In this work,a series of high strength,thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole(PBI)as the matrix and perfluorosulfonic acid(PFSA)as the fortif...In this work,a series of high strength,thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole(PBI)as the matrix and perfluorosulfonic acid(PFSA)as the fortifier for proton exchange.Solution processible PBI was successfully synthesized by introducing 4,4’-dicarboxydiphenyl ether into the molecular chains of PBI.PFSA/PBI composite membranes were obtained by solution blending and film casting.PBI and PFSA/PBI composite membranes exhibited greatly enhanced tensile strength and Young’s modulus compared to PFSA.PFSA/PBI composite membranes are stable below 300℃ which are suitable for practical application in proton exchange membrane fuel cells.The PFSA/PBI composite membranes show good dimensional stability with low water uptake and swelling rate.The PFSA/PBI composite membranes also exhibit excellent antioxidation stability with less than 5%initial mass loss over 120 h in Fenton reagent.The proton conductivity of PBI is greatly enhanced by blending with PFSA and the proton conductivities of the composite membranes are increased with the raise of PFSA content and temperature.This work offers valuable insights into the exploration of PBI based high-performance proton exchange membranes.展开更多
Molecular dynamics simulations were conducted to investigate the effects of side-chain structure and spacing on the self-assembly behaviors of perfluorosulfonic acid(PFSA)ionomers in both bulk proton exchange membrane...Molecular dynamics simulations were conducted to investigate the effects of side-chain structure and spacing on the self-assembly behaviors of perfluorosulfonic acid(PFSA)ionomers in both bulk proton exchange membrane(PEM)and nano-thin films within the catalyst layer(CL)for PEM fuel cells.Differences and interconnections between the two systems were highlighted;and the local oxygen transport properties at Pt/ionomer interfaces are analyzed.Results reveal that the side-chain length predominantly influence the size of primary sulfonate aggregates and the formation of the secondary aggregates,respectively,thereby playing distinct roles in the connectivity of proton-conducting hydrophilic domains.Specifically,in bulk system,the connectivity was primarily determined by the sizes of the secondary aggregate,making the side-chain spacing a critical factor;whereas in CL,combined effects of nanoscale confinement and ionomer-catalyst interactions restrict the formation of secondary sulfonate aggregates,rendering the size of primary aggregates and thus the side-chain length more important.Besides,although longer side chains with flexible ether groups enhance microphase separation,they also intensify high backbone aggregation,leading to inhomogeneous ionomer distribution and impeded proton transport in CL.A negative correlation is observed between the oxygen flux and the backbone aggregation on Pt.As a result,among the PFSA ionomers studied,the one with medium-length and closely spaced side chains(3M877)exhibited the most favorable self-assembly characteristics for CL applications,balancing both the proton conduction and oxygen permeability.These findings provide crucial molecular-level insights into optimization of ionomer side chain structures toward PEM and CL.展开更多
Preparation and characterization of perfluorosulfonic resin/titania organic-inorganic hybrid films were presented. The transparent hybrid films were prepared by hydrothermal treatment at low temperature of a mixed sol...Preparation and characterization of perfluorosulfonic resin/titania organic-inorganic hybrid films were presented. The transparent hybrid films were prepared by hydrothermal treatment at low temperature of a mixed solution of tetrabutyl titanate and perfluorosulfonic resin with the help of acetylacetone. The characterization was carried out by SEM,XRD,FT-IR,UV-Vis and TGA. The results showed that the perfluorosulfonic resin/titania hybrid transparent films were composed of titania particles dispersed in the perfluorosulfonic resin matrix very well and the titania was of anatase phase. Its diameter de-creased with increasing weight ratio of titania to perfluorosulfonic resin.展开更多
This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxid...This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid membrane is formed. Measurements of mechanical properties reveal that elastic modulus and hardness of the hybrid membrane are about 2 times compared to a commercial PFSA membrane. Scanning electron microscopy (SEM) results show that the hybrid membrane has a high porosity. Inside the membrane pores, there exists a great quantity of micro scale channels in the range of 100―300 nm. After fabrication of IPMC actuator, an electric current sensor, a force sensor, and a high speed camera are assembled and used to evaluate IPMC performance. It is shown that, compared to an IPMC actuator made from a commercial membrane, the electromechanical performance of the new actuator increases 6―8 times; when it is actuated in air, its stable non-water working time is prolonged for 6―7 times.展开更多
Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt s...Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt substituted perfluorosulfonic acid/polytetrafluoroethylene copolymer and dicyandiamide as the pyrolysis precursor to synthesize nitrogen-doped carbon nanotube(N–CNT) encapsulating cobalt nanoparticles hybrid material. The carbon layers and specific surface area of N–CNT have a critical role to the ORR performance due to the exposed active sites, determined by the mass ratio of the two precursors. The optimum hybrid material exhibits high ORR activity and stability, as well as excellent performance and durability in zinc–air battery.展开更多
The intrinsic viscosity and viscometric interaction parameters of perfluorosulfonic acid （PFSA） and poly（vinyl alcohol） （PVA） were measured by dilute solution viscometry. The miscibility between PFSA and PVA was...The intrinsic viscosity and viscometric interaction parameters of perfluorosulfonic acid （PFSA） and poly（vinyl alcohol） （PVA） were measured by dilute solution viscometry. The miscibility between PFSA and PVA was estimated by the criteria of AB and μ. The results indicated that PFSA and PVA were completely miscible for any weight fraction in aqueous solution.展开更多
High performance polyvinylidene fluoride （PVDF） flat sheet ultrafiltration （UF） membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid （PFSA） as a pore for...High performance polyvinylidene fluoride （PVDF） flat sheet ultrafiltration （UF） membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid （PFSA） as a pore former and as a hydrophilic component of the membranes and polyethylene glycol （Mw = 400） （PEG400） as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin （BSA） protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane （5 wt-% PEG400 ＋ 5 wt-% PFSA） had a pure water flux of 141.7L/m2.h, a BSA rejection of 90.1% and a relative pure water flux reduction （RFR） of 15.28%. These properties were greatly superior to those of the native PVDF membrane （pure water flux of 5.6 L/m2. h, BSA rejection of 96.3% and RFR of 42.86%）.展开更多
The performance of proton exchange membrane fuel cells (PEMFC) is strongly determined by the structure and composition of the electrode layer.The interactions between the ionomer,carbon black particles,and solvent aff...The performance of proton exchange membrane fuel cells (PEMFC) is strongly determined by the structure and composition of the electrode layer.The interactions between the ionomer,carbon black particles,and solvent affect the suspension properties and thus the layer morphology.We analyze the effect of the ionomer-to-carbon (I/C) weight ratio for two different types of carbon black on the suspension and layer characteristics.Highly branched carbon blacks with a high surface area tend to form less cracked layers.As less branched carbons can pack together more closely,a smaller pore size results in a larger capillary pressure during drying and thus more cracks.The added ionomer adsorbs on the carbon particles and improves the colloidal stability of the carbon black particles.The carbon black aggregates are thus smaller,resulting in closer packing and thinner layers.Moreover,the addition of the ionomer increases the critical coating thickness (CCT) of the layers because drying stresses are dissipated by the deformation of the ionomer,preventing crack formation.An optimum I/C weight ratio is identified for optimal layer formation and minimized crack formation.展开更多
Mechanical failure modes leading to cracks or breeches in proton exchange membrane fuel cells are driven by mechanical forces associated with swelling from water uptake and shrinkage from dehumidifi- cation. To determ...Mechanical failure modes leading to cracks or breeches in proton exchange membrane fuel cells are driven by mechanical forces associated with swelling from water uptake and shrinkage from dehumidifi- cation. To determine the magnitude of compressive mechanical stress imposed by water swelling in a proton exchange fuel-cell membrane, the osmotic pressure of water in a perfluorosulfonic acid ionomer （Nation N 117） membrane was measured using a hydrostatic piston-cylinder device with an in-situ hydrophilic frit. Experiments indicate that hydrostatic stresses greater than 103.5 MPa are created in a membrane when swollen with water at 23℃ suggesting that pressure from water swelling can distort Nafion N 117-based structures as the osmotic pressure is of the same order of magnitude as the flow stress of Nation N 117.展开更多
