Zhi-Gang Shao

Composite Nafion/polyvinyl alcohol membranes for the direct methanol fuel cell

Abstract The methanol crossover in the direct methanol fuel cell (DMFC) can be reduced by casting a thin film containing the mixture of polyvinyl alcohol (PVA) and Nafion on a commercial perfluorosulfonic membrane (Nafion, Dupont). In addition to the cell polarization testing, a design factor defined as the reciprocal of the multiplication of the methanol permeation current density and membrane area resistance, was used to evaluate the membrane’s performance. Our study has shown that at the weight ratio of 1:1 in PVA and Nafion, the thin film-coated Nafion membrane exhibits low methanol crossover and the membrane conductance can be improved by the sulfonation treatment.

Carbon nanotubes reinforced nafion composite membrane for fuel cell applications

A carbon nanotubes (CNTs) reinforced Nafion composite membrane for the H-2/O-2 fuel cell was developed. CNTs/Nafion composite membrane, in which CNTs were dispersed uniformly, was prepared by solution-casting. CNTs reinforced membranes, with the addition of a small amount of CNTs (1 wt %), showed excellent mechanical strength. The CNTs/Nafion composite membrane could also decrease dimensional change compared with the commercial Nafion membrane. The performance of the CNTs reinforced composite membrane (50 mu m) was almost the same as the cell prepared with commercial Nafion NRE-212 membrane. (c) 2006 The Electrochemical Society.

Self-Humidifying Cs2.5H0.5PW12O40 ∕ Nafion ∕ PTFE Composite Membrane for Proton Exchange Membrane Fuel Cells

A Cs2.5H0.5PW12O40/Nafion/polytetrafluoroethylene (PTFE) self-humidifying composite membrane was developed for proton exchange membrane fuel cells. It was prepared by recasting the Cs2.5H0.5PW12O40/Nafion self-humidifying layer onto the two sides of a Nafion/PTFE composite membrane with a solution-recast method. Due to the strong acidic, hydrophilic, and redox properties of Cs2.5H0.5PW12O40, the Cs2.5H0.5PW12O40/Nafion self-humidifying layer not only contributes to humidify the membrane but also contributes to the improvement of the open-circuit voltage of the fuel cell. When the self-humidifying composite membrane was employed as an electrolyte in H-2/O-2 PEMFC, a higher maximum power density value (1.1 W/cm(2)) was obtained than that of Nafion/PTFE composite membrane (0.6 W/cm(2)), under the operating conditions of 70 degrees C and at the humidified temperature of 20 degrees C. (c) 2005 The Electrochemical Society.

Nafion membrane coated with sulfonated poly(vinyl alcohol): Nafion film for direct methanol fuel cells

We report a Nafion 112 (DuPont)-based membrane containing a recast film made of sulfonated poly(vinyl alcohol) and Nafion composite for the direct methanol fuel cell (DMFC). Without a significant increase in the membrane resistance, this composite membrane demonstrates a reduction of the methanol permeation rate by as much as 48% when compared to the native Nafion. This membrane is mechanically robust and should be a suitable membrane electrolyte for the DMFC.

Quaternized poly(phthalazinone ether sulfone ketone) membrane doped with H3PO4 for high-temperature PEMFC operation

A quaternized poly(phthalazinone ether sulfone ketone) (qappesk) membrane doped with h3po4 was prepared and characterized. infrared and p-31 nmr spectra indicated that this membrane may have the same mode of conducting proton as polybenzimidazole (pbi) membrane doped with h3po4. the qappesk membrane doped with h3po4 showed high proton conductivity (0.072 s/cm at 150 degrees c), and good thermostability measured by thermogravimetric analysis. the peak power density of single cell with qappesk/h3po4 composite membrane and operated at 150 degrees c with dry h-2/o-2 reached 0.85 w/cm(2). these results show that qappesk/h3po4 composite membrane is promising for high-temperature proton exchange membrane fuel cell (pemfc) applications. (c) 2005 the electrochemical society.

Recycling and regeneration of used perfluorosulfonic membranes for polymer electrolyte fuel cells

This paper describes a method for the recycling and regeneration of used perfluorosulfonic Nafion® (Dupont) membranes by dissolution and recasting. The dissolution of the used Nafion® membranes from polymer electrolyte fuel cells is realized using dimethyl sulfoxide as a solvent under atmospheric pressure and 190 °C. A mechanically robust membrane can be reproduced by a recast process of the dissolved Nafion® solution at 170 °C. The recycled membrane has shown a good crystalline structure and high mechanical strength. Membrane properties, including water uptake, exchange capacity and resistance are similar to that of the as-received Nafion® 115 membrane. Fuel cells prepared by the recycled membrane demonstrate a comparable performance to that of the fresh fuel cell.

Tungsten trioxide hydrate incorporated Nafion composite membrane for proton exchange membrane fuel cells operated above 100 degrees C

A new composite membrane is fabricated by incorporating tungsten trioxide hydrate into Nafion to be employed as a candidate electrolyte for proton exchange membrane fuel cells (PEMFCs) operated above 100°C. Thermal behavior and proton conductivity of the composite membrane are studied by means of thermogravimetric/differential thermal analyis (TG/DTA) and AC impedance measurements, respectively. These results demonstrate that the thermal stability of the composite membrane has no appreciable change when compared with the native Nafion membrane. The proton conductivity of the composite membrane is found to be better than that of the native Nafion membrane at high temperature and lower relative humidity. When the composite membrane is used as an electrolyte in H2/O2 PEMFC under the operating conditions of 110°C, 1.36 atm gas pressure, and 70% relative humidity, the observed current density value at 0.4 V is 1.5 times higher than that of the cell employing native Nafion membrane as an electrolyte.