| Autor: |
Gomaa MM; Physics Department, Faculty of Science, Minia University, Minia P.O. Box 61519, Egypt., Sánchez-Ramos A; Department of Thermal and Fluids Engineering, Universidad Carlos III de Madrid, 28911 Leganes, Spain., Ureña N; Department of Materials Science and Engineering and Chemical Engineering, Universidad Carlos III de Madrid, 28911 Leganes, Spain., Pérez-Prior MT; Department of Materials Science and Engineering and Chemical Engineering, Universidad Carlos III de Madrid, 28911 Leganes, Spain., Levenfeld B; Department of Materials Science and Engineering and Chemical Engineering, Universidad Carlos III de Madrid, 28911 Leganes, Spain., García-Salaberri PA; Department of Thermal and Fluids Engineering, Universidad Carlos III de Madrid, 28911 Leganes, Spain., Elsharkawy MRM; Physics Department, Faculty of Science, Minia University, Minia P.O. Box 61519, Egypt. |
| Abstrakt: |
Free volume plays a key role on transport in proton exchange membranes (PEMs), including ionic conduction, species permeation, and diffusion. Positron annihilation lifetime spectroscopy and electrochemical impedance spectroscopy are used to characterize the pore size distribution and ionic conductivity of synthesized PEMs from polysulfone/polyphenylsulfone multiblock copolymers with different degrees of sulfonation (SPES). The experimental data are combined with a bundle-of-tubes model at the cluster-network scale to examine water uptake and proton conduction. The results show that the free pore size changes little with temperature in agreement with the good thermo-mechanical properties of SPES. However, the free volume is significantly lower than that of Nafion ® , leading to lower ionic conductivity. This is explained by the reduction of the bulk space available for proton transfer where the activation free energy is lower, as well as an increase in the tortuosity of the ionic network. |
