PDF Publication Title:
Text from PDF Page: 004
4 J. Sheng et al. / Materials Today Nano 7 (2019) 100044 Fig. 2. (a) Schematic principle of nanofiltration membranes in the VRFB. Reproduced from Zhang et al. [36] with permission from the Royal Society of Chemistry. (b) VRFB single-cell performance of the tetraethyl orthosilicateetreated membrane under different current densities. Reproduced from Zhang et al. [37] with permission from the Royal Society of Chemistry. Cross-sectional field emission scanning electron microscope (FESEM) image (c) and pore size distribution obtained using mercury intrusion porosimetry (d) of the PVC/silica separator. Reproduced from Wei et al. [40] with permission from The Electrochemical Society. CE, coulombic efficiency; VE, voltage efficiency; EE, energy efficiency; PVC, polyvinyl chloride. Furthermore, Yuan et al. [59] proposed a highly ion-selective membrane created by coating an 8-mm thick layer of zeolites, which are crystalline and microporous aluminosilicates with peri- odic cage-like arrangements on a porous PES substrate (Fig. 4b). Zeolites possess high proton conductivity owing to the existence of large numbers of exchangeable cation sites that can be exchanged for protons at the interlinked SiO4 and AlO4 tetrahedra (Fig. 4c). The high selectivity was obtained by incorporating ZSM-35 as the zeolite scaffold that contains pores of 0.42 nm 0.54 nm, which is smaller than the stoke radii of protons (0.24 nm for H5Oþ2 ) but larger than the hydrated vanadium ions (0.6 nm). The composite membrane demonstrated high chemical stability and a low area specific resistance of 0.98 U cm2, leading to a current efficiency of 98.82% and an EE of 91.41% at a current density of 80 mA cm2. On the contrary, the battery using the Nafion 115 membrane can only achieve a current efficiency of 93.19% and an EE of 82.30%, simply owing to the higher vanadium ion permeability of Nafion 115econtaining hydrophilic water channels of 2.5-nm diameter. The zeolite-coated membrane has also displayed higher efficiencies than Nafion 115 and a stable cycling performance for 100 cycles. Meanwhile, Lu et al. [60] reported an uncharged highly selective porous membrane by tuning the pore size and pore distribution of the PES membrane using solvent treatment, as illustrated in Fig. 4d. PES membranes with large and well-interconnected pores were created by the phase inversion method and further adjusted by introducing PVP into the casting solution. They further treated the porous membranes by immersing into isopropyl alcohol (IPA), fol- lowed by a controlled solvent evaporation process. During the solvent treatment, a swelling force acts on the membranes causing a reorganization of the polymer chains owing to the enhancement in their mobility, whereas during the controlled evaporation pro- cess, a cohesive force initiates the pore shrinkage. These two forces are equal at equilibrium, but the balance disrupts owing to the solvent treatment causing relatively higher shrinkage in the pores than the starting states of the membranes. This unique concept of achieving higher ion selectivity and the tuned morphology of the PES matrix is chemically more stable than Nafion 115, and the ob- tained CE and EE is higher than Nafion 115. However, the mem- brane only exhibited stable cycling for 120 cycles, and further improvement is needed to increase the lifetime of the membrane. Similar perception of increasing the viscosity to limit the mass exchange rate and allow crystallization much earlier to gain higher crystallinity in the polyvinylidene fluoride (PVDF) ultrafiltration membrane with hydrophobic pores (Fig. 5a) was reported by Wei et al. [61]. PVDF is a semicrystalline polymer with at least four distinctive phases a, b, g, and d, and the crystallization together with the liquid-liquid demixing plays a crucial role in the obtained morphology of the phase-separated membranes. Li et al. [62] re- ported a membrane configuration by mixing PVDF and sodium allylsulfonate, where the pore size was controlled by the temper- ature and the time of polymer crystallization, as demonstrated in Fig. 5b. In this case, the morphology of the membranes wasPDF Image | membrane for aqueous redox flow batteries
PDF Search Title:
membrane for aqueous redox flow batteriesOriginal File Name Searched:
ion selective memberane.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |