Development Of New Membranes Research Articles

Development of Pentablock Copolymer Membranes for a Sodium Polysulfide Hybrid Redox Flow Battery

Long duration energy storage devices, such as redox flow batteries (RFBs), are critical for enabling the widespread adoption of renewable energy sources such as wind and solar on the electric grid. Non-aqueous RFBs (NARFBs) have emerged as a possible alternative to aqueous RFBs (e.g., all-vanadium and Zn/Br systems), as they have the potential to use supporting electrolytes with wide operating voltage windows (>3 V) and a variety of redox couples. One NARFB of interest is a hybrid RFB that utilizes an alkali metal anode, such as sodium, and a polysulfide catholyte. However, the realization of a hybrid NARFB for long duration energy storage requires the development of new membranes with robust mechanical properties, good (electro)chemical stability, high ionic conductivity, and low polysulfide permeability. In this work, we have utilized a cation exchange pentablock copolymer membrane with sodium sulfonate and sodium trifluoromethanesulfonimide (TFSI) functionalities. We studied various crosslinking methods with the goal of reducing electrolyte uptake and polysulfide crossover of the membrane, while maintaining high ion transport. One lightly crosslinked membrane exhibits a 40% reduction in electrolyte uptake compared to the uncrosslinked membrane, but at the expense of a reduction in ionic conductivity from 2.5 x 10-4 S/cm to 4.2 x 10-5 S/cm at 20 °C. Our continued efforts in developing techniques to improve membrane properties will also be discussed.

Metal Recovery from Wastewater Using Electrodialysis Separation

Electrodialysis is classified as a membrane separation process in which ions are transferred through selective ion-exchange membranes from one solution to another using an electric field as the driving force. Electrodialysis is a mature technology in the field of brackish water desalination, but in recent decades the development of new membranes has made it possible to extend their application in the food, drug, and chemical process industries, including wastewater treatment. This work describes the state of the art in the use of electrodialysis (ED) for metal removal from water and wastewater. The fundamentals of the technique are introduced based on the working principle, operational features, and transport mechanisms of the membranes. An overview of the key factors (i.e., the membrane properties, the cell configuration, and the operational conditions) in the ED performance is presented. This review highlights the importance of studying the inter-relation of parameters affecting the transport mechanism to design and optimize metal recovery through ED. The conventional applications of ED for the desalination of brackish water and demineralization of industrial process water and wastewater are discussed to better understand the key role of this technology in the separation, concentration, and purification of aqueous effluents. The recovery and concentration of metals from industrial effluents are evaluated based on a review of the literature dealing with effluents from different sources. The most relevant results of these experimental studies highlight the key role of ED in the challenge of selective recovery of metals from aqueous effluents. This review addresses the potential application of ED not only for polluted water treatment but also as a promising tool for the recovery of critical metals to avoid natural resource depletion, promoting a circular economy.

Bioinspired humic acid-based membranes for water desalination: Mechanistic insights from molecular simulations

Bioinspired membranes have received considerable interest for separation, but their design is challenging because of lack in fundamental understanding of separation mechanism involved. Herein, we explore renewable humic acid (HA)-based bioinspired membranes for water desalination via molecular simulations. Different HA membranes (monomeric, Y- and star-crosslinked) with microscopic “ridge-and-valley” patterned pore structures are constructed. With the existence of intermolecular hydrogen bonds, the HA membranes possess good mechanical strength with Young's moduli ranging from 0.44 to 1.64 GPa. Water desalination performance of the HA membranes is comprehensively examined in 12 salt solutions with different cations (Mg2+, Ca2+, Li+, Na+, K+ and NH4+) and anions (CO32−, SO42−, F−, OH−, Cl− and NO3−), respectively. Water and ion in the HA membranes are revealed to follow a dynamical “hopping-transport” mechanism. The HA membranes exhibit superior desalination performance, comparable to commercial reverse osmosis membranes and graphene oxide membranes. Interestingly, water flux in the monomeric HA membrane is enhanced by tailoring the membrane structure from monomeric to crosslinked architecture. Upon varying cation or anion in a salt solution, salt rejection drops when ion hydration level decreases. From bottom-up, the simulations provide mechanistic insights into water desalination and would facilitate the development of new membranes for high-performance water desalination.

