Approach to High Performance Electrode Catalysts for DMFC

分别以介孔氧化硅材料MCM-48和SBA-15为模板剂合成了介孔炭。典型地，用蔗糖作为碳源和硫酸作为酸催化剂浸渍模板。碳源经脱水冷凝后，在900℃氩气气氛下进行碳化。通过用氢氟酸处理二氧化硅-碳复合物来从二氧化硅-碳复合物中除去二氧化硅，产生中晶碳CMK-1、CMK-3和CMK-5。另一种类型的碳也是用石油沥青合成的。MCF碳可以通过使用MCF二氧化硅作为模板来合成。通过蔗糖的两步浸渍和碳化制备了由具有直径约4 nm的中孔的封闭壁的球形中空体组成的碳结构。介孔结构在1400℃仍保持不变。铂负载在这些中孔碳上。TEM观察表明，在1100℃处理的介孔材料中存在小于2 nm的金属颗粒。金属分散不仅高度依赖于碳结构，而且还依赖于在惰性气体气氛中进行热处理的温度。后者被解释在表面官能团和它们的密度，这可能会影响表面和Pt源的相互作用的变化。载铂电极的氧还原活性高于乙炔衍生碳。Pt催化剂的性能不仅受Pt分散度的影响，而且受它们在碳电极中的分布的影响。

The mesoporous carbons were synthesized by using mesoporous silica materials such as MCM-48 and SBA-15 as a template, respectively. Typically, the templates were impregnated with sucrose as a carbon source and sulfuric acid as an acid catalyst. Following dehydration-condensation of the carbon source, the carbonization was carried out mainly at 900℃ under flowing argon. The silica was removed from the silica-carbon composite by treating it with hydrofluoric acid, producing mesoprpus carbons CMK-1, CMK-3, and CMK-5. Another type of carbon has been also synthesized by using petroleum pitch. MCF carbons can be synthesized by using MCF silica as a template. A carbon structure composed of spherical hollows with closed walls with mesopores of around 4 nm in diameter is prepared by the two-step impregnation of sucrose followed by carbonization. The mesoporous structure was maintained up to 1400℃. Platinum is loaded on these mesoporous carbons. TEM observations revealed the presence of metal particles of below 2 nm in the mesoporous material treated at 1100℃. The metal dispersion is highly dependent not only on the carbon structures but also on the temperature for thermal treatments in inert gas atmosphere. The latter is interpreted in terms of the change in the surface functional groups and their density, which probably affect the interaction of the surface and Pt sources. Oxygen reduction activity of the Pt-loaded electrode on CMK-1 was higher than that of the acetylene derived carbon. The performance of Pt catalyst was affected not only by the Pt dispersion but also by their distribution in the carbon electrode.