Reinforced anion exchange membrane based on thermal cross-linking method with outstanding cell performance for reverse electrodialysis

A poly(ethylene)-reinforced anion exchange membrane based on cross-linked quaternary-aminated polystyrene and quaternary-aminated poly(phenylene oxide) was developed for reverse electrodialysis. Although reverse electrodialysis is a clean and renewable energy generation system, the low power output and high membrane cost are serious obstacles to its commercialization. Herein, to lower the membrane cost, inexpensive polystyrene and poly(phenylene oxide) were used as ionomer backbones. The ionomers were impregnated into a poly(ethylene) matrix supporter and were cross-linked in situ to enhance the mechanical and chemical properties. Pre-treatment of the porous PE matrix membrane with atmospheric plasma increased the compatibility between the ionomer and matrix membrane. The fabricated membranes showed outstanding physical, chemical, and electrochemical properties. The area resistance of the fabricated membranes (0.69–1.67 Ω cm²) was lower than that of AMV (2.58 Ω cm²). Moreover, the transport number of PErC(5)QPS-QPPO was comparable to that of AMV, despite the thinness (51 μm) of the former. The RED stack with the PErC(5)QPS-QPPO membrane provided an excellent maximum power density of 1.82 W m⁻² at a flow rate of 100 mL min⁻¹, which is 20.7% higher than that (1.50 W m⁻²) of the RED stack with the AMV membrane.

PErC(5)QPS-QPPO exhibited 20.7% higher MPD than commercial AEM (AMV).     

Performance and stability comparison of Aemion™ and Aemion+™ membranes for vanadium redox flow batteries

Anion exchange membranes (AEMs) have shown a significant rise in performance and durability within recent years for applications such as electrolysis and fuel cells. However, in vanadium redox-flow batteries, their use is of particular interest to lower costs and self-discharge rates compared to conventional perfluorinated sulfonic acid-based ionomers such as Nafion. In this work we evaluate the properties of two commercial AEMs, Aemion™ and Aemion+™, based on ex situ characterizations, an accelerated stress test degradation study (>1000 hours storage in highly oxidizing VO₂⁺ electrolyte at 35 °C) and electrochemical battery cycle tests. All membranes feature low ionic resistances of below 320 mΩ cm², enabling battery cycling at 100 mA cm⁻². Aemion shows considerable VO²⁺ formation within a VO₂⁺ stress test, whereas Aemion+ remains almost unaffected in the 1058 h stress test. Evaluating self-discharge data, cycling performance and durability data, Aemion+™ (50 μm thickness) features the best properties for vanadium redox-flow battery operation.

Cycling behaviour of Aemion™ (50 μm), Aemion+™ (50 μm), Aemion+™ (15 μm) and Nafion® 212 (50 μm) at 100 mA cm⁻². (a) Coulombic efficiency, (b) energy efficiency and (c) membrane resistance.     

Fabrication of a composite anion exchange membrane with aligned ion channels for a high-performance non-aqueous vanadium redox flow battery

Fabrication of high-conductivity ion exchange membranes (IEMs) is crucial to improve the performance of non-aqueous vanadium redox flow batteries (NAVRFBs). In the present work, anion exchange membranes with high-conductivity were fabricated by aligning ion channels of the polymer electrolyte impregnated in porous polytetrafluoroethylene (PTFE) under electric fields. It was observed that the ion channels of the polymer electrolyte were uniformly orientated in the atomic-force microscopy image. Its morphological change could minimize detouring of the transport of BF₄⁻ ions. The results showed through-plane conductivity was improved from 12.7 to 33.1 mS cm⁻¹. The dimensional properties of the fabricated membranes were also enhanced compared with its cast membrane owing to the reinforcing effect of the substrate. Especially, the NAVRFB assembled with the optimized membrane showed increased capacities, with a 97% coulombic efficiency and 70% energy efficiency at 80 mA cm⁻². Furthermore, the optimized membrane made it possible to operate the NAVRFB at 120 mA cm⁻². Its operating current density was 120 times higher than that of a frequently used AHA membrane for RFBs.

