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A sulfonated poly(ether ether ketone)(SPEEK) membrane with a fairly high degree of sulfonation(DS) can swell excessively and even dissolve at high temperature.To solve these problems,insolvable functionalized silica powder with sulfonic acid groups(SiOx-S) was added into the SPEEK matrix(DS = 55.1%) to prepare SPEEK/SiOx-S composite membranes.The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder.Pure SPEEK membrane swelled 52.6% at 80°C,whereas the SPEEK/SiOx-S(15%,by mass) membrane swelled only 27.3% at the same temperature.From room temperature to 80℃,all SPEEK/SPEEK/SiOx-S composite membranes had methanol permeability of about o ne order of magnitude lower than that of Nafion?115.Compared with pure SPEEK membranes,the addition of the SiOx-S powder not only leads to higher proton conductivity,but also increases the dimensional stability at higher temperatures,and greater proton conductivity can be achieved at higher temperature.The SPEEK/SiOx-S(20%,by mass) membrane could withstand temperature up to 145°C,at which in 100% relative humidity(RH) its proton conductivity exceeded slightly that of Nafion?115 membrane and reached 0.17 S·cm-1,while pure SPEEK membrane dissolved at 90°C.The SPEEK/SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability,high proton conductivity,and low methanol permeability.
A sulfonated poly (ether ether ketone) (SPEEK) membrane with a fairly high degree of sulfonation (DS) can swell excessively and even dissolve at high temperature. To solve these problems, insolvable functionalized silica powder with sulfonic acid groups (SiOx-S) was added into the SPEEK matrix (DS = 55.1%) to prepare SPEEK / SiOx-S composite membranes. The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder SPEEK / SiOx-S (15% by mass) membrane swelled only 27.3% at the same temperature. Flash room temperature to 80 ° C, all SPEEK / SPEEK / SiOx- S composite membranes had methanol permeability of about o ne order of magnitude lower than that of Nafion® 115.Compared with pure SPEEK membranes, the addition of the SiOx-S powder not only leads to higher proton conductivity, but also increases the dimensional stability at higher temperatures, and greater proton conductiv ity can be achieved at higher temperature. The SPEEK / SiOx-S (20% by mass) membrane could withstand temperature up to 145 ° C, at which in 100% relative humidity (RH) its proton conductivity exceeded slightly that of Nafion? 115 membrane and reached 0.17 S · cm -1 while pure SPEEK membrane dissolved at 90 ° C. The SPEEK / SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.