以埃洛石为模板构筑贵金属@碳纳米反应器用于催化降解氯酚

Designing and fabrication of highly efficient catalysts is of great significance for catalytic degradation of chlorophenol environmental pollutions. In the present research, firstly, natural halloysite nanotube is selected as a template for adsorption and deposition of metal cations by electrostatic interaction, and then the absorbed metal cations are reduced to form noble metals/halloysite composites, which can enhance the dispersity of noble metals catalysts. Secondly, natural saccharides are absorbed onto noble metals/halloysite and underwent hydrothermal carbonization to form noble metals/halloysite nanotube@carbon nanocomposites. Then the noble metals@carbon nanoreactor is obtained by removal of halloysite template with chemical etching, in which noble metals are encapsulated and uniformly anchored in the carbon layer. Finally, catalytic hydrodechlorination of 2,4-dichlorophenol is used as a probe reaction to study the catalytic properties of the synthesized noble metals@carbon nanoreacor for degradation of chlorophenol environmental pollutions. With two natural materials as main raw materials, noble metals@carbon nanoreactor is fabricated in order to solve the general problems of leakage, aggregation and inactivation of noble metals nanocatalysts during catalysis and enhance their activity. The effect of structural factors on synergistic catalytic mechanism is also clarified. This research provides an efficient and economic nanoreactor for catalytic hydrodechlorination of chlorophenol environmental pollutions and for other catalytic processes as well.

高效催化剂的设计与制备对氯酚类环境污染物的催化降解具有重要意义。本研究首先以天然埃洛石纳米管为模板，利用其表面的静电作用吸附沉积金属阳离子，经还原得到贵金属/埃洛石纳米管复合材料，以此提高贵金属催化剂的分散性能；其次利用埃洛石纳米管表面对天然糖类的强吸附能力，在贵金属修饰的纳米管表面形成天然糖类包覆层，经水热碳化形成贵金属/埃洛石纳米管@碳复合材料；再利用化学刻蚀除去埃洛石纳米管模板，得到贵金属@碳纳米反应器，使贵金属纳米粒子均匀封装镶嵌在碳层内；最终以2,4-二氯酚催化加氢脱氯为例，研究贵金属@碳纳米反应器对氯酚类环境污染物的催化降解性能。本课题以两种天然材料为主要原料构筑贵金属@碳纳米反应器，以期解决催化过程中贵金属纳米催化剂流失、团聚和失活等共性问题，并提高其活性，阐明各结构因素对催化的协同机制，为氯酚类环境污染物的加氢脱氯降解及其它催化过程提供一种高效、经济的纳米反应器。

设计与制备高效的催化剂对催化过程具有重要意义。本项目以埃洛石纳米管和碳材料为载体，利用其表面的静电作用将贵金属活性组分组装到埃洛石纳米管和碳材料上，获得贵金属粒子高度分散、尺寸可控的贵金属/埃洛石纳米管和贵金属@碳复合材料，提高贵金属催化剂的分散性能，解决催化过程中贵金属纳米催化剂流失、团聚和失活等共性问题，并提高其活性。具体研究工作如下：（1）采用强静电吸附法和传统浸渍法分别制备了SEA-Pt/HNTs和IMP-Pt/HNTs纳米复合物。结果表明，强静电吸附法制备的SEA-Pt/HNTs催化的AB水解制氢反应的氢气选择性达到100%，其TOF值是传统浸渍法制备的IMP-Pt/HNTs的3倍。（2）采用强静电吸附法合成Pd纳米颗粒负载于HNTs上，再利用蒸发溶剂法将AB封装在Pd/HNTs内。结果表明，该复合材料具有优异的脱氢性能，可在较低的温度（60ºC）下释放氢气，并且完全抑制了体积膨胀现象和挥发性副产物（氨气、乙硼烷和硼嗪）的释放。（3）为了研究碳材料对金属纳米粒子的封装限域作用，我们以具有大比表面积的氮掺杂多孔碳（N-MCSs）作为载体，利用强静电吸附法制备了PtxCo1-x/N-MCSs纳米复合物，结果表明，Pt0.33Co0.67/N-MCSs纳米催化剂的催化活性最高，TOF值为单金属Pt/N-MCSs的13倍。该项目为贵金属/埃洛石纳米管和贵金属@碳纳米反应器在催化领域的实际应用提供理论依据。