A benzimidazole-linked polymer membrane in alkaline water electrolysis

Advanced alkaline water electrolysis for hydrogen production necessitates the development of new membranes with high ionic conductivity, gas-tightness, and structural robustness in the alkaline environment. To this end, a benzimidazole-linked polymer (BILP) based composite membrane is prepared by forming a BILP-101 dense layer via interfacial polymerization (IP) on top of a commercial porous polyethylene (PE) substrate membrane. The density and thickness of the dense layer are easily adjustable by changing the acid content in the aqueous phase and the IP time, respectively. The BILP-PE composite membranes exhibit an area resistance of only ∼75 mΩ cm2 at 30 °C and <30 mΩ cm2 at 80 °C in 1 M KOH. While their H2 gas crossover rate is ∼4 × 10−14 mol cm s−1 cm−2 kPa−1, nearly two orders of magnitude lower than that of commercial Zirfon UTP-500 diaphragm. The BILP-PE membranes also show a very low swelling ratio of ∼4% and high tensile strength of >100 MPa. Soaking in 30 wt% KOH solution at 60 °C, the BILP dense layers would lose their weight at an ever-decreased speed and come to a halt after ∼24 d of soak, with a total loss of <10% of their original weight. The BILP-PE composite membrane looks very promising in advanced alkaline water electrolysis.

Synergizing machine learning, molecular simulation and experiment to develop polymer membranes for solvent recovery

Organic solvent nanofiltration (OSN) is a robust membrane technology for solvent recovery and molecular separation in harsh conditions. However, the current OSN membranes are largely produced through trial-and-error methods. In this study, machine learning (ML), molecular simulation (MS) and experiment are synergized for the development of OSN membranes. Using three different learning strategies, ML models are first constructed to identify critical gross properties (i.e., solvent viscosity, membrane thickness and water contact angle) and establish a phenomenological relationship for permeability prediction. Subsequently, ML models based on molecular representation via concatenated fragments are developed to predict methanol permeabilities in three polymer of intrinsic microporosity (PIM) membranes (PIM-A1, CX-PIM-A1 and PIM-8). The methanol permeability predicted in PIM-A1 is the highest among the three and also higher than that in archetypal PIM-1. Next, MS is conducted to provide microscopic insights into swelling behavior and methanol permeation in the three PIM membranes. Finally, the PIM-A1 membrane is experimentally fabricated and found to exhibit nearly complete solute rejection and methanol permeability of 2.33 × 10−6 L·m/m2·h·bar, which validates the ML prediction. This study demonstrates that the synergy of ML, MS and experiment can fundamentally elucidate and quantitatively predict solvent permeation in polymer membranes, and the holistic approach may advance the development of new membranes for solvent recovery and other important separation processes.

Wetting of photoplasmonic PVDF/silver membranes in photothermal membrane distillation: Identification of wetting mechanisms and comparison of wetting dynamics

Photothermal membrane distillation (PMD) is a promising configuration of membrane distillation (MD), which can overcome the temperature polarization problem and allows using solar thermal energy. However, the effect on wetting of the incorporation of plasmonic nanoparticles (NPs) into a membrane is still unknown. This paper aims supporting the development of photoplasmonic membranes for PMD, by studying their wetting in vacuum MD operation, thanks to two methods recently developed in our group: the ex-situ detection of dissolved tracer intrusion (DDTI) and an in-operando optical method. Different composite membranes with Ag-NPs included in PVDF were elaborated by phase-inversion for checking if the proportion of NPs influences membrane wetting. This study demonstrates the importance of considering wetting in the earlier stages of the development of new membranes. Indeed, whatever the NP load, at global scale partial wetting was detected and the pore wetting ratio increased with the NP load, whereas the PVDF membrane remained un-wetted. Wetting dynamics was highly impacted by the presence of NPs and wetting occurred faster with increasing NP load, thus reducing the duration of the MD operation for the highest load. For limiting short-term wetting, a limited proportion of Ag-NPs (≤25 %) is recommended to membrane manufacturers or developers.

