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
Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration(UF) membrane as substrate with recovered PFSA.The composite membranes we...Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration(UF) membrane as substrate with recovered PFSA.The composite membranes were applied to the pervaporation separation of 95% ethanol(EtOH)/H2O mixture.SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm,much thinner than those of other PFSA composite membranes revealed in the literatures.Effects of annealing temperature,coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated.The total flux decreases and separation factor increases with the increase of annealing temperature.The highest permeation flux of 3230 g m-2 h-1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C.The lowest permeation flux of 396 g m-2 h-1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C.The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA.The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H+>Li+>Ca2+>Mg2+>Na+>K+>Ba2+>Fe3+>Al3+,and the separation factor sequence is H+<Li+<Al3+<Na+<Mg2+<Ca2+<K+ <Ba2+<Fe3+.The apparent activation energy △Eapp values of the composite membranes with different counter-ions were calculated by Arrhenius law.The sequence of △Eapp values for the membranes with monovalent counter-ions is Li+>Na+>K+.There are very little variations of △Eapp values between the composite membranes with three divalent counterions(Mg2+,Ca2+ and Ba2+),and the △Eapp values of the composite membranes with two trivalent counterions(Fe3+ and Al3+) are relatively high.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
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supported by the Leading Academic Discipline Project of SHNU (No.DZL807)Innovation Program of Shanghai Municipal Education Commission (No.09YZ163)Shanghai Municipal Natural Science Foundation (No.09ZR1423300)
文摘Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration(UF) membrane as substrate with recovered PFSA.The composite membranes were applied to the pervaporation separation of 95% ethanol(EtOH)/H2O mixture.SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm,much thinner than those of other PFSA composite membranes revealed in the literatures.Effects of annealing temperature,coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated.The total flux decreases and separation factor increases with the increase of annealing temperature.The highest permeation flux of 3230 g m-2 h-1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C.The lowest permeation flux of 396 g m-2 h-1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C.The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA.The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H+>Li+>Ca2+>Mg2+>Na+>K+>Ba2+>Fe3+>Al3+,and the separation factor sequence is H+<Li+<Al3+<Na+<Mg2+<Ca2+<K+ <Ba2+<Fe3+.The apparent activation energy △Eapp values of the composite membranes with different counter-ions were calculated by Arrhenius law.The sequence of △Eapp values for the membranes with monovalent counter-ions is Li+>Na+>K+.There are very little variations of △Eapp values between the composite membranes with three divalent counterions(Mg2+,Ca2+ and Ba2+),and the △Eapp values of the composite membranes with two trivalent counterions(Fe3+ and Al3+) are relatively high.
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.
