Correlation between proton conductivity, thermal stability and structural symmetries in novel HPW-meso-silica nanocomposite membranes and their performance in direct methanol fuel cells
Shen, Pei Kong
De Marco, Roland
Jiang, San Ping
Date of Issue2012
School of Mechanical and Aerospace Engineering
The intrinsic relationship between proton conductivity, thermal stability and structural symmetries of phosphotungstic acid (HPW)-functionalized mesoporous silica (HPW-meso-silica) membrane was investigated with mesoporous silica from 2D hexagonal p6mm, 3D face-centered cubic (View the MathML source), body-centered View the MathML source, to cubic bicontinuous View the MathML source symmetries. HPW-meso-silica nanocomposites with 3D mesostructures display a significantly higher proton conductivity and higher stability as a function of relative humidity in comparison to 2D mesostructures. The best result was obtained with body-centered cubic (View the MathML source)-HPW-meso-silica, showing proton conductivities of 0.061 S cm−1 at 25 °C and 0.14 S cm−1 at 150 °C, respectively, and an activation energy of 10.0 kJ mol−1. At 150 °C, the cell employing a HPW-meso-silica membrane produced a maximum power output of 237 mW cm−2 in a methanol fuel without external humidification. The high proton conductivity and excellent performance of the new methanol fuel cells demonstrate the promise of HPW-meso-silica nanocomposites with 3D mesostructures as a new class of inorganic proton exchange membranes for use in direct methanol fuel cells (DMFCs).
Journal of membrane science