Increases in the proton conductivity and selectivity of proton exchange membranes for direct methanol fuel cells by formation of nanocomposites having proton conducting channels

Peer reviewed: YesNRC publication: Ye

Using silica nanoparticles for modifying sulfonated poly(phthalazinone ether ketone) membrane for direct methanol fuel cell : A significant improvement on cell performance

Sulfonated poly(phthalazinone ether ketone) (sPPEK) with a degree of sulfonation of 1.23 was mixed with silica nanoparticles to form hybrid materials for using as proton exchange membranes. The nanoparticles were found homogeneously dispersed in the polymer matrix and a high 30 phr (parts per hundred resin) loading of silica nanoparticles can be achieved. The hybrid membranes exhibited improved swelling behavior, thermal stability, and mechanical properties. The methanol crossover behavior of the membrane was also depressed such that these membranes are suitable for a high methanol concentration in feed (3 M) in cell test. The membrane with 5 phr silica nanoparticles showed an open cell potential of 0.6V and an optimum power density of 52.9mWcm 122 at a current density of 264.6mAcm 122, which is better than the performance of the pristine sPPEK membrane and Nafion\uae 117.NRC publication: Ye

Low-biofouling membranes prepared by liquid-induced phase separation of the PVDF/polystyrene-b-poly (ethylene glycol) methacrylate blend

In the present work, the focus is laid on the formation, and low-biofouling properties of polyvinylidene fluoride (PVDF) membranes modified using an amphiphilic copolymer additive: polystyrene-b-poly (ethylene glycol) methacrylate (PS-b-PEGMA). PVDF was blended with PS-b-PEGMA and membranes were prepared by liquid-induced phase separation. The additive played a significant role on membrane formation, slightly decreasing surface porosity, reducing the shrinkage during phase separation, and increasing both the size and porosity of macrovoids. Owing to its numerous hydrophilic moieties, the copolymer was believed to promote solvent and nonsolvent exchanges during phase inversion. In addition, it significantly enhanced surface hydrophilicity and matrix hydration capability. Indeed, water was easily trapped by the PEGylated chains spread onto the surface and within the matrix, and then stored in the larger macrovoids. It led to an important reduction of protein adsorption, including bovine serum albumin (65%) and lysozyme (89%). Bacterial attachment tests revealed that adhesion of Escherichia coli and Staphylococcus epidermidis was almost totally prevented (over 99% reduction of attachment), which demonstrates the excellent efficiency of PS-b-PEGMA copolymer to provide PVDF membranes with low-biofouling properties

Sulfonated poly(aryl ether ether ketone ketone)s containing fluorinated moieties as proton exchange membrane materials

Peer reviewed: YesNRC publication: Ye

Antifouling pseudo-zwitterionic poly(vinylidene fluoride) membranes with efficient mixed-charge surface grafting via glow dielectric barrier discharge plasma-induced copolymerization

This work reports on the glow dielectric barrier discharge (GDBD) plasma-induced surface grafting of poly(vinylidene fluoride) (PVDF) membranes with mixed-charge copolymers of [2-(methacryloyloxy)ethyl] trimethylammonium (TMA) and sulfopropyl methacrylate (SA). The aim is to investigate the antifouling properties and the hemocompatibility of this system. We first characterize the physico-chemical properties of the membranes. With SA alone in the coating solution, efficient grafting cannot be achieved as monomer is blown away during grafting. Membranes grafted with a mixture of SA and TMA, or TMA alone do not meet this problem and grafting density ranged between 0.29 and 0.41 mg/cm2. Bovine-serum-albumin and lysozyme adsorption tests (70% reduction) and Escherichia coli attachment test (annihilation of adhesion) unveil that pseudo-zwitterionic PVDF membranes are very efficient to reduce biofouling in static condition. Different fouling resistance behaviors are observed in dynamic conditions. Permeability of virgin membranes progressively decreases over the cycles, arising from a gradual pore blockage and irreversible fouling. All potential adsorption sites of pseudo-zwitterionic membrane and membrane with positive charge-bias are fouled after the first cycle, and flux recovery is maximal in the following cycles. This behavior is ascribed to the lack of homogeneity of the surface grafting. Finally, pseudo-zwitterionic membranes are hemocompatible (resistance to blood cells, low hemolysis activity). Provided a better tuning of surface uniformity, the method and system presented in this work are a promising approach to the new generation of antifouling mixed-charge membranes for water treatment or blood contacting devices

Concept of Photoactive Invisible Inks toward Ultralow‐Cost Fabrication of Transistor Photomemories

Abstract Finding the outperforming photoactive charge trapping materials for a new‐trending transistor photomemory application is labor intensive, costly reagents and solvents, and not to mention, inefficient energy and time consumption. In this work, costless organic‐based inks are introduced as a novel photoactive charge storage material that is inspired by high fluorescent ink of cheap invisible pens when exposed to ultraviolet light. The pure powder inks of invisible pens with bright red and greenish‐yellow emission are selected. The estimated usage costs about $0.003 cm−2, confirming its ultralow‐budget material. The pentacene‐based organic field‐effect transistor memory scheme is employed to evaluate the memory behaviors. These invisible‐ink‐based charge storage layers endow a transistor memory device with photoinduced recovery. Interestingly, by conducting the photoassisted operation on the same device, its threshold voltage shifts toward more positive direction, resulting in broaden memory window and faster device operations. On top of that, invisible‐ink‐based transistor photomemory demonstrates the well‐defined and feasible multibit memory cell for the next‐generation storage media. As a result, the employment of commercial invisible inks as a cheapest photoactive charge trapping material can favor the advancement of transistor photomemory devices and related functional applications

Employing a green cross-linking method to fabricate polybenzimidazole (PBI) hollow fiber membranes for organic solvent nanofiltration (OSN)

Submitted version10.1016/j.seppur.2020.117702Separation and Purification Technology25511770