Partially oxidised boron nitride as a 2D nanomaterial for nanofiltration applications.

Boron nitride (BN) based 2D nanomaterials are an emerging class of materials for the development of new membranes for nanofiltration applications. Here, we report the preparation, characterisation and testing of highly promising nanofiltration membranes produced from partially oxidised BN (BNOx) 2D nanosheets. In our work, the partial oxidation of BN was successfully achieved by heating the bulk h-BN powder in air at 1000 °C, resulting in BNOx product. The characterisation of the sample showed the presence of B-OH groups corresponding to the partial oxidisation of the BN. The BNOx material was then exfoliated in water and used to produce membranes, using vacuum filtration. These membranes were characterised using electron microscopy, BET and mercury porosimetry techniques. The membranes have also been tested in water purification and removal of several typical water-soluble dyes, demonstrating outstanding retention values close to 100%. We believe that this research opens up new opportunities for further production, as well as chemical functionalisation and modification of membranes for nanofiltration and separation technologies.

(Invited) High-Throughput, In-line Quality Control of Fuel Cell Materials

Electrochemical energy conversion technologies are actively being commercialized for large-scale applications, such as zero-pollution automotive systems. There has been significant progress in pioneering research, such as the discovery and development of new membranes, catalysts, gas diffusion layers, membrane electrode assemblies, and operating conditions. These technologies need to make the jump from laboratory research-scale to robust production-scale. In many cases, scale up requires compromises on materials, methodology, and quality control of each component. Current manufacturing practices generally rely heavily on manual, visual inspection of individual components followed by cell testing to indicate material issues, which leads to delayed correction of production issues and added cost in the form of additional labor and expensive material loss. Reducing the extent of the manual labor and compromises during scale up requires addition and integration of in-line, real-time, quality control systems that provide feedback for process correction.Mainstream Engineering has developed, built and evaluated an in-line optical scanner based inspection system with the capability to determine membrane thickness, identify defects, and measure catalyst variability and loading. The inspection system samples the entire surface so that defects in the materials can be identified and selectively removed prior to assembly. We have worked with our partners to characterize a wide range of membranes and catalysts types using off-line techniques including x-ray fluorescence, ion-coupled plasma optical emission spectroscopy, Raman spectroscopy, and IR thermography to identify defects and their impact on cell performance. This data was then used to build calibrations and develop in-line, automated detection algorithms that can be used during full-scale production of materials, to quantify and isolate defects at multiple stages of the production process. We have used our in-line system to characterize a variety of materials including proton exchange membrane, anion exchange membrane, fluorinated and hydrocarbon membranes, catalyst coated membranes, gas diffusion layers, and gas diffusion electrodes in a variety of configurations and chemistries. This process can be rapidly adapted and applied to new materials and processing approaches as they are developed in the future order to help reduce development time in, and transition from research to production systems, as well as providing high-throughput, real-time diagnostic capability for commercial applications.

Novel High Flux Poly(m-phenylene isophtalamide)/TiO2 Membranes for Ultrafiltration with Enhanced Antifouling Performance

Wide application of ultrafiltration in different industrial fields requires the development of new membranes with tailored properties and good antifouling stability. This study is devoted to the improvement of ultrafiltration properties of poly(m-phenylene isophtalamide) (PA) membranes by modification with titanium oxide (TiO2) particles. The introduction of TiO2 particles improved membrane separation performance and increased antifouling stability and cleaning ability under UV irradiation. The developed membranes were characterized by scanning electron and atomic force microscopy methods, the measurements of water contact angle, and total porosimetry. The transport properties of the PA and PA/TiO2 membranes were tested in ultrafiltration of industrially important feeds: coolant lubricant (cutting fluid) emulsion (5 wt.% in water) and bovine serum albumin (BSA) solution (0.5 wt.%). The PA/TiO2 (0.3 wt.%) membrane was found to possess optimal transport characteristics in ultrafiltration of coolant lubricant emulsion due to the highest pure water and coolant lubricant fluxes (1146 and 32 L/(m2 h), respectively), rejection coefficient (100%), and flux recovery ratio (84%). Furthermore, this membrane featured improved ability of surface contamination degradation after UV irradiation in prolonged ultrafiltration of BSA, demonstrating a high flux recovery ratio (89–94%).

