氮摻雜二氧化鈦奈米管於燃料電池觸媒載體的應用; N-doped TiO2 Nanotube for PtRu Catalysts in Fuel Cells

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题名:	氮摻雜二氧化鈦奈米管於燃料電池觸媒載體的應用;N-doped TiO2 Nanotube for PtRu Catalysts in Fuel Cells
作者:	張傑鈞;Chieh-Chun Chang
贡献者:	化學研究所
关键词:	相變化;氮摻雜二氧化鈦奈米管;陽極觸媒;甲醇氧化活性;nitrogen-doped titanium dioxide nanotube;phase transfer;methanol oxidation activity;anodic catalyst
日期:	2010-07-26
上传时间:	2010-12-08 14:17:51 (UTC+8)
出版者:	國立中央大學
摘要:	本研究乃有關於改良直接甲醇燃料電池陽極觸媒系統。研究中使用氮取代技術將氮摻雜於二氧化鈦奈米管 (N-TiNT)，提昇導體電子導電度，改善觸媒金屬與載體間作用力，增進觸媒金屬對於甲醇的氧化能力，達到提昇燃料電池效能的目地。　　管狀二氧化鈦奈米管 (TiNT)具有高表面積以及低維傳導的特性。經由氮摻雜以氮元素取代氧化鈦奈米管中的氧元子，可以有效的提升載體的電子導電度。以四點探針評估導電度由10-7 Scm-1上升至10-1 Scm-1。經由高解析掃描穿透式電子顯微鏡 (HRSTEM) 發現N-TiNT表面有別於未鍛燒之TiNT並呈現許多的皺摺。經由EELS mapping了解氮原子均勻分布於管壁；粉末X光繞射儀則發現TiO2的Anatase相於高溫下逐漸轉成TiN的結晶相變化；光電子能譜儀顯示主要鍵結能為396eV和400eV，並確定氮取代最高可達27.55at%。　　在觸媒製作上，本研究選用通用的鉑釕金屬系統採用醇類還原法進行鉑釕合金的觸媒合成。研究顯示PtRu觸媒粒子，能夠在氮摻雜二氧化鈦奈米管載體上均勻分散達到鉑釕合金最佳化。氮摻雜二氧化鈦奈米管則具有幫助觸媒金屬抵抗一氧化碳使其較不易被毒化而失去活性的能力。使用循環伏安法 (Cyclic Voltammetry, CV) 發現氮摻雜催化甲醇電流密度最佳可達653 A/g Pt、抗CO毒化率 (CO Tolerance) If/Ib值最高可達5.69；此外該載體能與PtRu產生較強的作用力，穩定金屬而不易聚集，並且具有抵抗酸性物質腐蝕的能力，這些特性都將有利於增加甲醇氧化活性與電池的使用壽命。CO脫附 (CO Stripping) 測試化學活性面積 (Electrochemical Surface Area, ECSA) 達104 m2/g；定電壓安培法 (Chronoamperometry, CA) 測試觸媒長時間使用效能有所提升；最後再以單電池MEA進行極化與效能測試發現其效能較目前商用E-TEK來得優越。　　This research pertains to the development of novel anodic catalyst of direct methanol fuel cells. The use of nitrogen doped titanium nanotubes improves electronic conductivity and the interaction between metal and support, leading to the improvement of methanol oxidation efficiency and the performance of fuel cell. 　　Titania nanotube bears much higher surface area and favorable low dimension conducting property. Through replacing the oxygen atoms on the surface of the TiO2 nanotube by nitrogen, the N-dopped TiNT raised electronic conductivity from 10-7 Scm-1to 10-1 Scm-1. The N-doped TiO2 tube shows higher surface area compared to conventional carbon materials. Using HRTEM observes some wrinkling on the surface differ from un-annealing one. Additional, EELS mapping helps to realize the nitrogen atoms are dispersion well；XRD to realize the morphology and the phase transfer, the phase is transferred from Anatase to TiN follow by temperature increase； The XPS revealed nitrogen content of about 27.55 wt%, and the binding energy is 396eV and 400eV, which confirms the bonding of Ti-N and TiO-N. 　　Synthesize the PtRu alloy catalyst is achieved by alcohol reduction method. The study shows the majority of metal nano particle reside on the metal oxide tube surface and the Pt-Ru nanoparticles are well dispersed and indicate, that the metal oxide is effective in preventing the particle aggregation, giving rise to higher electrochemical active surface area. The N-TiNT/C/PtRu exhibited a mass current density of 653 A/g Pt, which is much higher than that of E-TEK (358 A/g Pt) measured under the same condition.；.The If/Ib ratio is higher to 5.69, which mean highly CO tolerance. In addition, present study shows that the nitrogen doped TiO2 as the support for metal nano-particle, nitrogen improve both the electrocatalytic oxidation activity and benefit CO-tolerance. CO-stripping measure the ECSA (Electrochemical Surface Area) can reach to 104 m2/g. The catalyst with N-TiNT support displayed a relatively lower CO to CO2 oxidation potential compare to E-TEK, which implies better CO oxidation capability compared to commercial E-TEK catalysts and the MEA performance is substantially improved.
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