铁—氮—碳薄膜的制备及作为氧气还原电催化剂的研究

发布时间：2018-05-04 15:19

  本文选题：铁-氮-碳薄膜 + 燃料电池　； 参考：《吉林大学》2015年硕士论文

【摘要】：燃料电池是一种理想的能源技术，具有能量转换效率高、环境污染物排放少、启动速率响应快等优点。但是燃料电池目前还没有实现广泛的商业化，限制其应用的最主要因素是造价昂贵。近年来，碱性燃料电池由于具有较高的能量转换效率、温和的工作环境和较低的工作温度，吸引了科学研究者的目光。然而，碱性燃料电池阴极氧的还原反应是一个较为缓慢的反应，所以需要催化剂来加速其反应的速率，铂基催化剂一直被认为是氧还原催化活性最佳的催化剂，但是铂为贵金属，不仅价格较高，而且产量有限。所以，寻找和发展一种价格较低并且催化活性较高的非铂基催化剂来代替铂基催化剂，被认为是降低燃料电池成本，实现其商业化推广进程的最佳途径。在众多的非铂基催化剂中，铁-氮-碳基催化剂具有较高的催化活性，较好的稳定性和较佳的甲醇耐受性，获得了科学研究者的广泛关注。 本文采用两种方法（磁控溅射-真空退火、磁控溅射-浸渍-真空退火）制备了铁-氮-碳薄膜氧还原催化剂，并研究了铁含量和退火温度对铁-氮-碳薄膜催化剂的结构、形貌和催化活性的影响。利用X射线衍射仪、扫描电子显微镜对铁-氮-碳薄膜催化剂进行物相表征，利用X射线光电子能谱对铁-氮-碳薄膜催化剂中氮的化学键态进行表征，利用电化学工作站对铁-氮-碳薄膜催化剂的氧还原催化活性、稳定性和甲醇耐受性进行表征。 采用磁控溅射-真空退火法制备了铁-氮-碳薄膜催化剂。研究结果表明，随着铁含量的增加，铁-氮-碳薄膜催化剂对氧还原的催化活性逐渐降低。通过调节退火温度（600-900℃），实现了对氮的化学键态的有效控制，优化了氧还原催化活性，确定了氧还原催化活性位为吡啶氮。发现具有1.4at.%铁含量，经700℃退火的铁-氮-碳薄膜催化剂表现出最高的催化活性，其开启电压为0.04V，极限电流密度为4.12mAcm2，动力学电流密度为15.56mAcm2，电子转移数为3.42。 采用磁控溅射-浸渍-真空退火法制备了含有微量铁的铁-氮-碳薄膜催化剂。通过调节铁含量和退火温度，优化了铁-氮-碳薄膜催化剂的催化活性，探讨了氧还原催化活性位。研究结果表明，具有0.3at.%铁含量，经800℃退火的铁-氮-碳薄膜催化剂表现出最高的催化活性，其开启电压为0.07V，极限电流密度为4.51mA cm2，动力学电流密度为18.56mAcm2，电子转移数为3.86，近似催化4电子转移的氧还原反应过程。较高的催化活性归因于微量的铁和吡啶氮发生了键合，形成了高活性的FeN4催化活性位。 此外，采用这两种方法制备的铁-氮-碳薄膜催化剂在碱性溶液中的稳定性和甲醇耐受性均优于商业的Pt/C催化剂，，可以作为一种性价比较高的非铂基催化剂。
[Abstract]:Fuel cell is an ideal energy technology, which has the advantages of high energy conversion efficiency, low emission of environmental pollutants and fast start-up rate. However, fuel cells are not yet widely commercialized, and the most important factor limiting their application is the high cost. In recent years, alkaline fuel cells have attracted the attention of scientific researchers because of their high energy conversion efficiency, mild working environment and low working temperature. However, the cathodic oxygen reduction reaction of alkaline fuel cell is a slow reaction, so the catalyst is needed to accelerate the reaction rate. Platinum based catalyst has been considered as the best catalyst for oxygen reduction catalytic activity. But platinum is precious metal, not only high price, but also limited production. Therefore, it is considered to be the best way to reduce the cost of fuel cells and to realize the commercialization process of fuel cells by finding and developing a kind of non-platinum based catalysts with lower price and higher catalytic activity to replace platinum-based catalysts. Among the many non-platinum-based catalysts, iron-nitrogen-carbon-based catalysts have higher catalytic activity, better stability and better methanol tolerance, which have attracted wide attention of scientific researchers. In this paper, two methods (magnetron sputtering-vacuum annealing, magnetron sputtering-impregnation-vacuum annealing) have been used to prepare the oxygen reduction catalyst for iron nitrogen carbon thin film. The structure of iron nitrogen carbon film catalyst with Fe content and annealing temperature has been studied. Effects of morphology and catalytic activity. The phase of Fe-N-C thin film catalyst was characterized by X-ray diffractometer and scanning electron microscope (SEM). The chemical bond state of nitrogen in Fe-N-C thin film catalyst was characterized by X-ray photoelectron spectroscopy (XPS). The catalytic activity, stability and methanol tolerance of iron-nitrogen-carbon thin film catalysts were characterized by electrochemical workstation. Fe-N-C thin film catalysts were prepared by magnetron sputtering-vacuum annealing. The results show that with the increase of iron content, the catalytic activity of iron-nitrogen-carbon thin film catalyst for oxygen reduction decreases gradually. By adjusting the annealing temperature of 600-900 鈩

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