A planned review on designing of high-performance nanocomposite nanofiltration membranes for pollutants removal from water

The shortage of clean water sources and increase of demand for fresh water have become as major global challenges not only in industries but also inhuman life. Meanwhile, membrane technology has been extensively noticed due to high separation efficiency, energy-saving and environmentally-friendly characteristic. So, development of new membrane is a vital step in advancing of membrane application in water-treatment. This paper presents a comprehensive review on development of high-performance nanofiltration membrane based on nanotechnology for wastewater treatment. Application of new nanomaterials has enabled fabrication of NF-membranes with improved separation properties for pollutants removal from water. Recognizing that conventional membranes are not necessarily suitable for industrial applications and/or process intensifications many attempts were made recently to use of nanomaterials into NF-membranes, aiming to overcome trade-off relationship between flux/selectivity and to improve their stability. So, development of new structured nanomaterial with desirable properties is one of most crucial research topics for membrane researchers. Accordingly, an overview on different methods to design of advanced nanomaterial presented that allow us to overcome their inherent problems in membranes fabrication such as agglomeration, defects formation, insufficient pores’ tuning, poor active sites and anti-fouling properties; however, selection of appropriate nanomaterials is a challenge of utmost difficulty. Various types of nanomaterials such as zeolites, carbon based, framework (MOF/ZIF/COF), nano-biopolymers and special nanoparticles such as SFNPs, SFNCs, POSS, ZCPs, and nickel hydroxide nanosheet are presented and their roles in NF-transport are discussed as well as strategies for surface modification of nanoparticles to promoting their surface charges density. Moreover, fabrication methods of nano enhanced NF-membranes including layer by layer assembly, hollow fiber spinning, electrospinning of nanofibers, construction of thin-film nanocomposite besides blending, co-polymerization; cross-linking and grafting techniques are discussed. A proper view for selection of appropriate nanoparticles in membrane fabrication is offered while considering types of pollutants to be removed.

Anti-poisoned oxygen reduction by the interface modulated Pd@NiO core@shell

The methanol (CH3OH) crossover in direct methanol fuel cells is very poisonous to cathodic noble metal electrocatalysts, which usually leads to serious degradation of electrocatalytic performance. However, most focus of present research has been concentrated on the persistent pursuit of enhancing the sluggish ORR reactions while the pivotal methanol crossover has been left out generally. The “reactivity and anti-poison” dilemma has been approached by many surface engineering including the development of new membrane with low methanol permeability or assemble layered structures. As the notable structure-dependent performance in catalytic reaction, our work has proposed Pd@NiO core@shell as an interface engineering approach that can significantly inhibit the CO species adsorption while preserving the ORR reactivity, which can also exhibit superior stability even in poisoning circumstances. Herein, we report a series of unique Pd@NiO-x/C with controlled interface structure to overcome the activity and anti-poisoning issues of oxygen reduction reaction (ORR), where the optimized Pd@NiO/C exhibits a high activity of 0.24 A mg−1, excellent tolerance over the CH3OH/CO poisoning as well as superior stability even in the practical poisoning circumstances, all which are far better than the commercial Pt/C and Pd/C. DFT calculations reveal that the excellent ORR performance with effective methanol tolerance become superior with core@shell interfacial engineering. With effective modulations, the generalized interfacial d-band-offset can be achieved for counteracting the ORR barriers with extra-high current density. The simultaneously high activity and excellent anti-poisoning features of the Pd@NiO nanostructure make it a practically potential electrocatalyst for fuel cell and beyond.

