We synthesized nanometer-thick ZSM-5 nanosheets to form laminated thin membranes for enhanced desalination of concentrated brines.

Non-aqueous redox flow batteries (RFBs) are promising energy storage devices owing to the broad electrochemical window of organic solvents. Nonetheless, the wide application of these batteries has been limited by the low stability and limited solubility of organic materials, as well as the insufficient ion conductivity of the cell separators in non-aqueous electrolytes. In this study, two viologen analogues with poly­(ethylene glycol) (PEG) tails are designed as anolytes for non-aqueous RFBs. The PEGylation of viologen not only enhances the solubility in acetonitrile but also increases the overall molecular size for alleviated crossover. In addition, a composite nanoporous aramid nanofiber separator, which allows the permeation of supporting ions while inhibiting the crossover of the designer viologens, is developed using a scalable doctor-blading method. Paired with ferrocene, the full organic material-based RFB presents excellent cyclability (500 cycles) with a retention capacity per cycle of 99.93% and an average Coulombic efficiency of 99.3% at a current density of 2.0 mA/cm2. The high performance of the PEGylated viologen validates the potential of the PEGylation strategy for enhanced organic material-based non-aqueous RFBs.

The ionic ZSM-5 zeolite membranes were investigated for proton-selective ion separation in electrolyte solutions relevant to redox flow batteries. The zeolite membrane achieved exceptional selectivity for proton over V4+ (VO2+), Cr2+, and Fe2+ via size-exclusion at the zeolitic channel openings, and remarkably low area specific resistance resulted from its hydrophilic surface, copious extraframework protons, and micron-scale thickness. The ZSM-5 membrane, as a new type of ion separator, demonstrated substantially reduced self-discharge rates and enhanced efficiencies for the all-vanadium and iron–chromium flow batteries as compared to the benchmark Nafion membrane. Findings of this research show that ionic microporous zeolite membranes can potentially overcome the challenge of trade-off between ion selectivity and conductivity associated with conventional polymeric ion separators.

DDR-type zeolite membrane was synthesized on porous α-alumina substrate by hydrothermal treatment of a ball-milled Sigmal-1 crystal seed layer in an aluminum-free precursor solution containing 1-Adamantylamine as the structure directing agent. The as-synthesized DDR zeolite membranes were defect-free but the supported zeolite layers were susceptible to crack development during the subsequent high-temperature SDA removal process. The cracks were effectively eliminated by the liquid phase chemical deposition method using tetramethoxysilane as the precursor for silica deposits. The modified membrane was extensively studied for H 2 , He, O 2 , N 2 , CO 2 , CH 4 , and i-C 4 H 10 pure gas permeation and CO 2 /CH 4 mixture separation. At 297 K and 2-bar feed gas pressure, the membrane achieved a CO 2 /CH 4 separation factor of ~92 for a feed containing 90% CO 2 , which decreased to 62 for a feed containing 10% CO 2 with the CO 2 permeance virtually unchanged at ~1.8 × 10-7 mol/m 2 •s•Pa regardless of the feed composition. It also exhibited an O 2 /N 2 permselectivity of 1.8 at 297 K. The gas permeation behaviors of the current aluminum-containing DDR type zeolite membrane are generally in good agreement with the findings in both experimental and theoretical studies on the pure-silica DDR membranes in recent literature.

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