Texture and Surface Acidity Dependent Proton Conductivities of Porous Sulfated Zirconia

• Main Authors: Gu, Jhih-Ping, 古芝萍
• Other Authors: Chang, Sue-Min
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/67675824726031907769

碩士 === 國立交通大學 === 環境工程系所 === 100 === In this study, porous sulfated ZrO2 (S-ZrO2) powders were prepared as a promising alternative proton-conducting material for fuel cells. The porous structure, surface acidity and proton conductivity were examined and their relationships were investigated. The S-ZO2 samples were prepared through templating precipitation and hydrothermal method. The mesoporous S-ZrO2 samples exhibited the proton conductivities of 1.2-2.0×10-2 S/cm, and the conductivities were highly dependent on their specific surface areas (78-128 m2/g). The microporous S-ZrO2 sample templated with octyltrimethylammonium bromide (C8TAB) had a higher proton conductivity of 2.6 ×10-2 S/cm. Small pore sizes assist protons hopping between bulk water and surface acidic sites to promote conductive efficiency. Post impregnation of the mesoporous S-ZrO2 sample (C16TAB/Zr= 0.5, average pore size= 2.8, surface area= 128 m2/g) with a 0.9 M H2SO4 solution remarkably improved its proton conductivity from 2.0 ×10-2 to 9.5 ×10-2 S/cm. This value is twice higher than that of the commercial Nafion (5.2×10-2 S/cm). Both the pore size and surface acidity determine the water content and control the proton conductivity. Even though the microporous S-ZrO2 samples showed the highest capability for keeping water molecules, their proton conductivity were not higher than the post sulfation powders. Microporous channels with the pore size smaller than 0.6 nm block water tightly and retard proton diffusion. Therefore, the optimal pore size (0.6-2.8nm) and surface acidity can contribute to high proton conductivity.