Intrinsic emission from unorthodox luminogens without traditional conjugated building blocks is drawing increasing attention.However,the emission mechanism is still controversial.Herein,we demonstrate the intriguing e...Intrinsic emission from unorthodox luminogens without traditional conjugated building blocks is drawing increasing attention.However,the emission mechanism is still controversial.Herein,we demonstrate the intriguing emission from perfluorosulfonate ionomers(PFSIs),which can be explained by the clustering triggered emission(CTE)mechanism.Despite being free of any conventional chromophores,PFSIs exhibit bright emission and multi-color phosphorescence(77 K)in concentrated solutions,powders and membranes with obvious aggregation-induced emission(AIE)characteristics.Clustered sulfonic acids are responsible for the light emission,and their connection and evolution are deeply explored via X-ray diffraction(XRD)and small angel X-ray scattering(SAXS),in which the electron overlap determined by the clustered status results in the extended conjugation and simultaneously rigidified conformations.These results demonstrate that it is feasible to use fluorescence analysis to explore the ionic cluster structure and evolution of PFSI,and it can be applied in the pure organic luminescent field as well.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.22005147 and 21774053)。
文摘In this work,a series of high strength,thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole(PBI)as the matrix and perfluorosulfonic acid(PFSA)as the fortifier for proton exchange.Solution processible PBI was successfully synthesized by introducing 4,4’-dicarboxydiphenyl ether into the molecular chains of PBI.PFSA/PBI composite membranes were obtained by solution blending and film casting.PBI and PFSA/PBI composite membranes exhibited greatly enhanced tensile strength and Young’s modulus compared to PFSA.PFSA/PBI composite membranes are stable below 300℃ which are suitable for practical application in proton exchange membrane fuel cells.The PFSA/PBI composite membranes show good dimensional stability with low water uptake and swelling rate.The PFSA/PBI composite membranes also exhibit excellent antioxidation stability with less than 5%initial mass loss over 120 h in Fenton reagent.The proton conductivity of PBI is greatly enhanced by blending with PFSA and the proton conductivities of the composite membranes are increased with the raise of PFSA content and temperature.This work offers valuable insights into the exploration of PBI based high-performance proton exchange membranes.
基金supported by the National Natural Science Foundation of China(No.22332004)the China Postdoctoral Science Foundation under Grant(No.GZC20231962)+1 种基金Generous grants of computer time at the Supercomputing Center of Wuhan University are gratefully acknowledgedThe authors acknowledge the support of the Supercomputing Center of Wuhan University.
文摘Molecular dynamics simulations were conducted to investigate the effects of side-chain structure and spacing on the self-assembly behaviors of perfluorosulfonic acid(PFSA)ionomers in both bulk proton exchange membrane(PEM)and nano-thin films within the catalyst layer(CL)for PEM fuel cells.Differences and interconnections between the two systems were highlighted;and the local oxygen transport properties at Pt/ionomer interfaces are analyzed.Results reveal that the side-chain length predominantly influence the size of primary sulfonate aggregates and the formation of the secondary aggregates,respectively,thereby playing distinct roles in the connectivity of proton-conducting hydrophilic domains.Specifically,in bulk system,the connectivity was primarily determined by the sizes of the secondary aggregate,making the side-chain spacing a critical factor;whereas in CL,combined effects of nanoscale confinement and ionomer-catalyst interactions restrict the formation of secondary sulfonate aggregates,rendering the size of primary aggregates and thus the side-chain length more important.Besides,although longer side chains with flexible ether groups enhance microphase separation,they also intensify high backbone aggregation,leading to inhomogeneous ionomer distribution and impeded proton transport in CL.A negative correlation is observed between the oxygen flux and the backbone aggregation on Pt.As a result,among the PFSA ionomers studied,the one with medium-length and closely spaced side chains(3M877)exhibited the most favorable self-assembly characteristics for CL applications,balancing both the proton conduction and oxygen permeability.These findings provide crucial molecular-level insights into optimization of ionomer side chain structures toward PEM and CL.
