyldimethyl-ammonium chloride) (PDDA) and Poly(vinyl alcohol) (PVA) of different molecular weights using layer by layer method assisted by double cross-linking process. OH– conductivity and water uptake were intensively investigated by changing crosslinking conditions, KOH concentrations and different PVA molecular weights. Containing the maximum σ OH − reached up to 72.95 mS cm−1 at room temperature with water uptake being 877%, the LPVA-PDDA-BC-OH– membrane showed the lowest calculated activation energy value of 10.211 KJ mol−1 indicating that both Grotthus and vehicle mechanisms played an important role on ionic transportation. During the application of CO 2 electrochemical reduction (CO 2 ER) in 0.5 M KHCO 3 , the current density could reach up to 47.44 mA cm−2 at −1.06 V RHE while FE HCOO − achieved the maximum value of 67.89% which dampened only 7.09% after 20 h electrolysis. Furthermore, being assembled into the flexible zinc-air batteries (F-ZAB), the LPVA-PDDA-BC-OH– membrane exhibited excellent power density of 130.3 mW cm−2 at room temperature. [Display omitted] • Bacterial cellulose-based AEMs prepared by layer-by-layer/double-crosslinking method. • OH– conductivity achieves 72.95 mS/cm at room temperature and 133.53 mS/cm at 80 °C. • The current density of 51.34 mA/cm2 at potential −1.36 V RHE can be achieved. • The Faradaic efficiency of format reaches up to 67.89% at −1.06 V RHE. • OCV (1.42 V) and peak zinc-air battery power density (130.3 mW/cm2) can be achieved. Through the combinations of layer-by-layer method and double cross-linking process, OH– conducting membrane based on bacterial cellulose (BC) had been synthesized with the modification by Poly (diallyldimethyl-ammonium chloride) (PDDA) and Poly (vinyl alcohol) (PVA) of different molecular weights. Under the help of PVA, an enhanced internal three-dimensional network could be easily constructed to overcome the disadvantage of excessively loosely binding in the BC membrane. Charge carrier PDDA were confirmed by FTIR and SEM to be firmly embedded into the network while studies on XRD and DSC indicated that amorphous content which was beneficial to ionic transfer and ions hopping held the large proportion in the membrane. Stability measurements such as thermogravimetric analysis, mechanical properties, alkaline and oxygen resistance were carried out, showing that the prepared membranes possessed excellent durable performance under various extreme conditions. Moreover, OH– conductivity and water uptake were intensively investigated by changing crosslinking conditions, KOH concentrations and PVA molecular weights. Achieving the maximum σ OH − of 72.95 mS cm−1 at room temperature, the LPVA-PDDA-BC-OH– membrane showed the lowest calculated activation energy value of 10.211 KJ mol−1, indicating that both Grotthus and vehicle mechanisms played an important role on ionic transportation. When as-prepared LPVA-PDDA-BC-OH– membrane was applied for CO 2 electrochemical reduction (CO 2 ER) in 0.5 M KHCO 3 , current density could reach up to 47.44 mA cm−2 at −1.06 V RHE. Meanwhile, Faradaic efficiency for formate (FE HCOO −) could achieve the maximum value of 67.89 % that dampened only 7.09 % after 20 h electrolysis. Furthermore, when as-prepared LPVA-PDDA-BC-OH– membrane was assembled into the flexible zinc-air batteries (F-ZAB), excellent power density of 130.3 mW cm−2 could be obtained at room temperature. [ABSTRACT FROM AUTHOR]

One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm−2. [ABSTRACT FROM AUTHOR]

