Jiangju Si

A Gemini Quaternary Ammonium Poly (ether ether ketone) Anion‐Exchange Membrane for Alkaline Fuel Cell: Design, Synthesis, and Properties

To reconcile the tradeoff between conductivity and dimensional stability in AEMs, a novel Gemini quaternary ammonium poly (ether ether ketone) (GQ-PEEK) membrane was designed and successfully synthesized by a green three-step procedure that included polycondensation, bromination, and quaternization. Gemini quaternary ammonium cation groups attached to the anti-swelling PEEK backbone improved the ionic conductivity of the membranes while undergoing only moderate swelling. The grafting degree (GD) of the GQ-PEEK significantly affected the properties of the membranes, including their ion-exchange capacity, water uptake, swelling, and ionic conductivity. Our GQ-PEEK membranes exhibited less swelling (≤ 40 % at 25-70 °C, GD 67 %) and greater ionic conductivity (44.8 mS cm(-1) at 75 °C, GD 67 %) compared with single quaternary ammonium poly (ether ether ketone). Enhanced fuel cell performance was achieved when the GQ-PEEK membranes were incorporated into H2 /O2 single cells.

In situ synthesis of Nanocomposite Membranes: Comprehensive Improvement Strategy for Direct Methanol Fuel Cells

In situ synthesis is a powerful approach to control nanoparticle formation and consequently confers extraordinary properties upon composite membranes relative to conventional doping methods. Herein, uniform nanoparticles of cesium hydrogen salts of phosphotungstic acid (CsPW) are controllably synthesized in situ in Nafion to form CsPW–Nafion nanocomposite membranes with both improved proton conductivity and methanol-crossover suppression. A 101.3% increase of maximum power density has been achieved relative to pristine Nafion in a direct methanol fuel cell (DMFC), indicating a potential pathway for large-scale fabrication of DMFC alternative membranes.

In situ construction of interconnected ion transfer channels in anion-exchange membranes for fuel cell application

To resolve the trade-off between conductivity and stability in anion-exchange membranes (AEMs), we proposed a strategy to modulate the membrane morphology from isolated ionic clusters to interconnected channels by precise adjustment of the amphiphilic architectures. From the perspective of AEM molecular designing, by synchronously increasing the amphiphilic segments, well-connected conductive nano-channels, comprising overlapped larger hydrophilic domains (35–40 nm), were constructed and validated by percolation theory. The whole synthesis process was green, avoiding the toxic chloromethyl methyl ether route. The unique molecular, spatial and micro-structures enabled the membranes to exhibit excellent performance. The connective hydrophilic channels significantly enhanced the conductivity, while the increasing hydrophobicity reduced the water uptake and swelling, improving the dimensional and chemical stability of the membranes. This strategy successfully solves the trade-off issue between conductivity and stability in AEMs.

Doping structure and degradation mechanism of polypyrrole–Nafion® composite membrane for vanadium redox flow batteries

A HPPY–N212 composite membrane was prepared by the in situ polymerization of pyrrole on Nafion® 212 substrate membrane, followed by sulfuric acid treatment. The proton-acid doping structure endowed the HPPY–N212 membrane with enhanced conductivity as well as reduced vanadium ion permeability. These unique properties enabled vanadium redox flow battery (VRFB) fabricated with HPPY–N212 membrane to exhibit better coulombic, voltage and energy efficiency than that with N212 membrane under current densities of 60–150 mA cm−2. However, a gradual decay of voltage and energy efficiency occurred during the charge–discharge cycles. The efficiency decay resulted from the irreversible damage to PPY doping structure caused by the over-oxidation during charge–discharge cycles. These investigations help better understand the structure–performance relationships and open up exciting opportunities for the development of new high-performance membranes for VRFBs.

A Bunch-Like Tertiary Amine Grafted Polysulfone Membrane for VRFBs with Simultaneously High Proton Conductivity and Low Vanadium Ion Permeability

Novel polysulfone membranes with bunch-like tertiary amine groups are synthesized with high ion selectivity and outstanding chemical stability for vanadium redox flow batteries (VRFBs). The bunch-like tertiary amine groups simultaneously act as an ionic conductor for proton hopping and vanadium ion transport obstacles. The performance of the membrane is tuned via controlling the grafting degree of the chloromethylated polysulfone. The results show that membranes show increasing proton over vanadium ion (σ/p) selectivity with increasing functional tertiary groups. VRFBs assembled with the prepared membranes demonstrate an impressive Coulombic efficiency of 98.9% and energy efficiency of 90.9% at a current density of 50 mA cm-2 . Furthermore, the prepared membrane reported in this work shows excellent stability in 1 m VO2+ solution at 35 °C over 240 h. Overall, the synthesized polymers provide a new insight into the design of high-performance membranes toward VRFB applications.

A low-toxic artificial fluorescent glycoprotein can serve as an efficient cytoplasmic labeling in living cell.

To maintain the virtue of good optical property and discard the dross of conventional fluorescent staining dyes, we provide a strategy for designing new fluorescent scaffolds. In this study, a novel fluorescent labeling glycoprotein (chitosan-poly-L-cysteine, CPC) was synthesized through graft copolymerization. CPC gives emission peak at 465-470 nm when excited at 386 nm. The submicro-scale CPC microspheres could be localized and persisted specifically in the cytoplasm of living cells, with strong blue fluorescence. Moreover, CPC was highly resistant to photo bleaching, the fluorescence was remained stable for up to 72 h as the cells grew and developed. The glycoprotein CPC was bio-compatible and in zero grade cytotoxicity as quantified by MTT assay. The fluorescent labeling process with our newly designed glycoprotein CPC is exceptionally efficient.