Fabrication of high-conductivity ion exchange membranes (IEMs) is crucial to improve the performance of non-aqueous vanadium redox flow batteries (NAVRFBs).     

Thin robust Pd membranes for low-temperature application

It is known that hydrogen embrittlement could result in warping and destruction of pure Pd membranes, which limits the working temperatures to be above 293 °C. This study attempted to investigate the relationship between hydrogen embrittlement resistance and membrane geometry of ultrathin pure Pd membranes of 2.7–6.3 μm thickness. Thin tubular Pd membranes with an o.d. of 4 mm, 6 mm and 12 mm immediately suffered from structural destruction when exposed to H₂ at room temperature. In contrast, thin hollow fiber membranes (outer diameter, 2 mm, thickness < 4 μm) exhibit strong resistance against hydrogen embrittlement at temperatures below 100 °C during repeated heating/cooling cycles at a rate up to 10 °C min⁻¹ under H₂ atmosphere. This is ascribed to reduced lattice strain gradients during α–β phase transition in cylindrical structures and lower residual stresses according to in situ XRD analysis, which shows a great prospect in low temperature applications.

Thin tubular membranes (outer diameter, 2 mm, thickness < 4 mm) exhibits strong resistance against hydrogen embrittlement at temperatures below 100 °C due to reduced lattice strain gradients in cylindrical structures and lower residual stresses.     

Polybenzimidazole/Nafion hybrid membrane with improved chemical stability for vanadium redox flow battery application

In order to increase the chemical stability of polybenzimidazole (PBI) membrane against the highly oxidizing environment of a vanadium redox flow battery (VRFB), PBI/Nafion hybrid membrane was developed by spray coating a Nafion ionomer onto one surface of the PBI membrane. The acid–base interaction between the sulfonic acid of the Nafion and the benzimidazole of the PBI created a stable interfacial adhesion between the Nafion layer and the PBI layer. The hybrid membrane showed an area resistance of 0.269 Ω cm² and a very low vanadium permeability of 1.95 × 10⁻⁹ cm² min⁻¹. The Nafion layer protected the PBI from chemical degradation under accelerated oxidizing conditions of 1 M VO₂⁺/5 M H₂SO₄, and this was subsequently examined in spectroscopic analysis. In the VRFB single cell performance test, the cell with the hybrid membrane showed better energy efficiency than the Nafion cell with 92.66% at 40 mA cm⁻² and 78.1% at 100 mA cm⁻² with no delamination observed between the Nafion layer and the PBI layer after the test was completed.

Novel polybenzimidazole (PBI)/Nafion hybrid membranes for the VRFB are made by spray coating a Nafion layer to protect PBI from chemical degradation.     

Pt-grown carbon nanofibers for detection of hydrogen peroxide

Removal of left-over catalyst particles from carbon nanomaterials is a significant scientific and technological problem. Here, we present the physical and electrochemical study of application-specific carbon nanofibers grown from Pt-catalyst layers. The use of Pt catalyst removes the requirement for any cleaning procedure as the remaining catalyst particles have a specific role in the end-application. Despite the relatively small amount of Pt in the samples (7.0 ± 0.2%), they show electrochemical features closely resembling those of polycrystalline Pt. In O₂-containing environment, the material shows two separate linear ranges for hydrogen peroxide reduction: 1–100 μM and 100–1000 μM with sensitivities of 0.432 μA μM⁻¹ cm⁻² and 0.257 μA μM⁻¹ cm⁻², respectively, with a 0.21 μM limit of detection. In deaerated solution, there is only one linear range with sensitivity 0.244 μA μM⁻¹ cm⁻² and 0.22 μM limit of detection. We suggest that the high sensitivity between 1 μM and 100 μM in solutions where O₂ is present is due to oxygen reduction reaction occurring on the CNFs producing a small additional cathodic contribution to the measured current. This has important implications when Pt-containing sensors are utilized to detect hydrogen peroxide reduction in biological, O₂-containing environment.

