Study On Preparation And Properties Of PWA-d-PVA/PVDF Proton Exchange Membrane By In-situ Syntheticism For Applications

Direct methanol fuel cell is the new energy saving battery of21st century environmental protection and has gained much attention. As a new generation of high efficiency energy have the characteristics of rapid start-up at low temperature, environmental compatibility and simple integrated structure. In recent years, attention has been focused on the research of inorganic-organic hybrid membranes. The organic chains provide the required specific properties, such as flexibility, proton conductivity and the inorganic backbone of the hybrid increase the thermal stability of the membranes. Polyvinyl alcohol (PVA) become recognized as a basal material of polymer membrane due to the advantage of good resistance alcohol, low price and easy to form membrane. Via adding inorganic component into the PVA can obtain high proton conductivity, but the degree swelling of membrane is bigger.In order to improve membrane swelling degree and methanol permeability, PVA/PVDF doped phosphotungstic acid (PWA) proton exchange membranes were prepared by in-situ synthesis which used organic polar solvent instead of water solution in this work. The mechanical properties of PWA-d-PVA/PVDF membranes were investigated by the multi-functional material experiment machine. The influences of contents of PVDF, Na2WO4and H3PO4on the proton conductivity, swelling and methanol permeability were studied by AC impedance spectroscopy and gas chromatograph. The results showed that the proton exchange membrane have the excellent performances when the content of Na2WO4is10%, H3PO4is10%and PVDF is20%. The properties of membrane as follows: the proton conductivity of membrane is0.015S/cm;Compared with Nafion membrane, the methanol permeability of PWA-d-PVA/PVDF membrane is9.21×10-7cm2/s and decreased nearly one order of magnitude; The swelling degree of PWA-d-PVA/PVDF membrane is only12.2%, compared with Nafion membrane reduced23.8%. The thermal stability and microtopography of the membranes were characterized by TG and SEM. The results indicated that the thermal stability obviously improve of proton exchange membrane, the membrane have the excellent thermal stability between0~155℃. In addition, the phosphotungstic acid and PVDF are uniformly distribute in the membrane and have the better compatibility with PVA, because of there isn’t reunion in the membrane.The PWA-d-PVA/PVDF membrane assembled into direct methanol fuel cell (DMFC) for battery performance test. The membrane was measured in the methanol concentration is2M of DMFC and the result show that the power density is12.48mw/cm2, compared with Nafion115membrane maximum power density increased by18.29%.