Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-c...Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-containing poly(fluorenyl ether ketone)s(QA-OMPFEKs) were prepared from the(i) condensation polymerization of a newly developed octa-benzylmethyl-containing bisphenol monomer via Ullmann coupling,(ii) bromination at the benzylmethyl sites using N-bromosuccinimide, and(iii)quaternization of the bromomethyl groups using trimethylamine. The QA-OMPFEK-20 with an ion exchange capacity(IEC) of 1.66 mmolg^-1 exhibited a higher SO42-conductivity(9.62mScm^-1) than that of the QA-TMPFEK-40(4.82mScm^-1) at room temperature, which had a slightly higher IEC of 1.73 mmolg-1but much lower QA density.The enhanced SO42-conductivity of QA-OMPFEK-20 was attributed to the ion-segregated structure arising from the densely anchored QA groups, which was validated by SAXS observation. Furthermore, the QA-OMPFEK-20 showed much lower VO2+permeability(1.24×10^-14m^2s^-1) than QA-TMPFEK-40(5.40×10^-13m^2s^-1) and Nafion N212(5.36×10^-12m^2s^-1), leading to improved Coulombic and energy efficiencies in Vanadium redox flow batteries(VRFBs). Therefore, the Ullmann coupling extension is a valuable approach for the development of high performance anion exchange membranes for VRFBs.展开更多
Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the...Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the ORR activity in 0.1 mol L-1 KOH and 0.1 tool L-1 K2CO3 at 25 ℃. Cyclic voltammetry （CV） was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode （RRDE） was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion （HO2-） as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.展开更多
A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)...A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)without ether bonds in the backbone and various quaternizing agents,including iodomethane,1-bromopentane,and(5-bromopentyl)-trimethylammonium bromide.The properties of the AEMs are investigated in terms of sulfuric acid doping content,swelling,vanadium permeability,ion selectivity,area-specific resistance,mechanical properties,VRFB performance,and cyclic testing.Particularly,a method of measuring the H^(+) permeability of the AEM is developed.It demonstrates that the poly(p-terphenyl-N-methylpiperidine)-quaternary ammonium(PTP-QA)membrane with a QA cation-tethered alkyl chain exhibits high H^(+) permeability,resulting in low area resistance.Combined with its low vanadium permeance,the PTP-QA membrane achieves nearly 370 times higher ion selectivity than Nafion 115.The VRFB based on PTP-QA-based AEM displays high Coulombic efficiencies above 99% at current densities of 80-160 mA cm^(-2).The higher energy efficiency of 89.8% is achieved at 100 mA cm^(-2)(vs.73.6% for Nafion 115).Meanwhile,the PTPQA-based AEM shows good cycling stability and capacity retention,proving great potential as the ion exchange membrane for VRFB applications.展开更多
基金supported by the National Natural Science Foundation of China (51503038)
文摘Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries.Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-containing poly(fluorenyl ether ketone)s(QA-OMPFEKs) were prepared from the(i) condensation polymerization of a newly developed octa-benzylmethyl-containing bisphenol monomer via Ullmann coupling,(ii) bromination at the benzylmethyl sites using N-bromosuccinimide, and(iii)quaternization of the bromomethyl groups using trimethylamine. The QA-OMPFEK-20 with an ion exchange capacity(IEC) of 1.66 mmolg^-1 exhibited a higher SO42-conductivity(9.62mScm^-1) than that of the QA-TMPFEK-40(4.82mScm^-1) at room temperature, which had a slightly higher IEC of 1.73 mmolg-1but much lower QA density.The enhanced SO42-conductivity of QA-OMPFEK-20 was attributed to the ion-segregated structure arising from the densely anchored QA groups, which was validated by SAXS observation. Furthermore, the QA-OMPFEK-20 showed much lower VO2+permeability(1.24×10^-14m^2s^-1) than QA-TMPFEK-40(5.40×10^-13m^2s^-1) and Nafion N212(5.36×10^-12m^2s^-1), leading to improved Coulombic and energy efficiencies in Vanadium redox flow batteries(VRFBs). Therefore, the Ullmann coupling extension is a valuable approach for the development of high performance anion exchange membranes for VRFBs.
文摘Plasma-synthesized cobalt oxide supported on carbon has been analyzed for its use for electrocatalytic oxygen reduction reaction （ORR） in alkaline anion exchange membrane fuel cells （AEMFC）. This work presents the ORR activity in 0.1 mol L-1 KOH and 0.1 tool L-1 K2CO3 at 25 ℃. Cyclic voltammetry （CV） was used to determine the potentials at which the ORR occurs and to evaluate the stability of catalyst. Moreover, a rotating ring-disk electrode （RRDE） was used to investigate the activity of the catalysts and the formation of the by-product hydroperoxide anion （HO2-） as well as to identify the preferred pathway of the ORR. Calculated kinetic parameters for the ORR for the cobalt catalysts are shown in this work together with a comparison to a commercial platinum catalyst. However, the cobalt oxide produced more by-products which could lead to damage of the membrane in a fuel cell through a radical attack of the polymer backbone.
基金supported by the National Natural Science Foundation of China(51603031)the Fundamental Research Funds for the Central Universities of China(N2005026)+1 种基金Liaoning Provincial Natural Science Foundation of China(20180550871 and 2020-MS-087)the Innovation Fund Denmark(DanFlow)。
文摘A new series of poly(arylene piperidinium)-based anion exchange membranes(AEMs)are proposed for vanadium redox flow batteries(VRFBs).The AEMs are fabricated via the Menshutkin reaction between poly(arylene piperidine)without ether bonds in the backbone and various quaternizing agents,including iodomethane,1-bromopentane,and(5-bromopentyl)-trimethylammonium bromide.The properties of the AEMs are investigated in terms of sulfuric acid doping content,swelling,vanadium permeability,ion selectivity,area-specific resistance,mechanical properties,VRFB performance,and cyclic testing.Particularly,a method of measuring the H^(+) permeability of the AEM is developed.It demonstrates that the poly(p-terphenyl-N-methylpiperidine)-quaternary ammonium(PTP-QA)membrane with a QA cation-tethered alkyl chain exhibits high H^(+) permeability,resulting in low area resistance.Combined with its low vanadium permeance,the PTP-QA membrane achieves nearly 370 times higher ion selectivity than Nafion 115.The VRFB based on PTP-QA-based AEM displays high Coulombic efficiencies above 99% at current densities of 80-160 mA cm^(-2).The higher energy efficiency of 89.8% is achieved at 100 mA cm^(-2)(vs.73.6% for Nafion 115).Meanwhile,the PTPQA-based AEM shows good cycling stability and capacity retention,proving great potential as the ion exchange membrane for VRFB applications.