Application specific Pt-grown carbon nanofibers for H₂O₂ detection were characterized and the roles of dissolved oxygen and chloride ions on the electrochemical performance were assessed in detail.     

3D Pd/Co core–shell nanoneedle arrays as a high-performance cathode catalyst layer for AAEMFCs

A novel cathode architecture using vertically aligned Co nanoneedle arrays as an ordered support for application in alkaline anion-exchange membrane fuel cells (AAEMFCs) has been developed. The Co nanoneedle arrays were directly grown on a stainless steel sheet via a hydrothermal reaction and then a Pd layer was deposited on the surface of the Co nanoneedle arrays using a vacuum sputter-deposition method to form Pd/Co nanoneedle arrays. After transferring the Pd/Co nanoneedle arrays to an AAEM, a cathode catalyst layer was formed. Without the use of an alkaline ionomer, the AAEMFC with the prepared cathode catalyst layer showed an enhanced performance with ultra-low Pd loading of down to 33.5 μg cm⁻², which is much higher than the conventionally used cathode electrode with a Pt loading of 100 μg cm⁻². This is the first report where three-dimensional Co nanoneedle arrays have been used as the cathode support in an AAEMFC, which is able to deliver a higher power density without an alkaline ionomer than that of conventional membrane electrode assembly (MEA).

A novel ordered Pd/Co nanoneedle array was used as a cathode in an AAEMFC and delivered a higher power density than that of conventional MEA.     

Ladder-type sulfonated poly(arylene perfluoroalkylene)s for high performance proton exchange membrane fuel cells

Sulfonated poly(arylene perfluoroalkylene)s containing a sulfone-bonded ladder structure (SPAF-P-Lad) were synthesized by treating the precursor SPAF-P polymers with oleum as a novel proton exchange membrane for fuel cells. SPAF-P-Lad membranes had excellent solubility in polar organic solvents and high molecular weight (M_n = 145.4–162.9 kDa, M_w = 356.9–399.1 kDa) to provide bendable membranes with ion exchange capacity (IEC) ranging from 1.76 to 2.01 meq. g⁻¹. SPAF-P-Lad membranes possessed higher proton conductivity than that of the precursor SPAF-P membranes because of the stronger water affinity. Compared with SPAF-P membranes (T_g: 72–90 °C, Young''s modulus: 0.08–0.42 GPa; yield stress: 5.7–15.1 MPa), SPAF-P-Lad membranes showed better mechanical stability to humidity and temperature and improved tensile properties (Young''s modulus: 0.51–0.59 GPa; yield stress: 23.9–29.6 MPa). The selected membrane, SPAF-mP-Lad, exhibited improved fuel cell performance, in particular, under low humidity with air; the current density at 0.5 V was 0.56 A cm⁻², while that for SPAF-pP was 0.46 A cm⁻². The SPAF-mP-Lad membrane endured an open circuit voltage hold test for 1000 h with average decay of as small as 70 μV h⁻¹. A series of post-analyses including current–voltage characteristics, molecular structure, molecular weight, and IEC suggested very minor degradation of the membrane under the accelerated testing conditions.

Sulfone-bonded ladder-type sulfonated poly(arylene perfluoroalkylene)s (SPAF-P-Lad) were synthesized by an easy method to achieve high thermo-mechanical stability, proton conductivity, fuel cell performance and remarkable in situ durability.     

Partially fluorinated copolymers containing pendant piperidinium head groups as anion exchange membranes for alkaline fuel cells

A new series of partially fluorinated copolymers with varying alkyl side chain length (C3, C6 and C9) and piperidinium head groups have been synthesized and characterized in detail in an effort to improve membrane properties for alkaline fuel cell applications. The copolymers (QPAF4-Cx-pip) provided thin and bendable membranes by solution casting, and achieved high hydroxide ion conductivity up to 97 mS cm⁻¹ in water at 80 °C. Membrane properties such as water absorbability, conductivity, and mechanical properties were tunable with the side chain length. The copolymer main chain and the piperidinium groups were both alkaline stable and the membranes retained high conductivity in 4 M KOH at 80 °C for as long as 1000 h, however, conductivity was lost in 8 M KOH due to Hofmann degradation of the side chain. QPAF4-C3-pip copolymer with the best-balanced properties as anion exchange membrane functioned well in a hydrogen/oxygen alkaline fuel cell to achieve 226 mW cm⁻² peak power density at 502 mA cm⁻² current density under fully humidified conditions with no back pressure.