This study addresses the physico-chemical characterization of KOH-doped polybenzimidazole (PBI, poly[2,2-(m-phenylene)-5,5-bibenzimidazole]) membranes for application in alkaline direct glycerol fuel cells. The KOH-doped membranes present a large affinity for water and gradually replace the acid hydrogens in the imidazole rings with K. Only at KOH concentrations above 4 mol L −1 are “free” KOH molecules present in the membrane structure, along with a small fraction of glycerol molecules. These behaviours impact on the membrane dimensions. At KOH concentrations below 4 mol L −1 , the membrane dimensions become enlarged. However, at higher concentrations, the cross-sectional area shrinks, whereas the thickness expands significantly. This result is confirmed by x-ray diffraction, where an enlargement in the inter-chain distances is evidenced. The infrared spectra support the interaction of KOH and PBI at alkali concentrations of 4 mol L −1 or higher, though reveal some membrane degradation processes. The KOH-doped PBI membranes present thermal stabilities up to 573 K, a coefficient of permeability to glycerol of around 10 −7 cm 2 s −1 , and OH − conductivities above 0.01 S cm −1 at temperatures between 303 and 348 K. The combination of these parameters configures a suitable alkaline membrane capable of producing a maximum power density of 34.2 mW cm −2 for 1 mol L −1 glycerol and 4 mol L −1 KOH at 348 K. [ABSTRACT FROM AUTHOR]

Herein, we are disclosing simple route for the preparation of alkaline membranes (AMs) based on aminated multiblock poly(arylene ether)s (AMPEs) synthesized by nucleophilic substitution-poly condensation followed by quaternization and alkalization reactions. In this procedure, four quaternary ammonium groups are successfully introduced without use of carcinogenic reagents such as chloromethylmethyl ether (CMME). Hydrophilic/hydrophobic phase separation is responsible for their high hydroxide conductivity (∼150 mS cm −1 at 80 °C) due to development of interconnected ion transport pathway. AMs are exhibiting good alkaline stability due to the presence of two vicinal quaternary ammonium groups and avoid degradation such as Sommelet–Hauser rearrangement and Hofmann elimination. Vicinal quaternary ammonium groups also resist nucleophilic (OH − ) attack and suppress the Stevens rearrangement as well as S N 2 substitution reaction due to stearic hindrance. Optimized AM (AMPE-M20N15 (55% DCM)) exhibits about 0.95 V open circuit voltage (OCV) and 48.8 mW cm −2 power density at 65 °C in alkaline direct methanol fuel cell (ADMFC) operation. These results suggest promising begin for the preparation of stable and conductive AMs for ADMFC applications and useful for developing hydroxide conductive materials. [ABSTRACT FROM AUTHOR]

An OH− conductive anion exchange membrane was prepared by a pore-filling method with porous polytetrafluoroethylene and a quaternary ammonium polymethacrylate ionomer. The composite membrane exhibited less swelling ratios of thickness and area variation and stronger tensile strength than the pristine polymethacrylate membrane. The ionic conductivity of the composite membrane was not as good as the pristine polymethacrylate ionomer membrane. However, the composite membrane was ultra-thin therefore it leaded to a smaller ionic resistance of the MEA and improved current densities. In fuel cell mode, the peak power densities were respectively 0.114 and 0.163 W cm−2 at 20 and 45 °C. In water electrolyser mode, at a current density of 100 mA cm−2 the cell voltages were about 1.61 V and 1.52 V respectively at 22 °C and 50 °C. In the water electrolyser mode, the degradation rate was only 0.0379 mV h−1 after 120 h at a current density of 100 mA cm−2 at 22 °C. [ABSTRACT FROM AUTHOR]

Abstract: The performance of an alkaline Direct Formate Fuel Cell (DFFC) employing a polymer anion exchange membrane has been greatly improved by optimization of the method and amount of catalyst loading at the anode. An optimum anode for this DFFC was obtained by a combination of direct-membrane spray painting and gas diffusion layer brush painting. When this fuel cell was operated at 60 °C with 1 M HCOOK, 2 M KOH, and oxygen, its current density at 0.6 V was 408 mA cm−2, and its maximum power density was 267 mW cm−2. When KOH was removed from the fuel stream, a power density of 157 mW cm−2 was achieved. Both of these power densities are very competitive with recent reports of alkaline direct liquid fuel cells (DLFC). We also demonstrate the DFFC when air was used at the cathode and no KOH was added to the fuel; the maximum power density was 105 mW cm−2 in this case. [Copyright &y& Elsevier]

