The Experts below are selected from a list of 46353 Experts worldwide ranked by ideXlab platform
Liquan Chen - One of the best experts on this subject based on the ideXlab platform.
-
Nafion organically modified silicate hybrids membrane for vanadium redox flow battery
Journal of Power Sources, 2009Co-Authors: Xiangguo Teng, Xinping Qiu, Liquan Chen, Yongtao ZhaoAbstract:In our previous work, Nafion/SiO(2) hybrid membrane was prepared via in situ sol-gel method and used for the vanadium redox flow battery (VRB) system. The VRB with modified Nafion membrane has shown great advantages over that of the VRB with Nafion membrane. In this work, a novel Nafion/organically modified silicate (ORMOSIL) hybrids membrane was prepared via in situ sol-gel reactions for mixtures of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS). The primary properties of Nafion/ORMOSIL hybrids membrane were measured and compared with Nafion and Nafion/SiO(2) hybrid membrane. The permeability of vanadium ions through the Nafion/ORMOSIL hybrids membrane was measured using an UV-vis spectrophotometer. The results indicate that the hybrids membrane has a dramatic reduction in crossover of vanadium ions compared with Nafion membrane. Fourier transform infrared spectra (FT-IR) analysis of the hybrids membrane reveals that the ORMOSIL phase is well formed within hybrids membrane. Cell tests identify that the VRB with Nafion/ORMOSIL hybrids membrane presents a higher coulombic efficiency (CE) and energy efficiency (EE) compared with that of the VRB with Nafion and Nafion/SiO(2) hybrid membrane. The highest EE of the VRB with Nafion/ORMOSIL hybrids membrane is 87.4% at 20mA cm(-2). while the EE of VRB with Nafion and the EE of VRB with Nafion/SiO(2) hybrid membrane are only 73.8% and 79.9% at the same current density. The CE and EE of VRB with Nafion/ORMOSIL hybrids membrane is nearly no decay after cycling more than 100 times (60mA cm(-2)), which proves the Nafion/ORMOSIL hybrids membrane possesses high chemical stability during long charge-discharge process under strong acid solutions. The self-discharge rate of the VRB with Nafion/ORMOSIL hybrids membrane is the slowest among the VRB with Nafion, Nafion/SiO(2) and Nafion/ORMOSIL membrane,which further proves the excellent vanadium ions blocking characteristic of the prepared hybrids membrane. (c) 2008 Elsevier B.V. All rights reserved.
-
Nafion sio2 hybrid membrane for vanadium redox flow battery
Journal of Power Sources, 2007Co-Authors: Xinping Qiu, Liquan ChenAbstract:Abstract Sol–gel derived Nafion/SiO2 hybrid membrane is prepared and employed as the separator for vanadium redox flow battery (VRB) to evaluate the vanadium ions permeability and cell performance. Nafion/SiO2 hybrid membrane shows nearly the same ion exchange capacity (IEC) and proton conductivity as pristine Nafion 117 membrane. ICP-AES analysis reveals that Nafion/SiO2 hybrid membrane exhibits dramatically lower vanadium ions permeability compared with Nafion membrane. The VRB with Nafion/SiO2 hybrid membrane presents a higher coulombic and energy efficiencies over the entire range of current densities (10–80 mA cm−2), especially at relative lower current densities (
Mu Pan - One of the best experts on this subject based on the ideXlab platform.
-
Nafion®—titania nanocomposite proton exchange membranes
Journal of Applied Polymer Science, 2010Co-Authors: Chuan Xiao, Wei Chen, Haining Zhang, Mu PanAbstract:Proton exchange membranes consisting of Nafion® and crystallized titania nanoparticles have been developed to improve water-retention and proton conductivity at elevated temperature and low relative humidity. The anatase-type titania nanoparticles were synthesized in situ in Nafion solution through sol–gel process and the size of the formed titiania nanoparticles is in the range of 3–6 nm. The formed nanoparticles are well-dispersed in Nafion solution at the titania concentration of 5 wt %. The glass transition temperature of the formed Nafion-titania composite membrane is about 20oC higher than that of plain Nafion membrane. At elevated temperature (above 100°C), the Nafion-titania nanocomposite membrane shows higher water uptake ability and improved proton conductivity compared to pure Nafion membrane. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
-
Nafion–zirconia nanocomposite membranes formed via in situ sol–gel process
International Journal of Hydrogen Energy, 2010Co-Authors: Jingjing Pan, Haining Zhang, Wei Chen, Mu PanAbstract:Abstract Crystallized zirconia nanoparticles with diameters of 6.3 ± 0.5 nm were in situ formed in Nafion solution through sol–gel process. Nafion molecules were self-assembled onto zirconia nanoparticles through electrostatic interactions and prevent the further growth of initial formed particles. The Nafion–zirconia nanocomposite membranes were formed using a recasting process. It was found that the addition of zirconia nanoparticles did not affect the crystallinity and structure of Nafion in the membrane significantly. The formed Nafion–zirconia nanocomposite membrane shows enhanced water retention ability at 100 °C compared to recast pure Nafion membrane, especially at medium and high relative humidity. This work demonstrates the potential of Nafion–zirconia nanocomposite membranes for PEMFC applications.