Piperidinium functionalized partially fluorinated copolymers with varying alkyl spacer length were synthesized and evaluated as anion exchange membranes to achieve improved performance in alkaline fuel cells.     

Solid oxide fuel cell with a spin-coated yttria stabilized zirconia/gadolinia doped ceria bi-layer electrolyte

A thin yttria stabilized zirconia (YSZ)/gadolinia doped ceria (GDC) bi-layer membrane is fabricated through the slurry spin coating technique and used as an electrolyte of a solid oxide fuel cell with La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ as the cathode. The viscosity of the YSZ slurry is controlled by adding ethanol in the terpineol solvent, which shows a negligible effect on the thickness but a remarkable influence on the porosity of the YSZ film. The thickness of the YSZ layer increases with the YSZ content in the slurry. The YSZ films are pre-sintered at various temperatures, and the one sintered at 1200 °C has a moderate interaction with the GDC slurry, forming a 10 μm-thick YSZ/GDC bilayer with a low porosity and a low ohmic resistance. The corresponding single cell shows a maximum power density of 1480 mW cm⁻² at 750 °C.

Thin YSZ/GDC bi-layer electrolyte is prepared with the slurry spin coating method for SOFCs, and shows a P_max of 1480 mW cm⁻² at 750 °C.     

Water management in anion-exchange membrane water electrolyzers under dry cathode operation

Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers to minimize contamination of the generated hydrogen. However, water management under such operation conditions makes it challenging to maintain reliable performance and durability. Here, we utilize high-resolution in situ neutron imaging (∼6 μm effective resolution) to analyze the water content inside the membrane-electrode-assembly of an anion-exchange membrane water electrolyzer. The ion-exchange capacity (IEC) and thus hydrophilicity of the polymer binder in the cathode catalyst layer is varied to study the influence on water content in the anode (mid IEC, 1.8–2.2 meq. g⁻¹ and high IEC, 2.3–2.6 meq. g⁻¹). The neutron radiographies show that a higher ion-exchange capacity binder allows improved water retention, which reduces the drying-out of the cathode at high current densities. Electrochemical measurements confirm a generally better efficiency for a high IEC cell above 600 mA cm⁻². At 1.5 A cm⁻² the high IEC has a 100 mV lower overpotential (2.1 V vs. 2.2 V) and a lower high frequency resistance (210 mΩ cm⁻²vs. 255 mΩ cm⁻²), which is believed to be linked to the improved cathode water retention and membrane humidification. As a consequence, the performance stability of the high IEC cell at 1 A cm⁻² is also significantly better than that of the mid IEC cell (45 mV h⁻¹vs. 75 mV h⁻¹).

Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers, but water management is crucial. This is visualized using high-resolution neutron radiography and the ion-exchange capacity of the cathode ionomer is varied.     

Sulfonated graphene oxide/Nafion composite membranes for high temperature and low humidity proton exchange membrane fuel cells

