機械合金法合成鎂基儲氫材料及氫化性質之研究

Hydrogenation properties of Mg-based hydrogen storage materials synthesized by mechanical alloying method

吳坤洲(Kwen-Chou Wu)

指導教授 ： 沈家傑

元智大學/工程學院/先進能源碩士學位學程/碩士(2012年)

https://doi.org/10.6838/YZU.2012.00321

摘要

本研究擬以球磨機械合金法製備高性能鎂鈦MgH2-xTiH2-tmh (x = 0、0.1、0.3、0.5 mole及tm = 4、10、25、62.5 h) 儲氫材料。未球磨MgH2在300 ℃及30分鐘內可吸3.2 wt %的氫氣，經球磨10 h的MgH2可在相同條件下吸6.8 wt %的氫氣。添加TiH2至MgH2隨著球磨時間增長，SEM-EDS元素映像圖顯示TiH2散佈在MgH2上的均勻性變佳。經XRD繞射鑑定，球磨後TiH2 (111)及MgH2 (101)兩個晶面有疊峰現象，判斷兩種原始材料已形成β-MgH2 + δ-TiH2 + FCC-MgH2之複合材料。添加TiH2修飾MgH2之後，TPD脫附曲線起始脫氫溫度從350 ℃降至200 ℃。 MgH2-0.1TiH2-25h僅在3分鐘內，於室溫25 ℃及300 ℃分別吸3.7 wt %及5.5 wt %的氫氣，吸氫速度非常快，推測原因為TiH2之氫空缺所產生H pump效應所致。同時，隨著球磨時間的增加，所形成的新型鎂鈦複合材料之PCI曲線的吸放氫壓力可有效抬升，由van’t Hoff plots分析得知，此新型的FCC-MgH2儲氫材料放氫生成焓及生成熵分別為-78.2±1.5 kJ/mol H2及-233±2 J/k mol H2。

關鍵字

儲氫材料 ； 球磨 ； PCI曲線 ； H pump

並列摘要

The aim of this study is to develop high performance Mg-Ti hydrogen storage materials by mechanical alloying method. As-received MgH2 without ball-milled can absorb hydrogen of 3.2 wt % within 30 minute at 300 ℃. After ball milling for 10 h, the MgH2-10h can absorb hydrogen of 6.8 wt % at the same condition. The dispersion of TiH2 on the MgH2 was good according to the result of the SEM-EDS area mapping. The superimposed of X-ray diffraction peaks of the TiH2 (111) and MgH2 (101) indicated that the two starting material have now become composite with β-MgH2 + δ-TiH2 + FCC-MgH2. Based on the TPD desorption curves, MgH2 doped with TiH2 started to release hydrogen gas at 200 ℃. The as-milled MgTi materials can absorb hydrogen of 3.7 and 5.5 wt %, respectively at room temperature 25 ℃ and 300 ℃ within 3 minutes. This significant enhanced hydrogen absorption rate was ascribed to the δ-TiH2-y-catalyst, in which H atoms can be pumped to Mg through the y vacancy lattice sites of TiH2-y. The PCI curves indicates that both hydrogen absorption and desorption pressures can be increased with reaction time of ball milling. According to van’t Hoff plots, the enthalpy and entropy of the FCC-MgH2 was estimated to be 78.2±1.5 kJ/mol H2 and -233.2±2 J/k mol H2,respectively.

並列關鍵字

hydrogen storage material ； ball milling ； PCI curve ； H pump

參考文獻

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