A molecular simulation protocol for swelling and organic solvent nanofiltration of polymer membranes

Polymer membranes have received considerable interest for organic solvent nanofiltration (OSN). The OSN performance is governed by many complex factors and quantitative understanding is experimentally challenging. In addition, it is a prerequisite to characterize membrane swelling in solvents prior to nanofiltration. A molecular simulation protocol is developed herein to investigate the swelling of three polymer membranes namely polybenzimidazole (PBI), polyimide (PI) and polymer of intrinsic microporosity (PIM-1) in four organic solvents (methanol, ethanol, acetonitrile and acetone), and then examine the OSN through the swollen membranes. The simulation protocol can highly efficiently simulate membrane swelling, which is approximately one order of magnitude faster than normal simulation method. The predicted swelling degrees of the three polymer membranes follow experimentally measured trend, exhibit good relationships with the polymer-solvent solubility parameter differences and the mean pore sizes of swollen membranes. For the OSN of a dye (methylene blue) in the four organic solvents, 100% rejection is found by the swollen PBI, PI and PIM-1 membranes. The predicted solvent permeabilities through PIM-1 and PI membranes match fairly well with experimental data, and their dependences on solvent viscosity, pore size and polymer-solvent interaction are examined. From this simulation study, the microscopic insights into the swelling of polymer membranes and the permeation of organic solvents are provided, which are useful for the development of new membranes for high-performance OSN.

Vanadium redox flow battery with slotted porous electrodes and automatic rebalancing demonstrated on a 1 kW system level

Capacity loss due to electrolyte crossover through the membrane and pump losses due to pressure drop at the porous electrodes are widely known issues in vanadium redox flow batteries during operation. In commercial systems, these losses account for a significant reduction in the overall efficiency. Previous studies have been focused on the development of new membranes to solve the capacity loss, and design modification to reduce the pressure drop. In this work, we propose unique solutions to solve both problems and are demonstrated in a multi-cell stack for the first time. A 20-cell, 1 kW vanadium redox flow battery stack was assembled using thin bipolar plates and porous electrodes featuring interdigitated flow channels. Such a stack design is novel of its kind and can mitigate various problems associated with flow distribution and pump power in flow batteries. In addition, the electrolyte tanks were shunted together to rebalance the electrolyte automatically. The stack showed a very good and stable performance with an energy efficiency of 80.5% at a current density of 80 mA cm−2. The use of hydraulic shunt resulted in a constant capacity over 250 cycles while the use of flow channels on the porous electrodes resulted in ∼40% reduction in pressure drop, compared to a stack with standard felts. The reduction in pressure drop by employing flow channels reduced the pump power proportionally. Overall, capacity retention and utilization of active materials have been improved substantially. These methods are simple and applicable to any size of vanadium redox flow battery.

Solvent nanofiltration through polybenzimidazole membranes: Unravelling the role of pore size from molecular simulations

There has been considerable interest in the use of polymer membranes for solvent nanofiltration. While the pore size of nanofiltration membranes is generally known to be within 0.5–2 nm, the precise control of pore size and quantitative understanding of the role of pore size are experimentally challenging. By molecular simulations, in this study, we investigate solvent nanofiltration through polybenzimidazole (PBI) membranes with different pore sizes. Five PBI model membranes are constructed and pretreated by methanol, with the mean pore size (MPZ) ranging from 3.53 to 6.38 Å. When the MPZ increases, large pores are more populated and connected in the membrane. It is revealed that methanol permeation is governed by the presence and interconnectivity of large pores. For the membrane with a MPZ of 6.38 Å, the permeation of methanol and water is simulated. Compared with methanol, water permeation is faster but slowed down at a later stage due to membrane compression. The rejection of a model solute, glucose, is found to be 100%. This simulation study highlights the crucial role of pore size, as well as pretreatment, in solvent permeation, and would facilitate the development of new membranes for high-performance solvent nanofiltration.

