DMFCs用磺化聚醚醚酮/功能化二氧化硅复合质子交换膜

PROTON EXCHANGE SULFONATED POLY(ETHER ETHER KETONE)/ FUNCTIONALIZED SILICA COMPOSITE MEMBRANES IN DMFCs

在磺化度(DS)为55.1%的磺化聚醚醚酮(SPEEK)中掺杂功能化二氧化硅(吸湿性SiO2溶胶及带有磺酸基团的二氧化硅(SiOx-S)粒子)制备SPEEK/SiO2和SPEEK/SiOx-S复合质子交换膜.SiO2和SiOx-S的掺杂能有效提高复合膜的抗溶胀、阻醇性能及高温低湿情况下的电导率.纯SPEEK膜在80℃溶胀为52.6%,而SiO2和SiOx-S掺杂量为15%的复合膜在此温度下分别仅有26.2%和27.3%的溶胀.在室温至80℃范围内,SPEEK/SiO2(20 wt%)和SPEEK/SiOx-S(20 wt%)复合膜的甲醇透过系数比Nafion115膜小近2个数量级.在120℃、相对湿度(RH)为40%情况下,SPEEK纯膜的电导率仅为2.6×10-4S.cm-1,SPEEK/SiO2(20 wt%)复合膜约为2.0×10-3S.cm-1,而SPEEK/SiOx-S(20 wt%)复合膜高达1.0×10-2S.cm-1,与Nafion115相当.SPEEK/SiO2(20 wt%)和SPEEK/SiOx-S(20 wt%)2种复合膜的尺寸稳定性较高,膜电极无催化剂与膜分离现象,其DMFCs单电池性能好于SPEEK膜.

The present paper focuses on improving the water-holding ability of sulfonated poly （ether ether ketone） （SPEEK） （degree of sulfonation, DS = 55. 1% ） membranes. Funetionalized silica （ silica sol （SiO2） and silica powder with sulfonic acid groups （SiO-S）） were chosen as the hygroscopic additive, respectively. SPEEK/SiO2, SPEEK/SiOx-S composite membranes were obtained by casting a homogeneous mixture of SiO2 （or SiOx-S） and SPEEK in N,N-dimethylacetamide onto glass plate and then evaporating the solvent at 60℃. The decrease in both the swelling degree and the methanol permeability and the improvement in the conductivity at a high temperature and a low humidity of the membranes were a dose-dependent result of addition of the SiO2 and SiOx-S powders. Pure SPEEK membranes swelled 52.6% at 80℃ , whereas the SPEEK/SiO2（15 wt%） and SPEEK/SiO-S （15 wt%） membranes swelled only 26.2% and 27.3% at the same temperature,respectively. From room temperature to 80℃ , SPEEK/SiO2 （20 wt% ） and SPEEK/SiOx-S （20 wt% ） membranes had methanol permeability of about two order of magnitude lower than that of Nafion 115. At 120℃ and 40% relative humidity （RH）,the conductivity of pure SPEEK membranes is only 2.6×10-4S·cm -1,and that of SPEEK/SiO2（20 wt%） membranes is about 2.0×10-3 S·cm-1,while that of SPEEK/SiOx-S （20 wt% ） composite membranes reaches 1.0×10-2 S·cm-1, which is close to that of Nafion115. DMFCs single cell performance of SPEEK/SiO2 （20 wt% ） and SPEEK/SiO -S （20 wt% ） membranes was better than that of pure SPEEK membranes because they had good dimensional stability and no separation of catalyzers and membranes in membrane electrode assembles.