Modification of Ce(SO4)2 on Phosphosilicate Gels used as Proton Conductors

Preparation of proton conductors with good chemical durability and high proton conductivity is prerequisite for increasing efficiency of medium temperature fuel cells. In this research, new type of proton conductors were synthesized by adding Ce(SO4)2 to the phosphosilicate gels through sol-gel process. The results prove that adding Ce(SO4)2 can apparently increase proton conductivity of the gels, which reaches the maximum conductivity with the Ce(SO4)2 content of 0.81%, i.e. |мSUB>100=1.25S/m, |мSUB>130=2.11S/m. These values are 70% higher than those without adding Ce(SO4)2. The proton conductivity of the gels will decrease by 20% in dry argon atmosphere, that is, |мSUB>100=1.06S/m, |мSUB>130=1.68S/m. Thermal analysis reveals that introduction of Ce(SO4)2 results in an increase in water-retention ability of the gels. Furthermore, NMR spectra indicate that there forms more PO43- isolated phosphate structure units containing no bridgea2oxygen (Q0) and Q1 structure units containing one bridgea2oxygen like Si aO aP and P aO aP in the Ce(SO4)2-containing gels. These structure units are favorable to proton transportation, which increase the proton conductivity of the gels.