以電化學方式於碳紙上成長金奈米結構及其在鹼性直接葡萄糖燃料電池之應用

Abstract

葡萄糖，在自然界中含量豐富、無毒、不可燃、便宜又容易使用與儲存。由於這些特性使得直接葡萄糖燃料電池成為具有前景的發電方式之一。當量測環境為鹼性時，不僅可以有效提高電池效能，也可使用較便宜的催化劑，如金、銀或鎳等金屬。而金在鹼性環境下對葡萄糖氧化有高度催化能力，且在自然界中非常穩定，因此我們選擇以金作為電池的觸媒。 在本篇論文中，我們利用簡單的電化學成長法在碳紙上製備出具有奈米結構的金，作為鹼性葡萄糖燃料電池觸媒。以金氯酸作為金的來源，並加入不同濃度的介面活性劑CTAC (cetyltrimethylammonium chloride) 和硝酸鈉，固定還原電位成長出金奈米珊瑚和奈米顆粒。 經實驗證實，金奈米珊瑚具有高表面積及對葡萄糖有高電催化能力。進一步，我們將製備的奈米結構金電極作為陽極與自製的鉑電極和陰離子交換膜組成膜電極組，並應用於鹼性葡萄糖燃料電池。結果顯示奈米顆粒與奈米珊瑚電極分別可得開路電壓為0.61 V以及0.64 V，而最高輸出功率為0.336 mW/cm2以及0.847 mW/cm2。另外，我們將電池進行放電測試，實驗顯示經過五個小時的放電，電壓降幅僅為6.9 %，且可經由電化學處理的方式，將我們的電極再生。因此，我們所製備出來的奈米珊瑚金電極不僅在電池上有相對較好的表現，且可經長時間的使用。最後，我們嘗試利用其他醣類作為電池燃料，以電化學方式探討，麥芽糖在金電極上具有較佳的電化學訊號。並以麥芽糖作為燃料，可得電池開路電壓為0.65 V，最大輸出功率0.834 mW/cm2。

Direct glucose fuel cells (DGFC) have attracted interest as one of the most promising power sources because glucose is abundant in nature, non-toxic, non-flammable, cheap and easy to store. It allows the use of inexpensive non-platinum metal catalysts such as gold, silver and nickel. Especially, Au is considered one of the promising non-Pt fuel cell catalysts as its good activity toward glucose oxidation in alkaline media. In this work, we demonstrated nanostructured Au material deposited on carbon papers can be used for direct alkaline glucose fuel cell. Au nanocorals and nanoparticles were grown on carbon papers via a simple two-electrode electrochemical deposition process by reducing HAuCl4 under constant potentials in mixtures containing cetyltrimethylammonium chloride (CTAC) and/or NaNO3. Electrochemical characterizations showed that the nanocoral electrode exhibited high surface area and high electrocatalytic activity towards glucose oxidation in alkaline media. These Au nanostructures were employed as the anodes and assembled with anion exchange membranes and Pt cathodes for alkaline direct glucose fuel cell (DGFC) investigations. Open-circuit voltages (OCV) of the Au nanocoral and nanoparticle electrodes were 0.64 V and 0.61 V, and their maximum power densities were 0.847 mW/cm2 and 0.336 mW/cm2, respectively. The cells showed stable output over 5 h with a small decrease in OCV (6.9 %). The electrodes could be refreshed after electrochemical reduction steps. Furthermore, we examined some monosaccharides and disaccharides as anodic fuel by cyclic voltammetry and maltose was selected as fuel for cell test. The polarization curve showed OCV of 0.65 V and the short-circuit current density of 5.70 mA/cm2.