A novel inorganic-organic composite membrane based on sulfonated polyether ether ketone(SPEEK) with embedded phosphotungstic acid(PWA) for direct methanol fuel cells(DMFC) was prepared. IR spectra results indicate that PWA was kept in SPEEK matrix as the Keggin structure. From SEM micrograph, it could be found that the solid PWA were well mixed with SPEEK matrix and showed no agglomeration in the membrane. Proton conductivity of the PWA/SPEEK composite membrane is higher than that of pure SPEEK membrane, and is similar or superior to that of Nafion ○R 115 membrane in the temperature range 80—110 ℃. Methanol permeability of the PWA/SPEEK membrane was considerably smaller than that of Nafion ○R 115 membrane. Because of its high conductivity and low methanol permeability, the PWA/SPEEK membrane seems to be an excellent candidate for DMFC applications.
In order to improve the property of sulfonated poly(pathalazinone ether ketone)(SPPEK)membrane of high sulfonation degree,proton conductor zirconium tricarboxybutylphosphonate[Zr(PBTC)]was used and incorporated into SPPEK to prepare Zr(PBTC)/SPPEK composite membranes for direct methanol fuel cell(DMFC).The results showed that the additive could reduce the water swelling and methanol permeability of membranes efficiently without sacrificing its conductivity.DMFC single cell performance demonstrated that the 30%(mass)Zr(PBTC)/SPPEK composite membrane was better than the pristine SPPEK membrane for its reduced swelling and consequently improved dimensional stability.
Proton conducting membranes composed of phosphotungstic acid (PWA) and poly(vinyl alcohol) (PVA)were prepared. Conductivity and Fourier transform infrared spectrometer(FTIR) measurements show that most ofthe acid embedded are stable in the PVA matrix when the membrane is immerged in water or methanol solution atroom temperature. Conductivity of the composite membranes scatters around 10-3 S.cm-1 at room temperature.The methanol crossover through the membranes is about an order of magnitude lower than that through Nafion117 membrane.