基金Supported by the Hi-Tech Research and Development Program of China (863 Pro-gram)(Grant No. 2004AA329010)
文摘Preparation and characterization of perfluorosulfonic resin/titania organic-inorganic hybrid films were presented. The transparent hybrid films were prepared by hydrothermal treatment at low temperature of a mixed solution of tetrabutyl titanate and perfluorosulfonic resin with the help of acetylacetone. The characterization was carried out by SEM,XRD,FT-IR,UV-Vis and TGA. The results showed that the perfluorosulfonic resin/titania hybrid transparent films were composed of titania particles dispersed in the perfluorosulfonic resin matrix very well and the titania was of anatase phase. Its diameter de-creased with increasing weight ratio of titania to perfluorosulfonic resin.
基金Supported by the National Natural Key Science Foundation of China (Grant No. 60535020)National Natural Science Foundation of China (Grant Nos. 50705043 and 50805076)Natural Science Foundation of Jiangsu Province (Grant No. 2007202)
文摘This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid membrane is formed. Measurements of mechanical properties reveal that elastic modulus and hardness of the hybrid membrane are about 2 times compared to a commercial PFSA membrane. Scanning electron microscopy (SEM) results show that the hybrid membrane has a high porosity. Inside the membrane pores, there exists a great quantity of micro scale channels in the range of 100―300 nm. After fabrication of IPMC actuator, an electric current sensor, a force sensor, and a high speed camera are assembled and used to evaluate IPMC performance. It is shown that, compared to an IPMC actuator made from a commercial membrane, the electromechanical performance of the new actuator increases 6―8 times; when it is actuated in air, its stable non-water working time is prolonged for 6―7 times.
基金financial support from the Ministry of Science and Technology of China(Grants 2016YFB0600901 and 2013CB933100)the National Natural Science Foundation of China(Grants 21573222 and 91545202)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB17020200)financial support from CAS Youth Innovation Promotion(Grant No.2015145)
文摘Nitrogen-doped carbon materials encapsulating 3 d transition metals are promising alternatives to replace noble metal Pt catalysts for efficiently catalyzing the oxygen reduction reaction(ORR). Herein, we use cobalt substituted perfluorosulfonic acid/polytetrafluoroethylene copolymer and dicyandiamide as the pyrolysis precursor to synthesize nitrogen-doped carbon nanotube(N–CNT) encapsulating cobalt nanoparticles hybrid material. The carbon layers and specific surface area of N–CNT have a critical role to the ORR performance due to the exposed active sites, determined by the mass ratio of the two precursors. The optimum hybrid material exhibits high ORR activity and stability, as well as excellent performance and durability in zinc–air battery.
基金supported by the Innovation Program of Shanghai Municipal Education Commission (Grant No.09YZ163)
文摘The intrinsic viscosity and viscometric interaction parameters of perfluorosulfonic acid （PFSA） and poly（vinyl alcohol） （PVA） were measured by dilute solution viscometry. The miscibility between PFSA and PVA was estimated by the criteria of AB and μ. The results indicated that PFSA and PVA were completely miscible for any weight fraction in aqueous solution.
基金Acknowledgements The work was supported by the National Natural Science Foundation of China （Grant No. 20904031） and the Shanghai Leading Academic Discipline Project （No, B202）. Thanks for Instrumental Analysis Center of Shanghai Jiao Tong University.
