奈米碳材作為直接甲醇燃料電池陰極電極之研究

Abstract

本研究乃是利用具高表面積之奈米碳材作為直接甲醇燃料電池之陰極電極材料，藉以增加載體面積，以期能增加電池性能與減少觸媒使用量。首先以離子濺鍍法於碳布表面鍍上鐵的微粒子作為成長奈米碳管的觸媒，接著使用微波電漿化學沈積法，於碳布表面直接長多壁奈米碳管與奈米薄片，來作為直接甲醇燃料電池陰極鉑觸媒之載體。本實驗利用離子濺鍍以及聚醇法兩種不同的方法將鉑披覆於奈米碳管表面，分別以改變濺鍍時間與溶液濃度的方式來改變觸媒的載量。同時以SEM、TEM分別觀察觸媒吸附於碳管表面的形態，以及利用XRD與EDX來計算觸媒顆粒尺寸與重量百分比。最後使用循環伏安法於0.5M的硫酸溶液中量測氫吸附、脫附於鉑觸媒上的能力，來計算出鉑觸媒實際上能有效活化的面積，並量測鉑觸媒顆粒於0.5M硫酸與1M甲醇混合水溶液中氧化電流的大小，藉此來比較不同觸媒披覆製程對於觸媒活化能力的影響。實驗結果發現離子濺鍍法於多壁奈米碳管上所批覆的觸媒活性面積較聚醇法來得大，且在較低的觸媒用量時，能得到較大的電流。

High surface area carbon nanomaterials were used as cathode electrode for direct methanol fuel cell(DMFC).First, iron catalysts were deposited on carbon cloth for growing carbon nanomaterial by IBSD. Then MWCNT and nanoflake which are supports for DMFC cathode catalyst have been growth directly on the surface of carbon cloth by MPECVD method. Physical sputtering and Polyol methods were chosen for dispersing Pt catalysts on carbon nanomaterial. The amount of Pt particles are controlled by changing deposition time and solution concentration. SEM and TEM were used to observe the morphologies and structures of Pt particles adsorbed on carbon cloth. And we use XRD and EDX for calculating Pt particle size and weight percentage. Cyclic voltammetry (CV) in 0.5M H2SO4 solution shows the adsorption and desorption behavior of hydrogen ion on Pt particles ,which can be used to calculate the effective surface area of Pt particles. And CV is also used to measure the redox current in 0.5M H2SO4 and 1M CH3OH mixed solution. With the results, the influence of different catalyst deposition methods on the active ability of Pt catalyst can be obtained. Compared to chemical solution redox, Pt particles sputtered on CNT shows larger effective surface area and oxidation current .This also suggests that MWCNT on carbon cloth are suitable for the cathode catalyst support for DMFC.