Nafion/PTFE composite membranes for fuel cell applications

Porous polytetrafluoroethylene (PTFE) membranes were used as support material for Nafion((R))/PTFE composite membranes. The composite membranes were synthesized by impregnating porous PTFE membranes with a self-made Nafion solution. The resulting composite membranes were mechanically durable and quite thin relative to traditional perfluorosulfonated ionomer membranes (PFSI); we expect the composite membranes to be of low resistance and cost. In this study, we used three kinds of porous PTFE films to prepare Nafion/PTFE composite membranes of different thickness. Scanning electron micrographs and oxygen permeabilities showed that Nafion resin is distributed uniformly in the composite membrane and completely plug the micropores, there is a continuous thin Nation film present on the PTFE surface. The variation in water content of the composite and Nafion 115 membranes with temperature was determined. At the same temperature, water content of the composite membranes was smaller than that of the Nafion 115. In both dry and wet conditions, maximum strength and break strength of C-325(#) and C-345(#) were larger than those of Nafion 112 due to the reinforcing effect of the porous PTFE films. And the PEMFC performances and the lifetime of the composite membranes were also tested on the self-made apparatus. Results showed that the bigger the porosity of the substrate PTFE films, the better the fuel cell performance; the fuel cell performances of the thin composite membranes were superior to that of Nation 115 membrane; and after 180 h stability test at 500 mA/cm(2), the cell voltage showed no obvious drop. (C) 2002 Published by Elsevier Science B.V.

Stripping voltammetric determination of Pb(II) and Cd(II) based on the multiwalled carbon nanotubes-Nafion-bismuth modified glassy carbon electrodes

In this work, a new method for the simultaneous determination of Pb(II) and Cd(II) on the multiwalled carbon nanotubes (MWNT)-Nafion-bismuth modified glassy carbon electrode (GCE) using square-wave anodic stripping voltammetry has been studied. Scanning electron microscopy was used to investigate the characteristics of the MWNT-Nafion-bismuth modified GCE.

Surface-modified Nafion membranes with mesoporous SiO2 layers via a facile dip-coating approach for direct methanol fuel cells

In this study. Nafion (R) 117 membrane is surface-modified with mesoporous silica layers through in situ surfactant-templated sol-gel reaction. The reaction makes use of tetraethyl orthosilicate (TEOS) under acidic condition via dip-coating technique on both sides. Scanning electron microscopy (SEM), Fourier transformation infrared (FTIR), and thermogravimetric analysis (TGA) are employed to characterize the resultant membranes. Proton conductivity and methanol permeability of the membranes are also studied.

Unique electrochemiluminescence behavior of Ru(bpy)(3)(2+) in a gold/Nafion/Ru(bpy)(3)(2+) composite

The unique electrochemiluminescence (ECL) behavior of tris(bipyridine) ruthenium(II) (Ru(bpy)(3)(2+) immobilized in a gold/Nafion/Ru(bpy)(3)(2+) composite material was investigated. In this composite, the Ru(bpy)(3)(2+) ECL was found mainly occurred at 0-0.4 V during the cathodic scan process and the ECL peak was at about 0.1 V, which was quite different to the reported Ru(bpy)(3)(2+) ECL. Similar to the generally observed Ru(bpy)(3)(2+) ECL, the present ECL also could be enhanced by tri-n-propylarnine (TPA). It is also unique that in the presence of TPA, another ECL peak at about 0.38 V occurred.

Electrochemiluminescence from tris(2,2 '-bipyridyl)ruthenium(II)-graphene-Nafion modified electrode

An electrochemiluminescence (ECL) sensor based on Ru(bpy)(3)(2+)-graphene-Nafion composite film was developed. The graphene sheet was produced by chemical conversion of graphite, and was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. The introduction of conductive graphene into Nafion not only greatly facilitates the electron transfer of Ru(bpy)(3)(2+), but also dramatically improves the long-term stability of the sensor by inhibiting the migration of Ru(bpy)(3)(2+) into the electrochemically inactive hydrophobic region of Nafion. The ECL sensor gives a good linear range over 1 x 10(-7) to 1 x 10(-4) M with a detection limit of 50 nM towards the determination of tripropylamine (TPA), comparable to that obtained by Nafion-CNT.