-
synthesis and characterization of a self assembled Nafion silica nanocomposite membrane for polymer electrolyte membrane fuel cells
Journal of Physical Chemistry C, 2008Co-Authors: Haolin Tang, Mu PanAbstract:A novel Nafion/SiO 2 nanocomposite membrane has been developed by combining the self-assembly route and Nafion/SiO 2 hybrids. Nafion-stabilized SiO 2 nanoparticles were synthesized by using the self-assembly route. The hydrolysis procedure has significant influence on the size and distribution of SiO 2 nanoparticles and the quality and performance of the composite membranes. Best results were obtained on the Nafion/SiO 2 composite membrane recast from Nafion−SiO 2 (5 wt %) nanoparticles with a H 2O:TEOS ratio of 4:1. The Nafion/SiO 2 composite membrane prepared by the self-assembled Nafion–SiO 2 nanoparticles shows remarkable durability as compared to the Nafion/SiO 2 composite membrane prepared by the conventional sol−gel method and pure Nafion 212 membrane, most likely due to the intimate interface between the self-assembled Nafion–SiO 2 nanoparticles and Nafion polymeric matrix. The tensile strength and proton conductivity of the self-assembled Nafion/SiO 2 nanocomposite membranes are 27.5 MPa and 0.09...
-
Zeta potential of Nafion molecules in isopropanol‐water mixture solvent
Journal of Applied Polymer Science, 2007Co-Authors: Haining Zhang, Jingjing Pan, Mu PanAbstract:Structure of Nafion in isopropanol/water mixture solvent has been investigated using zeta potential. It was found that zeta potential of Nafion strongly depends on the concentration. When the concentration of Nafion varied from 0.5 to 1 wt %, zeta potential increased significantly from about 0 to -12 mV, corresponding to the change of structure of Nafion molecules from true solution to dispersion of aggregates. While the concentration is above 5 wt %, micelle-like structure of Nafion aggregates was proposed. The dependence of zeta potential of Nafion on pH value at concentration of 5 wt % shows a nonmonotonic function and isoelectric point of Nafion-Na of 8.0 was observed.
-
Self-assembling multi-layer Pd nanoparticles onto Nafion membrane to reduce methanol crossover
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Haolin Tang, Mu Pan, San Ping Jiang, Zhaohui Wan, Run Zhang YuanAbstract:Abstract Methanol crossover through the proton exchange membranes (PEMs, e.g., Nafion™ membrane) is one of the major obstacles that currently prevent the widespread commercial applications of direct methanol fuel cell (DMFC). In this paper, multi-layer self-assembly Nafion™ membranes (MLSA Nafion™ membranes) were prepared by alternately assembling charged Pd particles and Nafion ionmers onto Nafion™ membranes. The Pd particles, size of about 1.8 nm in average, are charged by PDDA ionomers with zeta potential of 30 mV (pH value of 8.5). The Pd loading of the first-layer MLSA Nafion™ membranes was 0.63 μg cm −2 , and the surface coverage of the Pd nanoparticles on the Nafion™ membrane was estimated as 22%. After 5-double-layer Pd particles/Nafion ionomers assembling, the Pd loading reached to 2.86 μg cm −2 . The methanol crossover current of the original Nafion™ membranes and 1-double-layer, 2-double-layer, 3-double-layer, 4-double-layer, 5-double-layer MLSA Nafion™ membranes were 0.0495, 3.87E−3, 1.38E−3, 7.32E−4, 5.16E−4 and 4.25E−4 A cm −2 , respectively, corresponding conductivities of 0.112, 0.110, 0.105, 0.094, 0.087 and 0.081 S cm −2 . This satisfactory performance has given the MLSA Nafion™ membranes a promised prospect of using as proton exchange membrane in direct methanol fuel cells.
Xinping Qiu - One of the best experts on this subject based on the ideXlab platform.
