奈米碳載體與銀系、錳系、鈷系觸媒於鹼性燃料電池陰極之研究

Abstract

在燃料電池之氣體擴散電極中，碳載體的選擇與觸媒種類的採用為相當重要的一環。在本研究中，我們以三種不同的碳材體（比表面積333 m2/g奈米碳球CNC、比表面積254 m2/g的Vulcan XC72與比表面積1500 m2/g的Black Pearl 2000做為氣體擴散電極，並且也利用承載同樣的觸媒後，探究其於氧氣還原反應中的催化活性。實驗結果顯示CNC在三者中為最佳的觸媒載體。 而後利用含浸法在奈米碳球上承載銀粒子、氧化錳、以及氧化鈷等催化劑，在極化曲線中均比無添加催化劑的CNC有更好的表現，三者之中銀粒子的添加表現最佳。由掃瞄式電子顯微鏡圖像與X-ray繞射圖顯示在奈米碳球中的銀粒子呈現直徑150-280 nm之球形且為良好的FCC晶型結構。 另外我們進一步利用化學還原法還原銀粒子。穿透式電子顯微鏡照片顯示我們在無使用保護劑下，將銀粒子直徑成功縮小至5-15 nm。並進一步顯示更好極化曲線中的表現（每單位公分1毫克的添加量，在電流密度200 mA/cm2下，電壓輸出0.95 V）。

The types of carbonaceous materials and electrocatalysts are crucial for gas diffusion electrode (GDE). In this study, GDEs made of catalyzed and non-catalyzed carbonaceous materials were investigated for their electrocatalytic performances in oxygen reduction reaction (ORR). Carbon nanocapsules (CNCs, 333 m2/g), Vulcan XC72 (254 m2/g), and Black Pearl 2000 (1500 m2/g) were chosen to fabricate GDEs. The results showed that CNC were an excellent catalyst support among these three candidates. Moreover, CNCs impregnated with Ag, MnOx, CoOx also demonstrated significant improvements in i-V curves over non-catalyzed CNCs. Among them, the Ag-CNC exhibited the highest performance. The SEM images and X-ray diffraction pattern demonstrated that Ag embedded in CNCs was in spherical shape with 150-280 nm in diameter showing well-crystallized FCC structure. In addition, the wet-chemical method was used to reduce Ag+ on CNCs. TEM images revealed that the particle size of Ag were successfully reduced to 5-15 nm without any protecting agent. Furthermore, the i-V curve showed that nano Ag-CNCs GDE exhibited superb electrocatalytic performance, delivering 0.95 V at 200 mA/cm2 with catalyst loading of 1 mg/cm2.