Abstract: The basic concept of methanol–water solution electrolysis with an alkaline membrane and the experimental studies are presented. The measurements were performed with a membrane electrode assembly consisting of an anion exchange membrane, Pt/C cathode and either PtRu/C or Pt/C anode. Hydrogen production efficiency was measured and the effects of temperature and methanol concentration on the electrolysis performance were investigated. PtRu was found to be a better catalyst at low potentials and the hydrogen was produced with a high efficiency. The results indicate that the favored kinetics and mass transport at high temperatures result in increased hydrogen production. Additionally, it was found that, increasing methanol concentration decreased the performance of the electrolysis as the membrane morphology changes as a function of the concentration. [Copyright &y& Elsevier]

Abstract: Using computational approaches we predict the microstructure of high-performance alkaline polymer, quaternary ammonium polysulfone hydroxide (QAPS-OH) membranes, dry and with ∼14wt% water uptake. The microstructure can be described as a hydrophobic polymer backbone penetrated by a network of three-dimensional interlinked hydrophilic channels of different diameters. Mobile OH-anions are distributed inside the channels. OH diffusion coefficients and corresponding activation energy were calculated from our molecular dynamics simulations of the QAPS-OH membrane at different temperatures. The predicted values are consistent with available experimental data. Possible mechanisms of the OH-anion diffusion have been discussed. [Copyright &y& Elsevier]

Abstract: Poly(ether ether ketone) (PEEK) was dissolved in conc. H2SO4 and its chloromethylation was achieved in presence of paraformaldehyde, trimethylchlorosilane and Lewis acid catalyst, obtained about 35–75% degree of chloromethylation (DCM). This idea is based on partial sulfonation of PEEK to make it soluble and further complete replacement of –SO3H with –CH2Cl groups. Alkaline membranes (AMs) were prepared by quaternization of chloromethylated PEEK (CMPEEK). The reported method is a “green” alternative for the production of AEM without the use of hazardous chemicals (such as chloromethyl methyl ether, chloromethyloctylether, bis(chloromethyl) ether etc.). Chronopotentiometry study of prepared membranes confirmed their homogeneous and alkaline nature suitable for methanol fuel cells. The AMs exhibit a splendid chemical stability at 10M KOH. Alkaline conductivity of quaternized poly(ether ether ketone) membrane with 75% DCM (QPEEK-75) (14.63mScm−1) in equilibration with deionized water was relatively high in compare with other AMs reported in the literature. For the H2/air single fuel cell at 50°C with QPEEK-75 membrane, about 1.02V OCV and 48.09mWcm−2 power density at 109.3mAcm−2 current density were obtained. [Copyright &y& Elsevier]

Abstract: A series of poly(arylene ether sulfone)s containing tetra-quaternary ammonium hydroxide on fluorenyl group (QAPAES-OH) were synthesized via polycondensation, chloromethylation, quaternization, and the subsequent ion exchange reactions. The tetra-quaternary ammonium hydroxide polymers rendered an elevated molecular weight and exhibited an outstanding solubility in aprotic polar solvents. Consequently, flexible and tough alkaline membranes with varying ionic contents were obtained by an anion exchange of tetra-quaternary ammonium chloride polymers with 1.0M KOH at room temperature. Quaternization and the following ion exchange reactions were quantitative so that the obtained ionomer membranes could have high ion exchange capacity (IEC) upto 1.73mmolg−1. High hydroxide ion conductivity was achieved up to 30.7mScm−1 at 80°C with the membrane of the highest IEC. The resulting polymers were characterized by 1H NMR, FT-IR, and TGA. [Copyright &y& Elsevier]

