New highly proton-conducting membrane poly(vinylpyrrolidone)(PVP) modified poly(vinyl alcohol)/2-acrylamido-2-memyl-l-propanesulfonic acid (PVA-PAMPS) for low temperature direct methanol fuel cells (DMFCs)

摘要

A new type of chemically cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA),2-acrylamido-2-methyl-l-propanesulfonic acid (PAMPS) and poly(vinylpyrrolidone) (PVP) have been prepared and evaluated as proton conducting polymer electrolytes.The proton conductivity (sigma) of the membranes was investigated as a function of cross-linking time,blending composition,water content and ion exchange capacity (IEC).Membranes were also characterized by FT-IR spectroscopy,thermogravimetric analysis (TGA),and the differential scanning calorimetry (DSC).Membrane swelling decreased with cross-linking time,accompanied by an improvement in mechanical properties and a small decrease in proton conductivity due to the reduced water absorption.The membranes attained 0.088 S cm~(-1) of the proton conductivity and 1.63 mequiv g~(-1) of IEC at 25+-2degC for a polymer composition PVA-PAMPS-PVP being 1:1:0.5 in mass,and a methanol permeability of 6.1 X 10~(-7) cm~2 s~(-1),which showed a comparable proton conductivity to Nafion 117,but only one third of Nafion 117 methanol permeability under the same measuring conditions.The membranes displayed a relatively high oxidative durability without weight loss of the membranes (e.g.100 h in 3% H_2O_2 solution and 20 h in 10% H_2O_2 solution at 60degC).PVP,as a modifier,was found to play a crucial role in improving the above membrane performances.