Proton conducting composite membranes from polysulfone and heteropolyacid for fuel cell applications

The viability of using composite membranes of heteropolyacid (HPA)/polysulfone (PSF), HPA/sulfonated polysulfone (SPSF) for use in proton exchange membrane fuel cells (PEMFC) was investigated. PSF and its sulfonated polymer, SPSF was solution‐blended with phosphotungstic acid, a commercially available HPA. Fourier transform infrared (FTIR) spectroscopy of the HPA–40/SPSF composite exhibited band shifts showing a possibility of intermolecular hydrogen bonding interaction between the HPA additive and the sulfonated polymer. The composite membranes exhibited improved mechanical strength and low water uptake. The conductivity of the composite membrane, HPA–40/SPSF, consisting of 40 wt % HPA and 60 wt % SPSF [with a degree of Sulfonation (DS) of 40%] exhibited a conductivity 0.089 S/cm at room temperature that linearly increased upto 0.14 S/cm at 120 °C, whereas the widely used commercial membrane Nafion 117, exhibited a room temperature conductivity of 0.1 S/cm that increased to only 0.12 S/cm at 120 °C. In contrast, the composite of HPA–40/PSF exhibited a proton conductivity of 0.02 S/cm at room temperature that increased only to 0.07 S/cm at a temperature of 100 °C. The incorporation of HPA into SPSF not only rendered the membranes suitable for elevated temperature operation of PEMFC but also provides an inexpensive alternative compared to Nafion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1538–1547, 2005     

磷酸掺杂的ab-PBI膜及其在高温质子交换膜燃料电池中的应用

以3,4-二氨基苯甲酸为单体合成了ab-聚苯并咪唑.研究了磷酸掺杂的该质子交换膜在80-200℃,不同湿度以及不同酸掺杂量下的质子电导率.该质子交换膜可作为燃料电池的膜电解质,在常压不增湿的条件下,可使电池运行温度达到200℃.     

新型聚苯并咪唑树脂的微波合成及质子交换膜的性能

采用微波合成法,调整己二酸和2,6-吡啶二甲酸2种二酸单体的配比,使其与联苯四胺进行三元共聚,制备出一系列新型含脂肪链结构的聚苯并咪唑(PBI)类质子交换膜,并用红外光谱、热重分析进行了表征,对膜的吸水率、溶胀率、质子传导率、机械强度及抗氧化性能等进行了测试.当己二酸与2,6-吡啶二甲酸的摩尔比为3∶2时,所制备的PBI-C2膜掺杂磷酸后在160℃下的质子传导率可达30 mS/cm,拉伸强度在常温下可达77.54 MPa,断裂伸长率为39.25%,最大储能模量为9.0623 MPa,最大损耗模量为8.36 MPa,玻璃化转变温度为360℃,芬顿试验192 h后膜的降解率仅为0.21%,表明PBI-C2膜在高温质子交换膜燃料电池中具有较好的应用前景.     

PSF/SPSF高分子合金膜的膜材料对膜性能的影响

介绍了PSF与SPSF共混对合金膜的成膜性能和机械性能的影响 .二者共混改善了PSF的亲水性 ,提高了PSF膜的耐污染性 ,并且合金膜获得比PSF膜高的渗透通量     

Fabrication and optimization of proton conductive polybenzimidazole electrospun nanofiber membranes

Phosphoric acid (PA)–doped polybenzimidazole (PBI) proton exchange membranes have received attention because of their good mechanical properties, moderate gas permeability, and superior proton conductivity under high temperature operation. Among PBI‐based film membranes, nanofibrous membranes withstand to higher strain because of strongly oriented polymer chains while exhibiting higher specific surface area with increased number of proton‐conducting sites. In this study, PBI electrospun nanofibers were produced and doped with PA to operate as high temperature proton exchange membrane, while changes in proton conductivity and morphologies were monitored. Proton conductive PBI nanofiber membranes by using the process parameters of 15 kV and 100 μL/h at 15 wt% PBI/dimethylacetamide polymer concentration were prepared by varying PA doping time as 24, 48, 72, and 96 hours. The morphological changes associated with PA doping addressed that acid doping significantly caused swelling and 2‐fold increase in mean fiber diameter. Tensile strength of the membranes is found to be increased by doping level, whereas the strain at break (15%) decreased because of the brittle nature of H‐bond network. 72 hour doped PBI membranes demonstrated highest proton conductivity whereas the decrease on conductivity for 96‐hour doped PBI membranes, which could be attributed to the morphological changes due to H‐bond network and acid leaking, was noted. Overall, the results suggested that of 72‐hour doped PBI membranes with proton conductivity of 123 mS/cm could be a potential candidate for proton exchange membrane fuel cell.     

基于半互穿聚合物网络的高温质子交换膜的制备

通过构筑基于含不饱和双键的磺化聚芳醚酮(Allyl-SPAEK)与芳醚型聚苯并咪唑(PBI)的半互穿聚合 物网络(IPN), 获得综合性能优异的可用于高温质子交换膜燃料电池的PBI/Allyl-SPAEK复合膜材料. 在对 Allyl-SPAEK和PBI的分子进行设计和合成的基础上, 采用溶液共混-浇铸方法, 基于UV辐照交联, 获得了由丙烯基生成的共价键和咪唑基-磺酸基形成的强酸碱相互作用组成的IPN新体系, 并系统研究了新型复合膜的热、 机械性能和质子传导率. 结果表明, 具有PBI/Allyl-SPAEK半互穿聚合物网络的复合膜具有较高的质子 传导率和力学性能, 在同等磷酸吸附水平和测试条件下优于PBI膜. 在磷酸吸附水平为13.0左右时, PBI/ Allyl-SPAEK复合膜的最大拉伸强度达到12.1 MPa, 杨氏模量达到131.5 MPa, 是同等磷酸吸附水平下 PBI 膜的2.04倍. 在200 ℃时, 两种PBI/Allyl-SPAEK复合膜的质子传导率均达到 200 mS/cm以上, 比PBI膜传导率提高了38%.     