Iron oxide (Fe₃O₄) nanoparticles anchored over sulfonated graphene oxide (SGO) and Nafion/Fe₃O₄–SGO composites were fabricated and applied as potential proton exchange membranes in proton exchange membrane fuel cells (PEMFCs) operated at high temperature and low humidity. Fe₃O₄ nanoparticles bridge SGO and Nafion through electrostatic interaction/hydrogen bonding and increased the intrinsic thermal and mechanical stabilities of Nafion/Fe₃O₄–SGO composite membranes. Nafion/Fe₃O₄–SGO composite membranes increased the compactness of ionic domains and enhanced the water absorption and proton conductivity while restricting hydrogen permeability across the membranes. The proton conductivity of Nafion/Fe₃O₄–SGO (3 wt%) composite membrane at 120 °C under 20% relative humidity (RH) was 11.62 mS cm⁻¹, which is 4.74 fold higher than that of a pristine recast Nafion membrane. PEMFC containing the Nafion/Fe₃O₄–SGO composite membrane delivered a peak power density of 258.82 mW cm⁻² at a load current density of 640.73 mA cm⁻² while operating at 120 °C under 25% RH and ambient pressure. In contrast, under identical operating conditions, a peak power density of only 144.89 mW cm⁻² was achieved with the pristine recast Nafion membrane at a load current density of 431.36 mA cm⁻². Thus, Nafion/Fe₃O₄–SGO composite membranes can be used to address various critical problems associated with commercial Nafion membranes in PEMFC applications.

Preparation process of Nafion/Fe₃O₄–SGO composite membranes.     

Surface hemocompatible modification of polysulfone membrane via covalently grafting acrylic acid and sulfonated hydroxypropyl chitosan

In this study, acrylic acid (AA) and sulfonated hydroxypropyl chitosan (SHPCS) were covalently grafted on the PSf membrane surface to improve its hemocompatibility. First, the modified AA-PSf membrane was obtained through the Friedel–Craft reaction between acrylic acid and the PSf membrane surface. Then, the modified SHPCS-AA-PSf membrane was prepared by grafting SHPCS onto the AA-PSf membrane surface via the dehydration acylation of the carboxyl group of the AA-PSf membrane with the amino group of SHPCS. ATR-FTIR and XPS measurements confirmed that the –COOH group and SHPCS were successfully grafted onto the surface of the PSf membrane. The modified PSf membranes showed suppressed platelet adhesion and lower protein adsorption (161 μg cm⁻²) compared with the pristine PSf membrane (341 μg cm⁻²). Hemocompatibility testing showed that modified membrane materials had a prolonged clotting time, plasma recalcification time (PRT), activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT). All of these results indicated that the surface modification of the PSf membrane with acrylic acid and SHPCS had good hemocompatibility and anticoagulant property.

In this study, acrylic acid (AA) and sulfonated hydroxypropyl chitosan (SHPCS) were covalently grafted on the PSf membrane surface to improve its hemocompatibility.     

Uncovering the origin of enhanced field emission properties of rGO–MnO2 heterostructures: a synergistic experimental and computational investigation

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices. Herein, we report the synthesis of MnO₂ nanorods and a rGO/MnO₂ nano-heterostructure using low-cost hydrothermal and modified Hummers'' methods, respectively. Detailed characterization and confirmation of the structural and morphological properties are done via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Compared to the isolated MnO₂ nanorods, the rGO/MnO₂ nano-heterostructure exhibits impressive field emission (FE) performance in terms of the low turn-on field of 1.4 V μm⁻¹ for an emission current density of 10 μA cm⁻² and a high current density of 600 μA cm⁻² at a relatively very low applied electric field of 3.1 V μm⁻¹. The isolated MnO₂ nanorods display a high turn-on field of 7.1 for an emission current density of 10 μA cm⁻² and a low current density of 221 μA cm⁻² at an applied field of 8.1 V μm⁻¹. Besides the superior FE characteristics of the rGO/MnO₂ nano-heterostructure, the emission current remains quite stable over the continuous 2 h period of measurement. The improvement of the FE characteristics of the rGO/MnO₂ nano-heterostructure can be ascribed to the nanometric features and the lower work function (6.01 and 6.12 eV for the rGO with 8% and 16% oxygen content) compared to the isolated α-MnO₂(100) surface (Φ = 7.22 eV) as predicted from complementary first-principles electronic structure calculations based on density functional theory (DFT) methods. These results suggest that an appropriate coupling of rGO with MnO₂ nanorods would have a synergistic effect of lowering the electronic work function, resulting in a beneficial tuning of the FE characteristics.

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices.     