-
a comparative study of Nafion series membranes for vanadium redox flow batteries
Journal of Membrane Science, 2016Co-Authors: Bo Jiang, Xinping QiuAbstract:Abstract In this study, a series of the commercial Nafion membranes (equivalent weight of 1100 g mol −1 ) with thickness of 50 μm (Nafion 112), 88 μm (Nafion 1135), 125 μm (Nafion 115), and 175 μm (Nafion 117) are selected to investigate the thickness impact of Nafion on the performance of vanadium redox flow battery (VRFB). VRFBs are evaluated at a broad current density range from 40 to 320 mA cm −2 . The self-discharge process, cell efficiencies, electrolyte utilization, and long-term cycling stability of VRFBs based on various Nafion membranes are compared comprehensively. Owing to the good balance between vanadium ions permeability and membrane resistance, Nafion 115 membrane presents the highest energy efficiency and electrolytes utilization at current density from 120 to 240 mA cm −2 . A simple and powerful online monitoring system is developed to monitor the electrolyte imbalance process during the cycle-life test of VRFB. The capacity fading mechanism of VRFBs with different Nafion membranes is also discussed.
-
Nafion organically modified silicate hybrids membrane for vanadium redox flow battery
Journal of Power Sources, 2009Co-Authors: Xiangguo Teng, Xinping Qiu, Liquan Chen, Yongtao ZhaoAbstract:In our previous work, Nafion/SiO(2) hybrid membrane was prepared via in situ sol-gel method and used for the vanadium redox flow battery (VRB) system. The VRB with modified Nafion membrane has shown great advantages over that of the VRB with Nafion membrane. In this work, a novel Nafion/organically modified silicate (ORMOSIL) hybrids membrane was prepared via in situ sol-gel reactions for mixtures of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS). The primary properties of Nafion/ORMOSIL hybrids membrane were measured and compared with Nafion and Nafion/SiO(2) hybrid membrane. The permeability of vanadium ions through the Nafion/ORMOSIL hybrids membrane was measured using an UV-vis spectrophotometer. The results indicate that the hybrids membrane has a dramatic reduction in crossover of vanadium ions compared with Nafion membrane. Fourier transform infrared spectra (FT-IR) analysis of the hybrids membrane reveals that the ORMOSIL phase is well formed within hybrids membrane. Cell tests identify that the VRB with Nafion/ORMOSIL hybrids membrane presents a higher coulombic efficiency (CE) and energy efficiency (EE) compared with that of the VRB with Nafion and Nafion/SiO(2) hybrid membrane. The highest EE of the VRB with Nafion/ORMOSIL hybrids membrane is 87.4% at 20mA cm(-2). while the EE of VRB with Nafion and the EE of VRB with Nafion/SiO(2) hybrid membrane are only 73.8% and 79.9% at the same current density. The CE and EE of VRB with Nafion/ORMOSIL hybrids membrane is nearly no decay after cycling more than 100 times (60mA cm(-2)), which proves the Nafion/ORMOSIL hybrids membrane possesses high chemical stability during long charge-discharge process under strong acid solutions. The self-discharge rate of the VRB with Nafion/ORMOSIL hybrids membrane is the slowest among the VRB with Nafion, Nafion/SiO(2) and Nafion/ORMOSIL membrane,which further proves the excellent vanadium ions blocking characteristic of the prepared hybrids membrane. (c) 2008 Elsevier B.V. All rights reserved.
-
Nafion sio2 hybrid membrane for vanadium redox flow battery
Journal of Power Sources, 2007Co-Authors: Xinping Qiu, Liquan ChenAbstract:Abstract Sol–gel derived Nafion/SiO2 hybrid membrane is prepared and employed as the separator for vanadium redox flow battery (VRB) to evaluate the vanadium ions permeability and cell performance. Nafion/SiO2 hybrid membrane shows nearly the same ion exchange capacity (IEC) and proton conductivity as pristine Nafion 117 membrane. ICP-AES analysis reveals that Nafion/SiO2 hybrid membrane exhibits dramatically lower vanadium ions permeability compared with Nafion membrane. The VRB with Nafion/SiO2 hybrid membrane presents a higher coulombic and energy efficiencies over the entire range of current densities (10–80 mA cm−2), especially at relative lower current densities (
Wei Xing - One of the best experts on this subject based on the ideXlab platform.