Preparation of poly (N,N‐dimethylaminoethyl methacrylate) (PDAEM) membranes: Application for water purification

ABSTRACTThe present work concerns a development of new membranes for performing ions separation. These membranes were prepared by solution casting followed by solvent evaporation, using a commercial cellulose triacetate (CTA), synthesized poly (N,N‐dimethylaminoethyl methacrylate), macrocylic polyethers (15‐crown‐5 and Dibenzo‐24‐crown‐8) as carrier and dioctylphtalate as plasticizer. Different Polymer Inclusion Membranes were characterized using physical and chemical techniques as well as Fourier transform infrared, thermogravimetric analysis, and scanning electron microscopy. Transport of lead and cadmium in aqueous solution has been studied using these systems. The selective separation of these membranes is accomplished by the presence of specific compounds, called carriers, in the membrane phase. The carriers are responsible to facilitate the transport of the target component across selective membranes. The influence of the membrane nature has been studied using some supports of different physical characteristics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46592.

Tubular ultrafiltration ceramic membrane based on titania nanoparticles immobilized on macroporous clay-alumina support: Elaboration, characterization and application to dye removal

Abstract The development of new membranes with improved separation properties, high mechanical and thermal stability using inexpensive and naturally abundant materials is of utmost importance for sustainable development and environmental applications. Ceramic materials due to their high chemical, mechanical and thermal stability in combination to their facile surface functionalization have inspired material scientists to design innovative low-cost ceramic-based membrane supports. This study focuses on the preparation and characterization of novel asymmetric ultrafiltration ceramic membrane coated with single separation layer made of TiO2 nanoparticles, and its application to removal of alizarin dye from aqueous solutions. The membrane was prepared by a simple and one-step deposition of micrometer-thick titania layer on the internal surface of the tubular-shape porous clay-alumina membrane support from an aqueous colloidal suspension of titanium oxide (TiO2) nanoparticles with size of 10 nm. The colloidal suspension was prepared in the presence of 0.2 wt.% of Dolapix, and 30 g of an aqueous solution of polyvinyl alcohol at 12 wt.% and 66 mL of H2O. Microfiltration tubular supports of 10 mm/7 mm (outer/inner diameter) were prepared through an extrusion method followed by a sintering process using China Clay Rajmahal grade and alumina, as mineral precursors. The composition of 25% of clay and 75% of alumina was selected in this work as it showed a lower sintering temperature (Tf = 1350 °C) which could ensure low cost elaboration process, an average water flux of 850 L h−1 m−2 bar−1 as well as enhanced mechanical performance (≈37 MPa) and large porosity (48%) with an average pore diameter of 0.75 µm. SEM characterization showed that at the sintering temperature of 800 °C, the TiO2 nanoparticles coated densely and homogeneously the ceramic support forming a thin layer of about 4.2 µm in thickness and leading to a clear reduction of the mean pore size (50 nm approximatively) while providing a water permeability of 117 L h−1 m−2 bar−1. The so-designed ultrafiltration (UF) tubular ceramic membrane has proved efficient for alizarin red dye removal with a retention rate of 99% and a permeate flux of 70 L h−1 m−2 at pH 9 and a transmembrane pressure of 5 bar.

How To Optimize the Membrane Properties for Membrane Distillation: A Review

Membrane distillation (MD) uses a microporous hydrophobic membrane to separate dissolved molecules from a liquid stream. Notwithstanding the great potential, membrane distillation is not applied on an industrial level yet, because of the lack of specifically developed membranes, modules, and techno-economic data at full scale. This review gives a comprehensive overview of the optimal membrane properties and can serve as a guideline for the development of new membranes, specifically for membrane distillation. Optimization of the membrane is needed to sufficiently resist wetting. Generally, a pore diameter of 0.3 μm is recommended to balance between a high liquid entry pressure and flux. Since vacuum membrane distillation is more sensitive to wetting, a smaller pore diameter could be appropriate for this configuration to avoid membrane wetting. An optimal membrane thickness is found between 10 and 700 μm, depending on process conditions, balancing between mass transport and energy loss. To improve the mass transfer and energy efficiency, membrane porosity should preferably be as high as possible (>75%), while low tortuosity (1.1–1.2) and thermal conductivity (>0.06 w·m–1·K–1) are recommended as well.