Abstract: We demonstrate for the first time an operating Direct Formate Fuel Cell employing formate salts as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, and metal catalysts at the anode and cathode. Operation of the DFFC at 60 °C using 1 M KOOCH and 2 M KOH as the anode fuel and electrolyte and oxygen gas at the cathode produces 144 mW cm−2 of peak power density, 181 mA cm−2 current density at 0.6 V, and an open circuit voltage of 0.931 V. This performance is competitive with alkaline Direct Liquid Fuel Cells (DLFCs) previously reported in the literature and demonstrates that formate fuel is a legitimate contender with alcohol fuels for alkaline DLFCs. A survey of the literature shows that a formate–oxygen fuel cell has a high theoretical potential, and the safe, renewable formate fuel does not poison the anode catalyst. [Copyright &y& Elsevier]

An investigation of the carbon-supported iron phthalocyanine (Fe-Pc) catalyst for oxygen reduction reaction (ORR) in alkaline media and in hydrogen fuel cells is described. The non-noble metal Fe-Pc catalyst is shown to be a promising alternative to platinum for ORR in alkaline media, with onset potentials of ca. 15 mV higher and double the mass activity than that of Pt. The catalyst also showed lower peroxide generation at lower voltages than Pt when tested at a rotating ring disc electrode. The effect of various parameters such as catalyst loading, catalyst layer thickness, fabrication technique, and ionomer on a hydrogen fuel cell performance using an alkaline electrolyte membrane made by radiation grafting is described. Peak power densities of the fuel cell with Pt/C oxygen reduction catalysts were greater than 100 mW/cm at 60 °C using air. The performance of the fuel cell with the Fe-Pc catalyst was inferior to that with the Pt catalyst giving approximately half the peak power density initially due to the thicker catalyst layer and instability in the quaternary ammonium environment. However, the performance of the Fe-Pc catalyst under fuel cell conditions was found to fall with time due to an interaction of the catalyst with the ion-exchange group of the membrane and the ionomer used in the catalyst layer. [ABSTRACT FROM AUTHOR]

Abstract: We synthesized a new type of alkaline electrolyte membrane by use of aminoethylaminopropylmethyldimethoxysilane via sol–gel technique. The ionic conductivity of the membrane was estimated to be 1.0×10−4 S/cm at 80°C from AC impedance method. The power density of the fuel cell was 7.6×10−4 W/cm2 while the current density was 2.2mA/cm2 at 0.35V of potential when the cell was kept at 40°C. [Copyright &y& Elsevier]

The mechanism of the thermal decomposition of [NMe4][OH]·5H2O, tetramethyl ammonium hydroxide pentahydrate, was studied using DSC, TG and evolved gas analysis because of the importance of related ions in anion exchange membranes. The products of the reaction are trimethyl amine, methanol and dimethyl ether. The relative ratio of the products is determined by how much water remains in the sample as it is decomposing. Isotopic labeling experiments with D2O show that deprotonation of the tetramethyl ammonium ion by hydroxide establishes a rapid equilibrium between tetramethyl ammonium ion and the nitrogen ylide species and water that scrambles the deuterium with the proton in the methyl groups. The results of this work also suggest that tetraalkyl ammonium cations may be more stable in hydroxide conducting membranes than previously believed. [ABSTRACT FROM AUTHOR]

Abstract: A solid-state cell is used to study the electrocatalysis of oxygen reduction at the silver/hydroxide-exchange membrane interface. The catalyst/membrane interface exhibits improved performance in comparison to a catalyst/aqueous sodium hydroxide interface. Surprisingly, the half-wave potential for oxygen reduction is shown to shift 185mV higher at the silver/hydroxide-exchange membrane interface than for the silver/aqueous hydroxide solution interface, and the exchange current density is significantly higher at 1.02×10−6 Am−2. On a cost per performance basis, silver electrocatalysts in a hydroxide-exchange membrane fuel cell may provide better performance than platinum in a proton-exchange membrane fuel cell. [Copyright &y& Elsevier]