-
Self‐Healing Proton‐Exchange Membranes Composed of Nafion–Poly(vinyl alcohol) Complexes for Durable Direct Methanol Fuel Cells
Advanced Materials, 2018Co-Authors: Yixuan Li, Yang Li, Liang Liang, Wei XingAbstract:Proton-exchange membranes (PEMs) that can heal mechanical damage to restore original functions are important for the fabrication of durable and reliable direct methanol fuel cells (DMFCs). The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4-carboxybenzaldehyde (CBA) molecules is presented. Compared with pure Nafion, the CBA/Nafion-PVA membranes exhibit enhanced mechanical properties with an ultimate tensile strength of ≈20.3 MPa and strain of ≈380%. The CBA/Nafion-PVA membrane shows a proton conductivity of 0.11 S cm-1 at 80 °C, which is 1.2-fold higher than that of a Nafion membrane. The incorporated PVA gives the CBA/Nafion-PVA membranes excellent proton conductivity and methanol resistance. The resulting CBA/Nafion-PVA membranes are capable of healing mechanical damage of several tens of micrometers in size and restoring their original proton conductivity and methanol resistance under the working conditions of DMFCs. The healing property originates from the reversibility of hydrogen-bonding interactions between Nafion and CBA-modified PVA and the high chain mobility of Nafion and CBA-modified PVA.
-
Self-Healing Proton-Exchange Membranes Composed of Nafion-Poly(vinyl alcohol) Complexes for Durable Direct Methanol Fuel Cells.
Advanced Materials, 2018Co-Authors: Yixuan Li, Yang Li, Liang Liang, Wei XingAbstract:Proton-exchange membranes (PEMs) that can heal mechanical damage to restore original functions are important for the fabrication of durable and reliable direct methanol fuel cells (DMFCs). The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4-carboxybenzaldehyde (CBA) molecules is presented. Compared with pure Nafion, the CBA/Nafion-PVA membranes exhibit enhanced mechanical properties with an ultimate tensile strength of ≈20.3 MPa and strain of ≈380%. The CBA/Nafion-PVA membrane shows a proton conductivity of 0.11 S cm-1 at 80 °C, which is 1.2-fold higher than that of a Nafion membrane. The incorporated PVA gives the CBA/Nafion-PVA membranes excellent proton conductivity and methanol resistance. The resulting CBA/Nafion-PVA membranes are capable of healing mechanical damage of several tens of micrometers in size and restoring their original proton conductivity and methanol resistance under the working conditions of DMFCs. The healing property originates from the reversibility of hydrogen-bonding interactions between Nafion and CBA-modified PVA and the high chain mobility of Nafion and CBA-modified PVA.
-
surface modified Nafion membrane by casting proton conducting polyelectrolyte complexes for direct methanol fuel cells
Journal of Power Sources, 2007Co-Authors: Nanwen Li, Xiaochun Zhou, Jianhui Liao, Suobo Zhang, Wei XingAbstract:Abstract Surface-modified Nafion ® membrane was prepared by casting proton-conducting polyelectrolyte complexes on the surface of Nafion ® . The casting layer is homogeneous and its thickness is about 900 nm. The proton conductivity of modified Nafion ® is slightly lower than that of plain Nafion ® ; however, its methanol permeability is 41% lower than that of plain Nafion ® . The single cells with modified Nafion ® exhibit higher open circuit voltage (OCV = 0.73 V) and maximal power density ( P max = 58 mW cm −2 ) than the single cells with plain Nafion ® (OCV = 0.67 V, P max = 49 mW cm −2 ). It is a simple, efficient, cost-effective approach to modifying Nafion ® by casting proton-conducting materials on the surface of Nafion ® .
Yunfeng Zhai - One of the best experts on this subject based on the ideXlab platform.
-
modification of Nafion membrane using interfacial polymerization for vanadium redox flow battery applications
Journal of Membrane Science, 2008Co-Authors: Qingtao Luo, Huaming Zhang, Jian Chen, Peng Qian, Yunfeng ZhaiAbstract:Abstract In order to reduce the permeation of vanadium ions across the ion exchange membrane during the operation of vanadium redox flow battery (VRB) based on Nafion membrane, the interfacial polymerization was applied to form a cationic charged layer on the surface of Nafion 117 membrane. The area resistance and the permeability of vanadium ions were measured. The results indicate that comparing with the unmodified Nafion membrane, the modification of Nafion membrane results in a dramatic reduction in crossover of vanadium ions across the membrane and a little higher area resistance of the membrane. As a result, the columbic efficiency for the VRB single cell based on the modified Nafion membrane(VRB-modified Nafion), which is related to the concentration of the incubation solution of polyethylenimine (PEI), was increased significantly. The value is 96.2–97.3%, which is higher than that obtained with the VRB single cell based on unmodified Nafion membrane(VRB-Nafion) (around 93.8%). Due to the little higher area resistance caused by the modification, the voltage efficiency of VRB-modified Nafion is lower than that of VRB-Nafion. Furthermore, the water transfer across the modified membrane was also reduced. The ion exchange capacity (IEC) of the modified Nafion membrane was also evaluated. The formation of the thin cationic charged layer on the membrane surface was confirmed by IR spectra analysis.