Sipn Systems Used As Membranes for Fuel Cell

SIPN systems used as membranes for fuel cell. The development of new membranes in order to replacement of Nafion ®, with greater thermal stability, chemical, electrochemical, and high conductivity is one of the key to reducing the manufacturing costs of PEMFC. Many studies were found in literature working with composites and nanocomposites based on Nafion®, which does not eliminate the polymer dependence [1]. Several studies involve commercial polymers sulfonation [2] and others employ basic polymers, among them poliimidazol and polibenzimidazol [3]. From these basic polymers are formulated complexes with strong acids, particularly H3PO4, which act as a source of protons to membrane charge transport. New polymeric materials have been explored, such as interpenetrating polymer networks (IPN) [4]. Using this semi-IPN systems allow to control the free volume and dimensional mechanical stability. The semi-IPN (SIPN) is defined as “a polymer comprising one or more networks linear or branched polymer(s) characterized by the penetration on a molecular scale of at least one of the networks by at least some of the linear or branched macromolecule [5]. In current work the SIPN are based in monomer diglycidyl ether of bisphenol A (DGEBA), using curing agent4,4' diaminodiphenyl-sulphone (DDS) and the linear polymer polyethyleneimine (PEI) as described in previous work by Loureiro [6]. The membrane SIPN 47% of PEI was doped with phosphoric acid in varying concentrations in 5, 10 and 15, 20 and 30% (w/w). For comparison the same sample was sulfonated (SIPN47-SO3H) procedure adapted from Rocco et.al. [7] by employing nominal degree of sulfonation of 1:4, 1:2, 1:1 and 2:1. After the sulfonation procedure, membranes were kept in a desiccator under vacuum. Samples are sulfonated at different ratios and were characterized by FTIR, TGA, DSC and Electrochemical Impedance Spectroscopy (EIS). The thermal study by TGA and DSC to the SIPN47 show the high stability of membrane. The TGA and DTG curves evidence an initial weight loss at approximately 80-85oC, associated with elimination of adsorbed water. SIPN membrane exhibited 5.2 % weight losses, indicating the amount of water retained in the samples. Since the samples were dried prior to the analysis, the amount of water eliminated was probably rapidly adsorbed during the sample handling, evidencing a highly hygroscopic behavior. SIPN samples degradation starts at approximately 280oC, which corresponds to the decomposition temperature. The SIPN membranes exhibit water elimination in a broad temperature range, up to 200oC. This is a very promising characteristic of the studied system, since water retention above 100 oC is one of the limiting features of polymer membranes for fuel cells, which, operating at temperatures higher than 120 oC, avoid the catalyst poisoning by CO. The DSC study show the higher stability of SIPN sample, which show one only Tg at 67oC, and there aren’t another behavior of degradation, in order the only one Tg indicates that the system produced is fully miscible. The Impedance study show the dependence of the conductivity with higher values of acid doped achieving high proton conductivity values 8,29x10-2W-1cm-1 at 80oC. On the other hand sulfonated SIPN samples do not show the same behavior, there aren’t significant increase with increasing degrees of sulfonated in the SIPN samples. Table I and II lists the conductivity values at 20 and 80 oC, as well as log(A0) and activation energy values for the SIPN/H3PO4 and SIPN-SO3H membranes at differents sulfonated degrees. Table I: Conductivity, log(A0) and activation energy values obtained for IPN/H3PO4 membranes. Table II: Conductivity, log(A0) and activation energy values obtained for IPN-SO3H membranes. The conductivity increase with the temperature is a consequence of different factors, including: higher mobility of water molecules, higher acid dissociation and homogenization of the membranes nanostructure, which allows the proton transport among different hydrated nanodomains inside the membrane. The high thermal stability exhibited by the SIPN membranes, above 270oC, is sufficient for their application in PEMFC for intermediate temperature operation and the SIPN produce is fully miscible. The membranes doped with H3PO4 at 20% shows higher values of conductivity 0,08 W-1cm-1 than the best sulfonated sample degree 10-3 W-1cm-1.

