Transport behavior of proton and methanol in SPEEK/Cloisite 15A/TAP composite membranes at varies temperature

Abstract

The investigation on the transport behavior of proton and methanol in sulfonated polyether ether ketone (speek) composite membrane under various temperatures (room temperature to 80°c)has been conducted. the speek/closite 15a/tap composite membranes were prepared via solution intercalation method. the resulting membranes were characterized by evaluating their physicochemical properties in terms of water uptake, proton conductivity and methanol permeability prior to direct methanol fuel cell application. it was found that the proton conductivity and methanol permeability of the composite membranes increased with the rise of temperature. the highest selectivity valueof 9.6 xlo4 sscm'3of speek/cloisite 15a/tap membrane was recorded at 60°cwith the proton conductivity o f 7.87 xlo'3scm‘‘ and 4.88xl0‘7cmi s'1 methanol permeability which was higher compared to nafion 117 membrane which was only 3.4xl04 sscm'3. this was mainly contributed by the methanol permeability which was found to be lower than that o f nafion 117 membranes at all investigated temperatures. speek/cloisite 15a/tap composite membrane exhibited higher activation energy, e,(15.9 kj/mol) in comparison to the nafion 117 membrane (9.20 kj/mol). the e, value of the composite membrane was in agreement with the e, for proton transport mechanism (vehicle and grotthus) which is in the range of 14-40 kj/mol therefore, it can be concluded that the proton transport in the composite membrane is contributed by both hopping and vehicle mechanisms and the protons travel a direct path through both polymer and inorganic fillers phase, while methanol has more tortuous path around the cloisite 15a particles with the increasing of temperature.