多重技術整合之微機電式μDMFC開發與性能評估

直接甲醇燃料電池(Direct methanol fuel cell, DMFC)具備能於低溫下工作、能量密度高、啟動速度快、燃料易取得、易攜帶、安全與穩定與低污染等優點，因此在未來有希望能取代鋰電池成為新一代的行動能源裝置。本研究以微機電系統(Micro-electromechanical system, MEMS)技術製作微型直接甲醇燃料電池(DMFC) ，並簡化元件結構與降低生產成本，以因應未來將其應用於行動電子產品之微小化需求。本研究主要以矽晶片作為燃料電池之基材，並整合「TMAH濕蝕刻技術」、「光輔助電化學蝕刻技術」、「PtRu二元金屬化鍍技術」以及「甲醇改質技術」，製作微流道搭配多孔矽(Porous silicon, PS)，以及微流道搭配穿孔矽(Through silicon via, TSV) 擴散層結構之燃料電池電極板，並將其應用於微型直接甲醇燃料電池的製作。本研究成功將PtRu二元金屬均勻複合於石墨烯與奈米碳管表面(PtRu/G-CNT)，其Pt與Ru含量比分別為34.1 Wt.%與2.6 Wt.%，而在半電池表現，PtRu/G-CNT之氧化電流峰值為5 mA/cm2，是Pt/G-CNT以及PtRu/G的2.02倍與2.4倍。在電極組合部分，陽極與陰極分別使用多孔矽擴散層電極和穿孔矽擴散層電極的組合(PS+TSV)，能得到最佳的電池性能表現，其最大開路電壓為0.4 V，與PS+PS相比增加約1.5倍，而與TSV+TSV相比增加約6.7倍。在添加界面活性劑改質甲醇燃料的評估試驗中得知，界面活性劑MA適於作為甲醇之濕潤劑，並能從添加濃度控制對甲醇氧化能力與濕潤性之影響，同時也能增加二氧化碳氣泡脫離，避免覆蓋觸媒層造成毒化，進而提升燃料電池之性能表現。在添加界面活性劑MA量為0.1 %時，其最大功率密度為0.336 mW/cm2與最大開路電壓為0.48 V，相較於未添加界面活性劑MA分別提升了1.4倍與1.2倍，說明加入少量界面活性劑能促進甲醇藉由多孔矽擴散至觸媒層進行反應，但若加入過多界面活性劑將會影響甲醇氧化效率，因而造成電池性能的下降。

關鍵字

直接甲醇燃料電池；多孔矽；穿孔矽；二元金屬；界面活性劑

並列摘要

Direct methanol fuel cell (DMFC) has the advantages of being able to work at low temperature, high energy density, fast starting speed, easy fuel availability, easy portability, safety, stability, and low pollution. Therefore, DMFCs were thought as the next generation of power suppliers to replace lithium battery in the future. In this study, micro-electromechanical system (MEMS) technology was used to fabricate micro direct methanol fuel cells (DMFCs), simplifying component structure and reducing production costs in order to meet the needs of miniaturization of mobile electronic products in the future. In order to meet the miniaturization demand of portable electronic devices, this research tried to fabricate a μDMFC, simplify component, and lower cost by using MEMS technique. This research used TMAH etching, PEACE, PtRu chemical reduction, and methanol modification to fabricate the porous silicon diffusion layer (PS) electrode with channel structure and through silicon via (TSV) electrode with channel structure. This study successfully synthesis PtRu binary metal uniformly to the surface of graphene and carbon nanotubes. The PtRu content ratio is 34.1 wt.% and 2.6 wt.%, respectively. In the half-cell performance, the peak current of oxidation of PtRu/G-CNT is 5 mA/cm2, which is 2.02 times and 2.4 times that of Pt/G-CNT and PtRu/G. Experiments show that using the PS electrode in anode and the TSV electrode in cathode would get the maximum open circuit voltage (0.4 V), which is 1.5 times and 6.7 times that of PS+PS and TSV+TSV. In the evaluation test of adding surfactant-modified methanol fuel, it is known that surfactant MA is suitable as a wetting agent for methanol, and it can influence the oxidation ability and wettability of methanol by concentration controlling. and also increase carbon dioxide bubbles. At the same time, it can improve the performance of the fuel cell by increasing the detachment of carbon dioxide bubbles to avoiding the poison caused by covering catalyst layer. When the amount of MA added is 0.1%, the maximum power density is 0.336 mW/cm2 and ,the maximum open circuit voltage is 0.48 V, which is 1.4 times and 1.2 times than un-added respectively. It is indicated that the addition of a small amount of surfactant can promote the reaction of methanol to the catalyst layer by diffusion of porous. However, if too much surfactant is added, the oxidation efficiency of methanol will be affected, resulting in a decrease in battery performance.