Abstract: A series of radiation-grafted alkaline anion-exchange membranes (AAEMs) with degrees of grafting (by mass) in the range 20–26% were produced and characterised. Conductivities (from impedance spectroscopy) up to 0.023±0.001 S cm−1 at 50±1 °C were demonstrated, which are between 20–50% of values for the commercial acid-form membrane Nafion®-115 [N115; σ=0.045±0.004 (65 °C)–0.104±0.008 (50±1 °C) S cm−1, depending on the level of hydration (10 and 23 water molecules per sulfonate group, respectively)]. This significant result clearly indicates the suitability of these AAEMs for application in fuel cells at temperatures below the widely accepted alkaline membrane thermal stability limit of 60 °C. Statistical analysis of the results of ion-exchange capacity and conductivity studies on the AAEMs indicates the presence of heterogeneity in the grafting levels within the AAEMs and suggests that more synthetic optimization work is required. The empirical activation energies (Arrehnius behaviour assumed) for the hydroxide ion migration in the AAEMs (12.6±0.6 kJ mol−1 at the 95% confidence level) are twice the value for proton migration found for fully hydrated Nafion®-115 (6.0±0.8 kJ mol−1) and show that hydroxide ion mobility is more strongly temperature-dependent. [Copyright &y& Elsevier]

As the proton exchange membrane direct methanol fuel cell (PEMDMFC) faces sustaining obstacles, alkaline membrane direct methanol fuel cell (AMDMFC) is attracting increasing attention. Although some advantages may be expected, the feasibility of AMDMFC does not seem well verified. In this paper, thermodynamic disadvantages and kinetic advantages of AMDMFC are elucidated. In thermodynamic aspect, a large voltage loss due to the pH difference across the membrane is predicted by theoretical calculation; in kinetic aspect, besides the well-known superiority of alkaline media for oxygen reduction, experimental data show much higher anodic performance in carbonate/bicarbonate than in acid. In-situ FTIR measurements indicate that methanol can be fully oxidized to carbon dioxide in carbonate/bicarbonate as in sulfuric acid. Taking into account all the foreseeable advantageous and disadvantageous factors, AMDMFC is worth study, and an alkaline membrane stable at elevated temperatures is the prerequisite for a successful AMDMFC. [Copyright &y& Elsevier]

Development of thin, dense and robust alkaline polymer membranes with high hydroxide ion conductivity is key to advanced alkaline electrolysis as it can enable operation at higher current density and/or efficiency, while improving the dynamic response of the electrolyzer. In this work, a homogeneous blend membrane system based on poly(arylene ether sulfone) (PSU) and poly(vinylpyrrolidone) (PVP) is explored as an alkaline ion-solvating polymer matrix. Increasing PVP content in the blend drastically increases electrolyte uptake, and at PVP contents higher than 45 wt%, the membrane can support ion conductivity in a technologically relevant range of 10–100 mS cm-1 or even higher when equilibrated in 20 wt% aqueous KOH. The membrane system is extensively characterized throughout the full composition range and the down-selected composition composed of 25% PSU and 75% PVP is employed in a single cell lab-scale water electrolyzer, showing excellent performance and stability during the course of one week at 500 mA cm-2 at 60 °C in 20 wt% KOH. Good performance stability was demonstrated for more than 700 h at 80 °C, but the gradually increasing KOH concentration due to evaporative loss of water resulted in membrane degradation. Image 1 • Polysulfone and poly(vinylpyrrolidone) blends prepared in full composition range. • Water and electrolyte uptake increase with increasing poly(vinylpyrrolidone) content. • Conductivity exceeding 100 mS cm-1 in aqueous KOH. • Stable alkaline electrolysis performance over 1 week demonstrated. [ABSTRACT FROM AUTHOR]