A study on gas diffusion electrode using high-temperature organic/inorganic hybrid material as electrolytic binder

• Main Authors: Gi-Hao You, 尤麒豪
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/99979990747651714867

碩士 === 國立雲林科技大學 === 化學工程與材料工程研究所 === 95 === A series of high-temperature hybrid materials using Bis (tri-ethoxysilyl) alkane (TES-alkane) and 3-(trihydroxysilyl) -1-propane sulfonic acid((THS)pro-SO3H) as precursors had been synthesized through a method of sol-gel reaction. (THS)Pro-SO3H has a sulfonic acid group on one end to conduct proton and silanol groups on the other end to conduct a condensation reaction. Form Si-O-Si inorganic phase cross-linked network structures. The effects of the (THS)Pro-SO3H content as well as the types of TES-alkane on the structures and properties of hybrid materials were investigated. The hybrid electrolyte was then studied in the aspects of proton conducting properties, such as ion-exchange capacity, water uptake, proton conductivity, and thermal property. Among TES-alkane series, bis (tri-ethoxysilyl) octane (TES-Oct) was selected as a major precursor, reacted with (THS)Pro-SO3H to form a sulfonic acid-functionalized organic-inorganic hybrid electrolyte material as gas diffusion electrode binder. The success of synthesis of hybrid materials was confirmed by FT-IR spectrum analyzer. The proton conductivity, water uptake and ion-exchange capacity increased with (THS)Pro-SO3H content. This indicated that has more sulfonic acid group in materials been able to promote protons to conduct and absorbed larger amount of water in the membrane. Dependence of addition of (THS)Pro-SO3H increased, sulfonic acid group number in the membrane increased. When the mole ratio of (THS)Pro-SO3H/TES-oct is at 1, the membranes exhibits the highest proton conductivity (2.15×10-2S/cm) and ion-exchange capacity (IEC) is 0.78 (mmol/g). And begin to present free water in the membrane. The proton conductivity of materials with various precursor could reach2~3×10-2S/cm, Among TES-alkane series hybrid materials, (THS)Pro-SO3H /TES-Eth with reasonable water uptake(173.1%) and ion-exchange capacity(1.32 mmol/g). SAXS and solid-state NMR were employed to investigate the morphology and structure of organic/inorganic hybrid materials respectively. The major interested factor include (i) types of TES-alkane, (ii) (THS)Pro-SO3H content. First, we used solid-state NMR to confirm the extent of sol-gel reaction. By the results, it was found that as hydrocarbon chain became longer, the extent of sol-gel reaction (degree of cross-linked) increased. Moreover, hexane as organic segment, the inorganic phase of organic/inorganic hybrid materials exhibits the highest extent of crosslink. And also reveal that have more residual Si-OH in the membrane makes the materials more hydrophilic. In contrast, when ethane as organic segment, the extent of cross-linked of inorganic phase of hybrid material is lower. The (THS)Pro-SO3H/ TES-alkane hybrid materials exhibit excellent thermal stability by TGA experiment. In addition, the degree of cross-linked of (THS)Pro-SO3H /TES-Hex was higher than other hybrid materials cause the inorganic phase structure more tightly. It seems (THS)Pro-SO3H/TES-Hex hybrid material have better thermal property and that of (THS)Pro-SO3H/TES-Eth materials is lower. Finally, we prepared the gas diffusion electrode based on (THS)Pro-SO3H /TES -oct hybrid materials. The pore size distribution and pore volume in the catalyst layer were evaluated quantitatively. Incorporation of hybrid materials into catalyst layers leads to decrease of secondary and primary pore volume. These results indicate that hybrid materials penetrate into both pores, and leads to improve the efficiency of catalyst utilizes. The optimum addition ratio of hybrid at (THS)Pro-SO3H to catalyst is 1. At optimum composition, supply of both protons and reactants to catalyst sites was relatively higher so that cell could reach higher performance.