Spectroscopic investigations into degradation of polymer membranes for fuel cells applications

The research was focused on synthesis of proton conductive, easily degradable polymer membranes, which can be used as a model system to verify the efficiency of transition metal ions (TMI) in prevention of polymer degradation. Two polymers composed of 2-hydroxyethyl methacrylate (HEMA), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), and styrenesulfonic acid (SS) were synthesized. The copolymers were characterized by gel permeation chromatography (GPC), elementary analysis, and FTIR and fluorescence spectroscopies. The results allowed determination of weight-average molecular weight and the copolymer composition. The protons of sulfonic groups were substituted by paramagnetic transition metal ions of various spin states (Cr(3+), S=3/2 and Mn(2+), S=5/2) with the loading varying from 0.5 up to 10 mol%. The effectiveness of spin catalysis was checked by EPR. The results obtained indicate enhancement of polymer stability in the presence of Mn(2+).     

Improvement in performance of a direct ethanol fuel cell: Effect of sulfuric acid and Ni-mesh

A direct ethanol fuel cell (DEFC) is developed with low catalyst loading at anode and cathode compared to that reported in the literature. Pt/Ru (40%:20% by wt.)/C and Pt-black were used as anode and cathode catalyst with loadings in the range of 0.5–1.2 mg/cm². The temperatures of anode and cathode were varied from 34 °C to 110 °C, and the pressure was maintained at 1 bar. Although low catalyst loading was used, the cell performance is enhanced by 40–50% with the use of low concentration of sulfuric acid in ethanol and Ni-mesh as current collector at the anode. The power density 15 mW/cm² at 32 mA/cm² of current density is obtained from the single cell with 0.5 mg/cm² loading of Pt–Ru/C at anode (90 °C) and Pt-black at cathode (110 °C). The performance of DEFC increases with the increase in ethanol and sulfuric acid concentrations, electrocatalyst loadings up to 1 mg cm⁻² at anode and cathode. However, the performance of DEFC decreases with further increase in electrocatalyst loading.     

Preliminary simulation studies on a cylindrical PEM scanner using GATE

In this paper, we investigate the performance of a cylindrical positron emission mammography （PEM） by simulation, in order to estimate its feasibility before implementation. A well-developed simulation package, Geant4 Application for Tomographic Emission （GATE）, is used to simulate the scanner geometry and physical processes. The simulated PEM scanner is composed of 64 blocks axially arranged in 4 rings with an axial field-of-view （AFOV） of 12.8 cm and 16.6 cm in diameter. For each block, there is a 16×16 array of 2 mm×2 mm×15 mm lutetium yttrium oxyorthosilicate （LYSO） crystals. In the simulated measurements, the spatial resolution is at the center of the FOV of 1.73±0.07 mm （radial） and 1.81±0.08 mm （tangential）, but of 4.83±0.09 mm （radial） and 4.37±0.07 mm （tangential） while 5 cm off the center. The central point source sensitivity （ACS） is 4.04% （1.50 Mcps/mCi） at an energy window of 350-650 keV. Moreover, the capillary and cylindrical sources are simulated coupled to breast phantoms for the scatter fraction （SF） and Noise Equivalent Count Rate （NECR） test. For a breast phantom with a 350-650 keV energy window, SF may reach the highest 32.95%, while NECR is degraded down to the lowest 255.71 kcps/mCi. Finally, we model a breast phantom embedded with two spheres of different activities. The reconstructed image gives good results despite a bit of difference in image contrast. Further, the image quality will be improved by scatter and random correction. All these test results indicate the feasibility of this PEM system for breast cancer detection.     

Synthesis and Characterization of Novel Sulfonated Hybrid Congo Red Membranes from Chlorofunctionalized Silsesquioxanes for Fuel Cell Application

A new sulfonated copolymers containing congo red groups were synthesized as a potential electrolyte for high temperature PEFCs. The resulting cross-linked sulfonated hybrid congo red membranes showed greatly improved water stability in comparison with the uncrosslinked ones while high proton conductivity was maintained. sulfonated membranes have been tested with respect to fuel cell performance. Short term fuel cell test for 100 hr gave a stable performance. These membranes are less expensive compared to Nafion. New sulfonated proton exchange composites membranes were used biological fuel cells. Molasses which is the waste of sugar factory, was used in anode as fuel and different bacteria species was sowing. Potential change was reported in biological fuel cells.     

