Clean Technology 2007
S.-Y. Ryu, J.-D. Jeon and S.-Y. Kwak
Seoul National Univesity, KR
Nafion, microporous titaniumsilicate, ETS-4, proton conductivity
Nafion is currently the most frequently used polymeric electrolyte in membranes for many fuel cell applications. Direct methanol fuel cells this electrolyte membrane are currently being considered as a desirable electrochemical power source in potable applications. However, commercialization of the DMFCs prepared using Nafion membranes is inhibited by a major technical problem. Typical Nafion membranes are permeable to methanol transport, thereby significantly reducing fuel utilization efficiency of the fuel cell. In order to diminish the methanol permeation through the membrane, Nafion/microporous titaniumsilicte (ETS-4) composite membranes were prepared. The ETS-4 molecular sieves will play a role as size-slective adsorbent because their pore size has smaller than diameter of methanol and bigger than that of water. The ETS-4 was synthesized by the hydrothermal method using gels of the following molar compositions; 5 H2O2 : 0.5 TiO2 : 10 SiO2 : 18 NaOH : 675 H2O. The water uptake of composite membranes increased from 21.4% (IEC = 0.89 meq/g for pure Nafion) to 32.2% (IEC = 0.72 meq/g for 80wt%Nafion/20wt%ETS-4) with increases in the ETS-4 content. However, their proton conductivities gradually decreased with increase of the amount of ETS-4 in the membranes due to decrease of IEC values.