多孔矽應用於微型直接甲醇燃料電池之擴散層暨觸媒載體之研製

Abstract

隨著科技的進步與環保意識的高漲，人類亟需一種乾淨、無汙染的能量來源，以應用於現今生活中不可或缺的可攜式電子產品。 直接甲醇燃料電池(DMFC, direct methanol fuel cell)被視為最有潛力，將取代目前鋰電池之下一代能源裝置。它具有操作溫度低，啟動速度快，能量密度高，燃料攜帶方便，燃料取得容易等優點。因此，本研究希望將燃料電池微型化，嘗試製造DMFC (micro DMFC)，並簡化其組成元件，降低製造成本，以實現整合於可攜式電子產品中的可能性。 本研究分為四大實驗項目：(1) 利用TMAH溶液與添加劑所調配之蝕刻液，進行具凸角保護特色的流道製備；(2) 製造與流道相銜接的多孔矽層，取代碳紙於DMFC中擴散層角色；(3) 比較多孔矽擴散層厚度對DMFC性能之影響；(4) 比較DMFC分別以多孔矽與碳紙做為擴散層之性能差異。 實驗結果顯示，本實驗以廉價的TMAH濕蝕刻技術，添加特殊界面活性劑，成功製造出具凸角蝕刻抑制的375 m深流道結構；此外，厚度高達300 m，且互相聯通的多孔矽擴散層，已藉由光輔助電化學蝕刻 (PAECE, photo-assist electrochemical etching ) 製程實現，並成功的與流道相銜接，達到簡化DMFC結構的目的。 實驗結果顯示，具多孔矽擴散層深度為225 m 的微型甲醇燃料電池，其最大開路電壓為387mV；最大電流密度為1.828 mA/cm2；最大功率密度為0.142 mW/cm2，與具碳紙擴散層的對照組性能(0.150mW/cm2)表現不相上下。多孔矽取代碳紙於微型燃料電池之擴散層應用將指日可待。 關鍵字：燃料電池，甲醇，多孔矽，擴散層。With the state of the art and the raised environmental consciousness, humans need certain power sources which are clean and environmentally friendly applied on daily-used portable electronic devices. DMFCs (DMFC, direct methanol fuel cell) were thought as the most promising power suppliers to replace lithium battery in next generation and are characterized with low operation temperature, rapid activation, high energy density, ease of carry and acquirement. Therefore, this research tried to fabricate a DMFC(micro DMFC), simplified its constitution and lower the cost to realize the possibility of DMFC integrated with portable electronic devices. This research were divided into four items: (1) flow channels realization with convex corner protected were fabricated with etchant composed of TMAH and additive; (2) porous silicon layer connected with flow channel were considered to replace carbon paper as diffusion layer; (3) the comparison of different thickness of porous layer with performances of DMFCs; (4) comparisons of performances resulted from porous silicon and carbon paper as diffusion layers. Experiments show that the 375 m-deep channel were successfully realized using TMAH solution with specific surfactant added; furthermore, the interconnected, 300 m-deep porous silicon diffusion layer connected with flow channels was achieved by PAECE (photo-assist electrochemical etching) process and the constitution of the DMFC were simplified also. The designed DMFC with 225 m-thick PS. Layer showed the maximum OCP of 387m V; maximum current density of 1.828 mA/cm2; maximum power density of 0.142 mW/cm2 and nearly equal to the performance (0.150 mW/cm2) of DMFC with carbon diffusion layer. Experimental result showed that using PS. layer in replace of carbon paper would be the promising way in DMFC application. Keywords: fuel cell, methanol, porous silicon, diffusion layer