Science and technology of perfluorocyclobutyl aryl ether polymers

This article highlights the preparation of perfluorocyclobutyl (PFCB) aryl ether polymers for a multitude of commercial technologies that are of academic and commercial global interest. In this account, the synthesis of various aryl trifluorovinyl ether (TFVE) monomers tailored for specific applications is discussed. The preparation of PFCB aryl ether polymers and their properties is then presented. Topics of PFCB aryl ether polymers and their applications include photonics, polymer light emitting diodes (PLEDs), proton exchange membranes (PEMs) for fuel cells, atomic oxygen (AO) resistant coatings, and hybrid composites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5705–5721, 2007     

Studies on synthesis and property of novel acid-base proton exchange membranes

Sulfonated poly(phthalazinone)s (SPPENK, SPPESK and SPPBEK) were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide (PEI) as the basic compounds, casting from their N-methylpyrrolidone (NMP) solution directly onto clean glass plates at 60℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity (IEC).     

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℃.     

缓蚀剂对铜作用的激光扫描微区光电化学研究

采用激光扫描微区光电化学显微技术(PEM)对不同浓度下的苯并三氮唑(BTA)及其衍生物4-羧基苯并三唑甲酯与5-羧基苯并三唑甲酯的混合物(CBTME)在硼砂缓冲溶液(pH9.2)中对铜电极的缓蚀作用作了比较研究。研究发现当电位正向扫描至某一电位时,一定浓度的BTA或CBTME作用下,铜电极光响应由p-型转化为n-型,并可依此判断缓蚀剂的缓蚀性能,n-型光响应越大,缓蚀剂的缓蚀性能越好,与循环伏安光电流及交流阻抗测试的结果相一致;实验还发现,影响缓蚀剂对铜作用的过程不仅与缓蚀剂本身有关,还与电极电位有关。在一定的电位与一定的缓蚀剂浓度下可观察到铜电极表面共存着p-型和n-型区域及p转n的过程,因此可从微观上观察到缓蚀剂与铜表面作用的过程,为缓蚀剂的应用建立了良好的理论基础。     

Development of Poly(Vinyl Alcohol)-Based Polymers as Proton Exchange Membranes and Challenges in Fuel Cell Application: A Review

Abstract

Poly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive proton exchange membrane (PEM) alternative to Nafion^TM. However, the pristine PVA membrane is a poorer proton conductor than the Nafion^TM membrane due to the absence of negatively charged ions. Hence, modification of PVA matrixes whilst complying with the requirements of projected applications has been examined extensively. Generally, three modification methods of PVA membranes have been highlighted in previous reports, and these are (1) grafting copolymerization, (2) physical and chemical crosslinking, and (3) blending of polymers. The use of each modification method in different applications is reviewed in this study. Although the three modification methods can improve PVA membranes, the mixed method of modification provides another attractive approach. This review covers recent studies on PVA-based PEM in different fuel cell applications, including (1) proton-exchange membrane fuel cells and (2) direct-methanol fuel cells. The challenges involved in the use of PVA-based PEM are also presented, and several approaches are proposed for further study.     

Modeling,shape analysis and computation of the equilibrium pore shape near a PEM–PEM intersection

In this paper we study the equilibrium shape of an interface that represents the lateral boundary of a pore channel embedded in an elastomer. The model consists of a system of PDEs, comprising a linear elasticity equation for displacements within the elastomer and a nonlinear Poisson equation for the electric potential within the channel (filled with protons and water). To determine the equilibrium interface, a variational approach is employed. We analyze: (i) the existence and uniqueness of the electrical potential, (ii) the shape derivatives of state variables and (iii) the shape differentiability of the corresponding energy and the corresponding Euler–Lagrange equation. The latter leads to a modified Young–Laplace equation on the interface. This modified equation is compared with the classical Young–Laplace equation by computing several equilibrium shapes, using a fixed point algorithm.