Challenges and Progress in Membranes, Catalysts, and Meas for PEM Water Electrolysis

In a world in which fossil fuel energy is becoming ever more scarce and expensive and countries are struggling to meet their carbon reduction obligations, hydrogen solutions have finally reached the top of energy agendas. The only industrially applicable zero carbon method to produce hydrogen is via electrolysis utilizing renewable sources of electricity. ITM Power is at the very heart of the initiatives and programmes to adopt hydrogen technology that will reduce both carbon footprints and energy costs. Using its technology and knowhow, ITM is aiming to be the world leading supplier of both infrastructure for the production of green hydrogen transport fuel, and products for the generation and storage of hydrogen fuel from internittent renewable energy sources. Despite having a number of electrolyser products on the market, ITM Power have an active PEM electrolyser research and development programme aimed at the next generation of electrolysers. Some of the electrochemical and materials challenges faced by both ITM and the industry will be presented along with recent results, examples given below. PEM electrolysers have a lifetime of 5-10 years; as such there is difficulty in getting new materials to market. ITM along with the National Physical Laboratory have used a novel in-situ reference electrode to help understand catalyst degradation within the cell. This approach enables separation of the relative contributions of anode and cathode to the overall reaction. During shut down periods it was observed for the first time that the cathode contributes more to changes in the open circuit voltage. This knowledge has been used to show that the majority of the degradation is occurring on the cathode catalyst, which is in contrast to the perceived thought which assumes the anode degrades faster. Changes in the electrochemically active surface area of the platinum cathode as a result of potential cycling were determined in-situ via hydrogen underpotential cyclic voltammetry. Scanning electron microscopy and X-ray tomography were used to correlate changes in catalyst morphology with performance degradation of both carbon-supported and unsupported platinum catalysts. These experiments have led to the development of accelerated stress tests, based on cycling of the electrode potential, for PEM electrolyser catalysts. In addition ITM have made progress in the development of new membranes for PEM electrolysis. ITM’s approach to membrane development is the UV polymerisation of low cost hydrocarbon monomers. A new highly conductive membrane has been developed and tested to 3 A∙cm-2. This membrane is 125 um thick to minimise hydrogen crossover, has a conductivity of 260 mS∙cm-1 and is extremely low cost. When made into a MEA, this membrane allows a voltage of below 1.6 V at 1 A∙cm-2 at only 55°C. This has been benchmarked against Nafion(R)115.

Calcium carbonate scaling in seawater desalination by ammonia–carbon dioxide forward osmosis: Mechanism and implications

Forward osmosis (FO) is an osmotically driven membrane process, where the membrane separates a draw solution (DS) with high salinity from a feed solution (FS) with low salinity. There can be a counter direction flow of salt (i.e., salt leakage) that may interact with the water flux through the FO membrane. For the first time reported, this study describes a new calcium carbonate scaling phenomenon in the seawater FO desalination process using ammonium bicarbonate as the DS. The scaling on the membrane surface at the feed side is caused by the interaction between an anion reversely diffused from the DS and a cation present in the FS, causing a significant decline of the water flux. The composition of the scaling layer is dominated by the solubility (represented as solubility product constant, Ksp) of salt formed by the paired anion and cation. Membrane surface morphology plays a crucial role in the reversibility of the scaling. If the scaling occurs on the active layer of the FO membrane, hydraulic cleaning (increasing crossflow velocity) efficiency to restore the water flux is up to 82%. When scaling occurs on the support layer of the FO membrane, the hydraulic cleaning efficiency is strongly reduced, with only 36% of the water flux recovered. The present study reveals the risk of scaling induced by the interaction of feed solute and draw solute, which is different from the scaling caused by the supersaturation in reverse osmosis and other FO studies reported. The scaling investigated in this study can occur with a very low solute concentration at an early stage of the FO process. This finding provides an important implication for selection of draw solution and development of new membranes in the FO process.