MXene potassium titanate nanowire/sulfonated polyether ether ketone (SPEEK) hybrid composite proton exchange membrane for photocatalytic water splitting

A cross-linked sulfonated polyether ether ketone (C-SPEEK) was incorporated with MXene/potassium titanate nanowire (MKT-NW) as a filler and applied as a proton exchange membrane for photocatalytic water splitting. The prepared hybrid composite PEM had proton conductivity of 0.0097 S cm⁻¹ at room temperature with an ion exchange capacity of 1.88 meq g⁻¹. The hybrid composite proton exchange membrane is a reactive membrane which was able to generate hydrogen gas under UV light irradiation. The efficiency of hydrogen gas production was 0.185066 μmol within 5 h for 12% wt of MKT-NW loading. The results indicated that the MKT-NW/C-SPEEK membrane is a promising candidate for ion exchange with hydrogen gas evolution in photocatalytic water splitting and could be applied as a renewable source of energy to use in various fields of applications.

A cross-linked sulfonated polyether ether ketone (C-SPEEK) was incorporated with MXene/potassium titanate nanowire (MKT-NW) as a filler and applied as a proton exchange membrane for photocatalytic water splitting.     

Preparation and mechanism analysis of high performance ceramic membrane by spray coating

A spray coating method was proposed to fabricate an α-Al₂O₃ micro-filtration membrane with excellent performance. It was observed that air gaps could form inside the support during the coating stage that effectively prevent membrane forming particles from penetrating into the support without an intermediate layer. Thus the pure water permeability of the membrane with average pore size of 0.13 μm and thickness of 25.46 μm could reach 2893 Lm⁻² h⁻¹ bar⁻¹. The effects of firing conditions, membrane thickness and backwash or backpulse conditions on the pore size distribution of the membrane were investigated. Meanwhile the prepared membrane could sustain good filtration performance and mechanical integrity during backpulsing and backwashing processes under the transmembrane pressure (TMP) of 8 bar, which also exhibited a rejection rate of 98.8% for the carbon ink with an average particle size of 164 nm.

We have fabricated a high performance ceramic membrane. We find and explain the effect of reducing particle penetration by spray coating.     

The role of particulate matter in reduced visibility and anionic composition of winter fog: a case study for Amritsar city

Severe fog events during winter months in India are a serious concern due to the higher incidence of road accidents, flight delays and increased occurrence of respiratory diseases. The present paper is an attempt to study the twenty fog samples collected from the rooftop of an academic building of Guru Nanak Dev University, Amritsar, India from November 2017 to January 2018. Fog samples were analysed for various parameters viz. pH, electrical conductivity (EC), chloride (Cl⁻), nitrate (NO₃⁻) and sulphate (SO₄²⁻) levels. The pH, EC, and Cl⁻, NO₃⁻ and SO₄²⁻ levels in the fog samples were estimated as 6.3–7.9, 240–790 μS cm⁻¹, 108–2025 μeq L⁻¹, 105–836 μeq L⁻¹ and 822–5642 μeq L⁻¹, respectively. It was noticed that sulphate was the dominant anion in fog samples. The SO₄²⁻ to NO₃⁻ molar ratio in the fog was estimated as 7.6 which suggests the burning of fossil fuel as the major pollutant from vehicular exhausts. Multiple regression analysis was performed to evaluate the effect of PM_2.5/PM₁₀ ratio and relative humidity (RH) on visibility. A box-cox plot of power transformation produced better model fitting, employing a square root transformation of the visibility which indicated that the PM_2.5/PM₁₀ and RH have an exponential effect on visibility.

Severe fog events during winter months in India are a serious concern due to the higher incidence of road accidents, flight delays and increased occurrence of respiratory diseases.     

