聚对苯二胺和炭黑复合物作为高效的氧还原催化剂及其稳定性研究（英文）

发布时间：2018-04-28 04:17

本文选题：苯二胺 + 炭黑　；参考：《催化学报》2016年07期

【摘要】：近年来,氮掺杂的碳材料作为碱性氧还原催化剂得到了研究者的广泛关注.掺杂的N原子会影响C原子的自旋密度和电荷分布,导致碳材料表面产生"活性位点",因此掺氮碳材料具有优秀的氧还原活性,这已经在理论计算和实验中得到了验证.我们通过调节聚对苯二胺和碳黑的比例,之后进行热解制备了一系列掺氮碳材料.其中0.88PpPD/CB样品具有最好的氧还原活性,其在KOH溶液(0.1 mol/L)中的氧还原性能超过了商业碳载铂.通过扫描电子显微镜表征,发现碳球聚集在聚对苯二胺的表面,这主要是因为聚对苯二胺没有进行酸掺杂,因此其水溶性比较差.通过氮气的吸脱附表征,发现聚对苯二胺的比表面积很小,而碳黑样品(BP2000)的比表面积很大.因此,随着聚对苯二胺量的增加,聚对苯二胺/碳黑复合物的比表面积逐渐降低.另外,聚对苯二胺表面几乎都是微孔,而介孔和大孔主要来自于碳黑.研究者认为,"活性位点"主要位于微孔内(聚对苯二胺表面),而介孔和大孔有利于物质的传输.因此,当聚对苯二胺和碳黑的比例合适时,既有大量的"活性位点"暴露,又有足够的介孔和大孔进行物质传输,所以0.88PpPD/CB样品的氧还原活性最高.但是,对于掺氮碳材料来说,一个主要的问题就是稳定性不足.不管是电化学稳定性,还是放置在空气中的稳定性,掺氮碳材料都比不上铂基催化剂,这也阻碍了它们的大规模应用.对于电化学稳定性,很多文章都进行了报道,但是很少有文章报道掺氮碳材料在空气中的稳定性.我们知道,铂基材料之所以具有优异的氧还原活性,是因为铂和氧气的结合能比较合适,既利于氧气吸附,也利于之后氧气分子键的断裂.但是,当铂基材料放置在空气中,氧气的吸附也会发生,而且之后会导致表面氧化层的形成.所以铂基材料需要活化才能达到最好的催化性能.对于掺氮碳材料,放置在空气中会不会发生氧化反应?这对氧还原活性是否有影响?为了研究掺氮碳材料在空气中的稳定性,我们将0.88PpPD/CB样品在空气中放置了一个月,之后再进行电化学测试.旋转圆盘电极测试表明,在空气中放置了一个月后,0.88PpPD/CB样品的氧还原活性降低了,不管是半波电位还是极限电流密度都下降了.之后我们对其进行了X射线光电子能谱检测,发现在空气中放置了一个月后其氧含量提高了1%(原子分数),而氮含量几乎没有变化.氧含量的提高证实了氧化反应的发生,但不能直接归结于空气中的氧气.为了排除其他因素,如水蒸气、二氧化碳等,当热处理完成,管式炉温度低于100°C时,我们将高纯氮气切换为高纯氧气,一个小时后再取出样品.电化学测试表明,在氧气中暴露了一个小时后,0.88PpPD/CB样品的氧还原活性极大地降低了,而且X射线光电子能谱表明其氧含量提高了一倍,接近12%.因此,我们证实了氧气会和0.88PpPD/CB样品反应,导致样品的氧还原活性降低.所以,对于未来掺氮碳材料的大规模应用,要考虑其在空气中的稳定性,以及如何避免和氧气接触.
[Abstract]:In recent years, nitrogen doped carbon materials have been widely concerned as basic oxygen reduction catalysts. Doping N atoms will affect the spin density and charge distribution of C atoms, resulting in the production of "active sites" on the surface of carbon materials. Therefore, nitrogen doped carbon materials have excellent oxygen reduction activity, which has been obtained in theoretical calculation and experiment. By adjusting the ratio of polyphenylene two and carbon black, we prepared a series of nitrogen doped carbon materials by pyrolysis, in which the 0.88PpPD/CB samples had the best oxygen reduction activity and the oxygen reduction performance in the KOH solution (0.1 mol/L) exceeded the commercial carbon loaded platinum. The surface of benzyl two amine is mainly due to the poor water solubility of polyphenylene two amine, so its water solubility is poor. It is found that the specific surface area of polyphenylene two amine is very small and the specific surface area of carbon black sample (BP2000) is very large. Therefore, the ratio of polyphenylene two amines increases with the increase of polyphenylene two amine / carbon black complex. The surface area is gradually reduced. In addition, the surface of polyphenylene two amine is almost all micropores, and mesoporous and large pores mainly come from carbon black. The researchers believe that the "active site" is mainly located in the micropores (polyphenylene two amines surface), while mesoporous and pore are beneficial to the transfer of material. Therefore, when the proportion of polyphenylene two amines and carbon black is suitable, there is a large amount of "live". 0.88PpPD/CB samples have the highest oxygen reduction activity. However, for nitrogen doped carbon materials, one of the main problems is the lack of stability. No matter the electrochemical stability or the stability in the air, the nitrogen doped carbon materials are not more than the platinum based catalysts. Many articles have been reported on electrochemical stability, but few articles report on the stability of nitrogen doped carbon materials in the air. We know that the excellent oxygen reduction activity of platinum based materials is because the combination of platinum and oxygen is more suitable and is beneficial to oxygen adsorption. It also helps to break the oxygen molecular bond. But when the platinum material is placed in the air, the adsorption of oxygen will also occur, and then the formation of the surface oxide layer. Therefore, the platinum base material needs activation to achieve the best catalytic performance. Is there an effect on the original activity? In order to study the stability of nitrogen doped carbon materials in the air, we put 0.88PpPD/CB samples in the air for one month and then carry out electrochemical tests. The rotating disk electrode test showed that after one month in the air, the oxygen reduction activity of 0.88PpPD/CB samples decreased, no matter the half wave potential. The limit current density decreased. Then we tested it by X ray photoelectron spectroscopy, and found that after a month in the air, the oxygen content increased by 1% (atomic fraction), and the nitrogen content was almost unchanged. In addition to other factors, such as water vapor, carbon dioxide, and so on, when the heat treatment is completed and the tube furnace temperature is below 100 C, we switch high pure nitrogen to high pure oxygen, and then take out the sample after one hour. The electrochemical test shows that after an hour of exposure to oxygen, the oxygen reduction activity of the 0.88PpPD/CB sample is greatly reduced, and the X ray light is greatly reduced. The electron spectrum showed that the oxygen content increased by one time. As close to 12%., we confirmed that oxygen would react with the 0.88PpPD/CB sample and reduce the oxygen reduction activity of the sample. Therefore, for the large-scale application of nitrogen doped carbon materials in the future, the stability in the air and how to avoid contact with oxygen should be considered.

【作者单位】：南京大学现代工程与应用科学学院;南京大学固体微结构物理国家重点实验室人工微结构科学与技术协同创新中心;南京大学昆山创新研究院;南京大学(苏州)高新技术研究院;
【基金】：supported by the National Natural Science Foundation of China(21476104) the Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province(BK20150009) the Natural Science Foundation for Young Scholars of Jiangsu Province(BK20150396) the Soft Science Research Program of Jiangsu Province(BR2015009) the Nanotechnology Program of Suzhou(ZXG2013029) the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,Qing Lan Project of Jiangsu Province the Fundamental Research Funds for the Central Universities,China~~
【分类号】：O643.36

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