聚氨基黑10B/Nafion修饰电极上多巴胺的检测

用电化学聚合法制备了聚氨基黑10B/Nafion修饰电极,利用循环伏安法研究了多巴胺在此修饰电极上的电化学行为。在磷酸盐缓冲溶液(pH6.0)中,多巴胺在修饰电极上呈现可逆的氧化还原峰。其峰电位都随pH值的增加而负移。多巴胺氧化还原峰电流与其浓度在0.2～30μmol/L范围内呈良好的线性关系;检出限为1.0×107mol/L。实验结果表明:本修饰电极具有良好的重现性、稳定性和较强的抗干扰能力。将此修饰电极用于多巴胺注射液和小牛血清中多巴胺的检测,结果令人满意。

Implantation of Nafion (R) ionomer into polyvinyl alcohol/chitosan composites to form novel proton-conducting membranes for direct methanol fuel cells

A series of cost-effective, proton-conducting composite membranes, comprising of Nafion (R) ionomer, chitosan (CS). and polyvinyl alcohol (PVA), is successfully prepared. By taking advantage of the strong electrostatic interactions between Nafion (R) ionomer and CS component, Nafion ionomer is effectively implanted into the PVA/CS composite membranes, and improves proton conductivity of the PVA/CS composite membranes. Furthermore, this effect dramatically depends on the composition ratio of PVA/CS, and the optimum conductivity is obtained at the PVA/CS ratio of 1:1. The developed composite membranes exhibit much lower methanol permeability compared with the widely used Nafion (R) membrane, indicating that these novel membranes have great potential for direct methanol fuel cells (DMFCs).

Direct electron transfer and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified with Nafion and mesoporous carbon FDU-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified with mesoporous carbon FDU-15 (MC-FDU-15) and Nafion by simple technique. The sorption behavior of GOD immobilized on MC-FDU-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that MC-FDU-15 could facilitate the electron exchange between the active center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and MC-FDU-15 matrices display direct, reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 4.095 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Nafion-graphene nanocomposite film as enhanced sensing platform for ultrasensitive determination of cadmium

In this work, an ultrasensitive platform for the detection of cadmium (Cd2+) combining the nafion-graphene nanocomposite film with differential pulse anodic stripping voltammetry (DPASV) analysis was presented. It is found that this sensing platform exhibits enhanced response to the determination of the Cd2+ and has been used to determine the Cd2+ in real sample with good recovery.

Solid-state electrochemiluminescence sensor based on the Nafion/poly(sodium 4-styrene sulfonate) composite film

An effective electrochemiluminescence (ECL) sensor based on Nafion/poly(sodium 4-styrene sulfonate) (PSS) composite film-modified ITO electrode was developed. The Nafion/PSS/Ru composite film was characterized by atomic force microscopy, UV-vis absorbance spectroscopy and electrochemical experiments. The Nafion/PSS composite film could effectively immobilize tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) via ion-exchange and electrostatic interaction. The ECL behavior of Ru(bpy)(3)(2+) immobilized in Nafion/PSS composite film was investigated using tripropylamine (TPA) as an analyte. The detection limit (S/N = 3) for TPA at the Nafion/PSS/Ru composite-modified electrode was estimated to be 3.0 nM, which is 3 orders of magnitude lower than that obtained at the Nafion/Ru modified electrode. The Nafion/PSS/Ru composite film-modified indium tin oxide (ITO) electrode also exhibited good ECL stability. In addition, this kind of immobilization approach was simple, effective, and timesaving.

High-sensitivity determination of lead and cadmium based on the Nafion-graphene composite film

Graphene nanosheets, dispersed in Nafion (Nafion-G) solution, were used in combination with in situ plated bismuth film electrode for fabricating the enhanced electrochemical sensing platform to determine the lead (Pb2+) and cadmium (Cd2+) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the composite film modified glassy carbon electrode were investigated. It is found that the prepared Nafion-G composite film not only exhibited improved sensitivity for the metal ion detections, but also alleviated the interferences due to the synergistic effect of graphene nanosheets and Nafion. The linear calibration curves ranged from 0.5 mu g L-1 to 50 mu g L-1 for Pb2+ and 1.5 mu g L-1 to 30 mu g L-1 for Cd2+. respectively. The detection limits (S/N = 3) were estimated to be around 0.02 mu g L-1 for Pb2+ and Cd2+. The practical application of the proposed method was verified in the water sample determination.