Performance study of μDMFC with foamed metal cathode current collector

Micro Direct Methanol Fuel Cells (μDMFCs) often have application in moveable power due to their green and portable nature. In a μDMFC''s structure, a current collector of the μDMFC needs to have high corrosion resistance such that the μDMFC can work for a long time in a redox reaction and respond to variable environmental conditions. To this end, four cathode current collectors were prepared. The materials selected were foam stainless steel (FSS) and foam titanium (FT), with fields of hole type and grid type. The performance of μDMFC with different cathode collector types was investigated by I–V–P polarization curves, Electrochemical Impedance Spectroscopy (EIS), and discharge test. The experimental results show that the maximum power density of the hole-type FSS cathode current collector μDMFC (HFSS-μDMFC) is 49.53 mW cm⁻² at 70 °C in the methanol solution of 1 mol L⁻¹, which is 70.15% higher than that of the hole-type FT cathode current collector μDMFC (HFT-μDMFC). The maximum power density of the grid-type FSS cathode current collector μDMFC (GFSS-μDMFC) is 22.60 mW cm⁻², which is 11.99% higher than that of the grid-type FT cathode current collector μDMFC (GFT-μDMFC). The performance of the HFSS-μDMFC is optimal in the methanol solution of 1 mol L⁻¹.

Micro Direct Methanol Fuel Cells (μDMFCs) often have application in moveable power due to their green and portable nature.     

Design of a novel poly(aryl ether nitrile)-based composite ultrafiltration membrane with improved permeability and antifouling performance using zwitterionic modified nano-silica

Zwitterionic nano-silica (SiO₂ NPs) obtained by lysine surface modification was used as a hydrophilic inorganic filler for preparing a poly(aryl ether nitrile) (PEN) nanocomposite membrane via an immersion precipitation phase inversion method. The effects of zwitterionic SiO₂ NPs addition on the morphology, separation and antifouling performance of the synthesized membranes were investigated. Zwitterionic surface modification effectively avoided the agglomeration of SiO₂ NPs. The PEN/zwitterionic SiO₂ NPs composite membranes exhibited improved porosity, equilibrium water content, hydrophilicity and permeability due to the introduction of hydrophilic SiO₂ NPs in the casting solution, and the optimal pure water flux was up to 507.2 L m⁻² h⁻¹, while the BSA rejection ratio was maintained at 97.4%. A static adsorption capacity of 72.9 μg cm⁻² and the FRR up to 85.3% in the dynamic antifouling experiment proved that the introduction of zwitterionic SiO₂ NPs inhibited irreversible fouling and enhanced the antifouling ability of the PEN membrane.

Zwitterionic nano-silica (SiO₂ NPs) obtained by lysine surface modification was used as a hydrophilic inorganic filler for preparing a poly(aryl ether nitrile) (PEN) nanocomposite membrane via an immersion precipitation phase inversion method.     

Dopamine incorporating forward osmosis membranes with enhanced selectivity and antifouling properties

A new type of polyamide thin-film composite forward osmosis (FO) membranes were prepared by controlling dopamine self-polymerization in the aqueous phase during interfacial polymerization. The as-prepared membranes were investigated by attenuated total reflection Fourier transform infrared, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, atomic force microscopy and water contact angle measurements. The influence of the dopamine self-polymerization degree with different polydopamine particle sizes on membrane morphologies and chemical properties was studied by regulating dopamine concentrations in the aqueous phase. FO performance of the membrane was evaluated under two different modes, i.e. active layer facing draw solution (AL-DS) and active layer facing feed solution (AL-FS). The optimized FO membranes achieved a doubly enhanced water flux (22.08 L m⁻² h⁻¹) compared with the control membrane without dopamine incorporation, and a half-reduced reverse salt flux (32.77 mmol m⁻² h⁻¹) with deionized water as the feed and 1 M NaCl as the draw in the AL-FS mode. The optimized FO membrane showed a significantly reduced structural parameter (176 μm) compared with the control membrane (635 μm), indicating the minimised internal concentration polarization. Moreover, the new FO membranes had less flux decline than the control membrane, suggesting the improved antifouling performance of the membrane. Incorporation of dopamine during interfacial polymerization can be an effective strategy to fabricate high-performance FO membranes with excellent antifouling properties.

Incorporation of dopamine enhanced selectivity and antifouling properties of novel TFC polyamide FO membranes.