文摘High performance polyvinylidene fluoride （PVDF） flat sheet ultrafiltration （UF） membranes have been prepared by an immersion precipitation phase inversion method using perfluorosulfonic acid （PFSA） as a pore former and as a hydrophilic component of the membranes and polyethylene glycol （Mw = 400） （PEG400） as a pore forming agent. The effects of the presence of PEG and the concentration of the PFSA on the phase separation of the casting solutions and on the morphologies and performance of UF membranes including their porosity, water flux, rejection of bovine serum albumin （BSA） protein, and anti-fouling property were investigated. Phase diagrams, viscosities and the phase separations upon exposure to water vapor showed that both PEG400 and PFSA promoted demixing of the casting solution. Scanning electron microscopy measurements showed that the PVDF-PFSA blend membranes had more macropores and finger-like structures than the native PVDF membranes. The PVDF-PFSA membrane （5 wt-% PEG400 ＋ 5 wt-% PFSA） had a pure water flux of 141.7L/m2.h, a BSA rejection of 90.1% and a relative pure water flux reduction （RFR） of 15.28%. These properties were greatly superior to those of the native PVDF membrane （pure water flux of 5.6 L/m2. h, BSA rejection of 96.3% and RFR of 42.86%）.
文摘The performance of proton exchange membrane fuel cells (PEMFC) is strongly determined by the structure and composition of the electrode layer.The interactions between the ionomer,carbon black particles,and solvent affect the suspension properties and thus the layer morphology.We analyze the effect of the ionomer-to-carbon (I/C) weight ratio for two different types of carbon black on the suspension and layer characteristics.Highly branched carbon blacks with a high surface area tend to form less cracked layers.As less branched carbons can pack together more closely,a smaller pore size results in a larger capillary pressure during drying and thus more cracks.The added ionomer adsorbs on the carbon particles and improves the colloidal stability of the carbon black particles.The carbon black aggregates are thus smaller,resulting in closer packing and thinner layers.Moreover,the addition of the ionomer increases the critical coating thickness (CCT) of the layers because drying stresses are dissipated by the deformation of the ionomer,preventing crack formation.An optimum I/C weight ratio is identified for optimal layer formation and minimized crack formation.
文摘Mechanical failure modes leading to cracks or breeches in proton exchange membrane fuel cells are driven by mechanical forces associated with swelling from water uptake and shrinkage from dehumidifi- cation. To determine the magnitude of compressive mechanical stress imposed by water swelling in a proton exchange fuel-cell membrane, the osmotic pressure of water in a perfluorosulfonic acid ionomer （Nation N 117） membrane was measured using a hydrostatic piston-cylinder device with an in-situ hydrophilic frit. Experiments indicate that hydrostatic stresses greater than 103.5 MPa are created in a membrane when swollen with water at 23℃ suggesting that pressure from water swelling can distort Nafion N 117-based structures as the osmotic pressure is of the same order of magnitude as the flow stress of Nation N 117.
基金supported by the Petrochina Petrochemical Research Institute(LH-17-02-07-05)Open Foundation from State Key Laboratory of Fluorinated Functional Membrane Material。
文摘Intrinsic emission from unorthodox luminogens without traditional conjugated building blocks is drawing increasing attention.However,the emission mechanism is still controversial.Herein,we demonstrate the intriguing emission from perfluorosulfonate ionomers(PFSIs),which can be explained by the clustering triggered emission(CTE)mechanism.Despite being free of any conventional chromophores,PFSIs exhibit bright emission and multi-color phosphorescence(77 K)in concentrated solutions,powders and membranes with obvious aggregation-induced emission(AIE)characteristics.Clustered sulfonic acids are responsible for the light emission,and their connection and evolution are deeply explored via X-ray diffraction(XRD)and small angel X-ray scattering(SAXS),in which the electron overlap determined by the clustered status results in the extended conjugation and simultaneously rigidified conformations.These results demonstrate that it is feasible to use fluorescence analysis to explore the ionic cluster structure and evolution of PFSI,and it can be applied in the pure organic luminescent field as well.
