DMFCs用磺化聚醚醚酮/功能化二氧化硅复合质子交换膜

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.

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

The present paper focuses on improving the water-holding ability of sulfonated poly(ether ether ketone)(SPEEK)(degree of sulfonation,DS = 55.1%) membranes.Functionalized silica(silica sol(SiO2) and silica powder with sulfonic acid groups(SiOx-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/SiOx-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 2.6×10-4 S·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 Nafion 115.DMFCs single cell performance of SPEEK/SiO2(20 wt%) and SPEEK/SiOx-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.