Nanoporous composite, low cost, protonic membranes for direct methanol fuel cells

New types of nanoporous, composite membranes, prepared by readapting a procedure successfully used in the lithium battery technology, are here described and evaluated. The membranes are based on a polyvinylidene fluoride polymer matrix containing dispersed SiO2 ceramic powder at nanoparticles size. The unique preparation method confers an extended porosity which favors the swelling of the acid solutions to provide a high proton conductivity. The properties of these membranes can be monitored by properly controlling the amount of the dispersed ceramic filler, to finally obtain samples which combine good conductivity with low methanol permeability. Due to these features, the selected membrane samples can be profitably used as separators in ambient temperature direct methanol fuel cells, DMFCs.