摘要
近年來，質子交換膜燃料電池（PEMFC）的研究已經吸引越來越多的注意，質子交換膜燃料電池不僅擁有相當高的使用效率，且因其反應產物只有液態水，與傳統燃燒化石燃料會產生溫室氣體相比，是較為環保且可再生的能源。目前商用催化層材料是以碳黑搭載白金觸媒。但碳黑在PEMFC的操作條件下會腐蝕且產生一氧化碳，使得白金顆粒掉落以及對白金產生毒化效應，不僅使白金使用效率降低，更使電池的效能隨操作時間而降低。
本論文係選用氮化鋯(ZrN)及氮化鈮(NbN)取代碳黑作為載體，以利用這兩種過渡金屬氮化物良好的導電性及抗腐蝕性來提升電池的效能。氮化鋯及氮化鈮分別由溶膠凝膠法製備的氧化鋯(ZrO2)及商用氧化鈮(Nb2O5)，透過高溫氮化合成。氮化鋯及氮化鈮經分析顯示，皆為無微孔的結構，且比表面積都相當低。白金奈米顆粒是由化學還原法合成於載體上，以四氯化鉑為前驅物及硼氫化納為還原劑，分別製備重量百分比20, 10, 5 wt%的白金於ZrN及NbN上。由SEM觀察，ZrN (Pt@ZrN)及NbN (Pt@NbN)上的白金顆粒大小分別為3-6 nm及4-10 nm，顆粒的分布非常均勻且密集。
白金在ZrN及NbN上的電化學活性由循環伏安法(cyclic voltammetry, CV)及氧還原反應(oxygen reduction reaction, ORR)來鑑定，並與商用材的Etek (Pt@C, 20 wt% Pt)來比較，在三種試片中，Etek的電化學表面積(electrochemical surface area, ECSA)及質量活性(mass activity, MA)皆為最高，而Pt@ZrN的此兩數值皆為最低，由SEM發現，經過超音波震盪之後，ZrN上的白金會掉落，導致量測的ECSA值及MA值降低。
電池的效率測試是以Pt@ZrN或Pt@NbN為催化層材料製作電極，並與商用電極Etek (Pt@XC-72, 0.5 mg /cm2 Pt)電極組成全電池(Pt@ZrN/Etek, Pt@NbN/Etek)，以單電池測試平台測試其效能，並與以商用電極製成的全電池(Etek/Etek)進行比較。Pt@ZrN電極在陽極或陰極端的效率都非常低，白金密度0.5 mg /cm2的電極，在陽極與陰極端的最大功率密度分別只有193 及 11 mW/cm2。此外，陽極端的效率會隨測試循環數的增加而遞減。而在Pt@NbN電極方面，白金密度0.5 mg/cm2的電極在陽極端的表現與Etek相近，最大功率密度可到376 mW/cm2，但隨著白金密度的下降，電池的表現也隨之大幅降低。而Pt@NbN電極作為陰極端的效率則非常的差，白金密度0.5 mg/cm2的電極最大功率密度僅有38 mW/cm2。
為提高催化層的質傳能力，將碳黑(Vulcan® XC-72)與Pt@ZrN或Pt@NbN粉末以40 wt%的比例混合(40 wt% XC-72, 60 wt% Pt@ZrN或Pt@NbN)，並製備成電極，以Pt@ZrN-C及Pt@NbN-C製備的電極，在電池的表現上都有顯著的成長。Pt@ZrN-C電極在陽極端的效率隨測試循環數上升而下降的現象消失，且白金密度0.5 mg/cm2的電極最大功率密度可達444 mW/cm2，高於Etek電極的表現(420 mW/cm2) 。陰極端的表現上也有顯著的提升，最大功率密度可達348 mW/cm2。而以Pt@NbN-C電極作為陽極，白金密度0.5 mg/cm2的電極其最大功率密度可達406 mW/cm2，在陰極方面，最大功率密度為266 mW/cm2。

Abstract
In recent decades, there has been an increasing interest in the study of proton exchange membrane fuel cell (PEMFC) because it is a clean and efficient energy. Platinum and carbon black are the most common materials as catalyst and catalyst support, respectively. However, carbon might suffer corrosion problem under the operation environment of PEMFC, leading to the degradation of performance as time goes by.
In this study, zirconium nitride (ZrN) and niobium nitride (NbN) were chosen as candidates for catalyst support because of their good electrical conductivity and corrosion resistance. ZrN and NbN were successfully fabricated by thermal nitridation. Platinum was deposited on ZrN or NbN with 20, 10, and 5 wt% by wet chemical method with NaBH4 as a reducing agent. The dispersions of Pt nanoparticles on ZrN and NbN were very high and uniform. The particle sizes of Pt on ZrN and NbN were 3-6 and 4-10 nm, respectively. The values of electrochemical surface area (ECSA) and mass activity (MA) of Pt@ZrN, Pt@NbN, and Etek were determined by cyclic voltammetry (CV) and oxygen reduction reaction (ORR), respectively. Etek showed the highest values of ECSA and MA, while Pt@ZrN showed the lowest. It was observed that Pt nanoparticles were detached from the surface of ZrN during the preparation of ink, which made it poor electrochemical characteristics.
The performances of MEA were evaluated by testing the cell which was prepared by Pt@ZrN or Pt@NbN electrode and Etek electrode (Pt@ZrN/Etek, Pt@NbN/Etek). The cell prepared by both Etek electrodes (Pt@XC-72, 0.5 mg/cm2 Pt) was tested as a standard. The maximum power densities by using Pt@ZrN electrode as the anode or cathode with 0.5 mg/cm2 Pt loading were 193 and 11 mW/cm2, respectively. The maximum power densities by using Pt@NbN electrode as the anode and cathode were 376 and 38 mW/cm2, respectively. After mixing with 40 wt% carbon black (Vulcan® XC-72), the maximum value of power density increased to 444 mW/cm2 by using Pt@ZrN-C electrode as the anode, which was better than that of Etek electrode (420 mW/cm2). On the cathode, the maximum power density was 348 mW/cm2. The maximum values of power density by using Pt@NbN-C electrode as the anode or the cathode increased to 406 and 266 mW/cm2, respectively.

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