SPEEK-zirconium hydrogen phosphate composite membranes with low methanol permeability prepared by electro-migration and in situ precipitation

Sulfonated poly(ether ether ketone) (SPK)-zirconium hydrogen phosphate (ZrP) composite membranes were prepared by electro-driven migration of Zr(4+) and simultaneous in situ precipitation of ZrP using phosphoric acid under different electrical gradient, in order to avoid loss in its mechanical stability. Degree of sulfonation was estimated from (1)H NMR and ion-exchange capacity study that was found to be 61% and 57%, respectively. In this method Zr(4+) and HPO(4)(2-) were allowed to diffuse within the pores/channels of the preformed SPK membrane under given electrical gradient and ZrP was precipitated within the membrane matrix. ZrP loading density was measured as a function of applied electrical gradient for a definite reaction time (4 h) and electrolytic environment. Membranes with varied ZrP loading densities were characterized for their thermal and mechanical stabilities, physicochemical and electrochemical properties using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), water content, proton conductivity and methanol permeability. No loss in thermal and mechanical stability of membranes was observed due to incorporation of inorganic component (ZrP) in the membrane matrix. Although the composite membranes exhibited low proton conductivity in comparison to SPK membrane at room temperature, but the presence of the inorganic particles led to an improvement in high temperature conductivity. Selectivity parameter of these composite membranes was estimated at two temperatures namely 30 and 70 degrees C, in latter case it was found significantly higher than that for Nafion membrane (0.79 x 10(5) S s cm(-3)) under similar experimental conditions.     

Comparison of Electrochemical Synthesis of Ammonia by Using Sulfonated Polysulfone and Nafion Membrane with Sm1.5Sr0.5NiO4

Polysulfone (PSF) and sulfonated polysulfone (SPSF) were synthesized and characterized by IR spectrum. Sm_1.5Sr_0.5NiO₄ (SSN) and Ni‐Ce_0.8Sm_0.2O_2?δ (Ni‐SDC, Ni‐samarium doped ceria) were prepared and characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was synthesized from wet hydrogen and dry nitrogen with applied voltage, using SSN as cathode, Ni‐SDC as anode, Nafion and SPSF as proton membrane respectively. The performances of Nafion and SPSF membranes in ammonia synthesis were investigated and compared at atmospheric pressure and low temperature (25–100°C). The results demonstrated that the proton conducting performances of Nafion and SPSF membranes were similar and the highest rates of evolution of ammonia were up to 1.05×10^?8 and 1.03×10^?8 mol·cm^?2·s^?1 respectively at 80°C and 2.5 V.     

Structure-property interplay of proton conducting membranes based on PBI5N, SiO2-Im and H3PO4 for high temperature fuel cells

Polybenzimidazoles (PBIs) are among the polymers of choice to prepare membranes for high temperature polymer fuel cells. Poly-2,2'(2,6-pyridine)-5,5'-bibenzimidazole (PBI5N), doped with H(3)PO(4), and acid-doped PBI5N containing 10 wt% of imidazole-functionalized silica membranes were studied with thermogravimetric analysis, differential scanning calorimetry, dynamic-mechanical analysis, infrared spectroscopy, and broadband electric spectroscopy to examine the structure-property relationships. Key results show that: (1) doped PBI5N membranes show thermal decomposition starting at 120 °C, while pristine PBI5N is stable up to 300 °C; (2) the presence of filler increases the acid uptake and decreases the crystallinity of PBI5N; (3) the addition of phosphoric acid reduces the mechanical properties of the membrane, while the addition of filler has the opposite effect; (4) acid-doped membranes have conductivity values on the order of 10(-2)-10(-3) S cm(-1); and (5) membranes exhibit a Vogel-Tamman-Fulcher (VTF) type proton conduction mechanism, where proton hopping is coupled with the segmental motion of the polymer chain. Infrared spectroscopy combined with DFT quantum mechanical calculations was used to assign the experimental spectrum of PBI5N.     

Nafion/PTFE and zirconium phosphate modified Nafion/PTFE composite membranes for direct methanol fuel cells

We prepared Nafion/PTFE (NF) and zirconium phosphate (ZrP) hybridized Nafion/PTFE composite membranes (NF–ZrP). NF–ZrP composite membranes were prepared via two processes. One is impregnating sub-μm porous PTFE membrane directly in a Nafion/ZrOCl₂ solution (NF–Zr–d). The other is impregnating sub-μm porous PTFE membrane in a Nafion solution to prepare NF composite membrane, and then the NF membrane was impregnated in a ZrOCl₂ aqueous solution via in situ precipitation method (NF–Zr–I). The ZrOCl₂ inserted in NF composite membranes was then reacted with phosphoric acid to form ZrP and thus NF–ZrP–d and NF–ZrP–I composite membranes were obtained. The direct methanol fuel cell (DMFC) performances of membrane electrode assemblies prepared from Nafion-117, NF, NF–ZrP–d, and NF–ZrP–I composite membranes were investigated. The effects of introducing sub-μm porous PTFE film and ZrP particles into Nafion membranes on the DMFC performance were investigated. The influence of ZrP hybridizing process into NF membranes (the process of preparing NF–ZrP–I is inserting ZrOCl₂ into NF membranes after Nafion is annealed and the process of preparing NF–ZrP–d is mixing ZrOCl₂ into a Nafion solution before Nafion is annealed) on the morphology of NF–ZrP composite membranes and thus on the DMFC performance was also discussed.