Naphthalene dianhydride based semifluorinated sulfonated copoly(ether imide)s: Synthesis, characterization and proton exchange properties

Sulfonated poly(arylene ether sulfone) functionalized polysilsesquioxane hybrid membranes with enhanced proton conductivity

Sulfopropylated polysilsesquioxane and –COOH containing fluorinated sulfonated poly(arylene ether sulfone) composite membranes (SPAES-SS-X) have been prepared via an in situ sol–gel reaction through the solution casting technique. The composite membranes showed excellent thermal and chemical stability, compared to the pristine SPAES membrane. The uniform dispersion of the sulfonated SiOPS nanoparticles on the polymer matrix was observed from the scanning electron microscope images. Atomic force microscopy and transmission electron microscopy images indicated significantly better phase-separated morphology and connectivity of the ionic domains of the composite membranes than the pristine SPAES membrane. The composite membranes showed considerable improvement in proton conductivity and oxidative stability than the pristine copolymer membrane under similar test conditions.

Biofouling effects on the performance of microbial fuel cells and recent advances in biotechnological and chemical strategies for mitigation

The occurrence of biofouling in MFC can cause severe problems such as hindering proton transfer and increasing the ohmic and charge transfer resistance of cathodes, which results in a rapid decline in performance of MFC. This is one of the main reasons why scaling-up of MFCs has not yet been successfully accomplished. The present review article is a wide-ranging attempt to provide insights to the biofouling mechanisms on surfaces of MFC, mainly on proton exchange membranes and cathodes, and their effects on performance of MFC based on theoretical and practical evidence. Various biofouling mitigation techniques for membranes are discussed, including preparation of antifouling composite membranes, modification of the physical and chemical properties of existing membranes, and coating with antifouling agents. For cathodes of MFC, use of Ag nanoparticles, Ag-based composite nanoparticles, and antifouling chemicals is outlined in considerable detail. Finally, prospective techniques for mitigation of biofouling are discussed, which have not been given much previous attention in the field of MFC research. This article will help to enhance understanding of the severity of biofouling issues in MFCs and provides up-to-date solutions. It will be beneficial for scientific communities for further strengthening MFC research and will also help in progressing this cutting-edge technology to scale-up, using the most efficient methods as described here.

Novel Sulfonated Co-poly(ether imide)s Containing Trifluoromethyl, Fluorenyl and Hydroxyl Groups for Enhanced Proton Exchange Membrane Properties: Application in Microbial Fuel Cell

A hydroxyl group containing new cardo diamine monomer was synthesized, namely 9,9-bis (hydroxy- (4'-amino(3-trifluoromethyl)biphenyl-4-oxy)-phenyl)-9H-fluorene (mixture of isomers, HAPHPF). HAPHPF, along with a sulfonated diamine monomer, 4,4'-diaminostilbene-2,2'-disulfonic acid (DSDSA), was used to prepare a series of new sulfonated copolyimides by polycondensation with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). The degree of sulfonation (DS < 1) was adjusted by the feed ratio of DSDSA/HAPHPF and the copolymers were named as DHN-XX, where XX denotes the mole percentage of DSDSA (XX = 50, 60, and 70). The copolymers showed high molecular weights. The copolymer structure and composition were confirmed by FTIR and NMR techniques. Copolymer membranes were prepared through solution cast route by using dimethyl sulfoxide as a solvent. The membranes showed high thermal, mechanical, hydrolytic and peroxide radical stability, and low water uptake and low swelling ratios. Well-separated hydrophilic and hydrophobic phase morphology was observed in TEM and AFM images of the copolymer membranes and was further supported by the SAXS studies. The proton conductivity of the DHN-70 was as high as 97 mS cm-1 at 80 °C and the value is significantly higher than that of the nonhydroxylated analogue. The membranes also showed superior microbial fuel cell (MFC) performance, similar like Nafion 117 under similar test conditions. The chemical oxygen demand removal values provide substantial evidence that the fabricated membranes can be utilized in bioelectrochemical systems.

A Low-Cost and High-Performance Sulfonated Polyimide Proton-Conductive Membrane for Vanadium Redox Flow/Static Batteries

A novel side-chain-type fluorinated sulfonated polyimide (s-FSPI) membrane is synthesized for vanadium redox batteries (VRBs) by high-temperature polycondensation and grafting reactions. The s-FSPI membrane has a vanadium ion permeability that is over an order of magnitude lower and has a proton selectivity that is 6.8 times higher compared to those of the Nafion 115 membrane. The s-FSPI membrane possesses superior chemical stability compared to most of the linear sulfonated aromatic polymer membranes reported for VRBs. Also, the vanadium redox flow/static batteries (VRFB/VRSB) assembled with the s-FSPI membranes exhibit stable battery performance over 100- and 300-time charge-discharge cycling tests, respectively, with significantly higher battery efficiencies and lower self-discharge rates than those with the Nafion 115 membranes. The excellent physicochemical properties and VRB performance of the s-FSPI membrane could be attributed to the specifically designed molecular structure with the hydrophobic trifluoromethyl groups and flexible sulfoalkyl pendants being introduced on the main chains of the membrane. Moreover, the cost of the s-FSPI membrane is only one-fourth that of the commercial Nafion 115 membrane. This work opens up new possibilities for fabricating high-performance proton-conductive membranes at low costs for VRBs.

Hexafluoroisopropylidene based sulfonated new copolytriazoles: investigation of proton exchange membrane properties

A series of novel sulfonated polytriazole copolymers (PTFOSH-XX) was successfully prepared by the click reaction of 4,4′-(perfluoropropane-2,2-diyl)bis((prop-2-ynyloxy)benzene (TF), 4,4′-diazido-2,2′-stilbene disulfonic acid disodium salt (SAZ) and 4,4′-diazidodiphenyl ether (OAZ). The copolymers were characterized by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed high mechanical, thermal and oxidative stability and low swelling. The phase separated morphology of the membranes was confirmed from transmission electron microscopy (TEM). The membranes showed proton conductivity as high as 110 and 122 mS cm−1 at 80 and 90°C, respectively depending on the polymer repeat unit structure.

New sulfonated copoly(triazole imide)s synthesized by a click chemistry reaction with improved oxidative stability

New sulfonated copoly(triazole imide)s synthesized by a click chemistry reaction with improved oxidative stability.

Highly sulfonated co-polyimides containing hydrophobic cross-linked networks as proton exchange membranes

The cross-linked highly sulfonated co-polyimides based on novel diamine monomer containing double hydrophobic cross-linkable tetrafluorostyrol side-groups showed improved enhanced dimensional stability and superior proton conductivity.

Highly sulfonated co-polyimides containing cross-linkable hydrophobic tetrafluorostyrol side-groups for proton exchange membranes

Highly sulfonated co-polyimides containing cross-linked hydrophobic side-groups showed improved comprehensive performance.

Cross-linked sulfonated poly(ether imide)/silica organic–inorganic hybrid materials: proton exchange membrane properties

A hybrid proton exchange membrane with enhanced oxidative and dimensional stability as well as reduced fuel crossover.

Highly proton conducting fluorinated sulfonated poly(arylene ether sulfone) copolymers with side chain grafting

A series of new copolymers HPPQSH-XX PS were synthesized from preformed sulfonated ionomers HPPQSH-XX in order to get high proton conductivity along with other excellent properties.