【作者】 姜悦；

【导师】 张新胜；

【作者基本信息】 华东理工大学 ， 化学工程， 2012， 硕士

【摘要】 纳米碳纤维由于其独特的电子及结构特性,近年来在作为催化剂和催化剂载体方面受到了广泛关注。氧还原反应几乎是所有燃料电池的阴极反应,且该反应广泛应用于金属腐蚀、能量转换与存储等领域,因此具有十分重要的研究意义。本论文的研究目的在于以纳米碳纤维作为催化剂或者催化剂载体,以氧还原反应为探针反应,研究纳米碳纤维的微结构及表面性质对氧还原催化活性的影响。目前得到的主要研究结果如下：(1)采用超声处理的方法分别在管式和鱼骨式纳米碳纤维表面成功引入含氧和含氮官能团。电化学测试结果表明,在0.1 M KOH溶液中,两种不同微结构的CNF的氧还原催化活性都遵循相同的趋势,即CNF-P<CNF-O<CNF-ON,且鱼骨式CNF的催化活性好于相应的管式CNF。说明纳米碳纤维的表面性质和微结构都会影响其在碱性溶液中的氧还原催化活性,而前者的影响可能更大些。(2)分别以含氧和含氮的f-CNF为载体,利用乙二醇法负载Pt纳米粒子,制备催化剂电极。电化学测试结果表明Pt/CNF-ON/GC电极的氧还原催化剂活性好于Pt/CNF-O/GC电极。一般认为,Pt/CNF-ON/GC电极较好的催化活性主要是由于Pt纳米粒子较小的颗粒尺寸、较均匀的颗粒分布、Pt与CNF-ON载体之间的协同效应及增强的结合力以及CNF-ON独特的结构和电子特性。(3)利用乙二醇法制备了不同Pt-Pd合金配比的催化剂,RDE结果表明,制备的合金催化剂随着铂含量的增加,氧还原催化活性依次增强,但含Pt量较多的Pt3Pd1/CNF例外。当Pt：Pd=2：1时,催化剂具有较好的氧还原催化性能,可归因于合适的Pt-Pd原子比、有利的原子间距和合金化程度的改变。更多还原

【Abstract】 Carbon nanofibers (CNFs) have attracted considerable attention as catalyst and catalyst support for ORR in recent years because of their special electrical and structural properties. The oxygen reduction reaction (ORR) at the cathode of fuel cells plays a key role in controlling the performance of a fuel cell, and efficient ORR electrocatalysts are essential for practical applications of the fuel cells.The purpose of this paper is to study the microstructure and surface properties of CNFs towards oxygen reduction reaction (ORR) using CNFs as catalysts or catalyst supports. The main results obtained up to now are as follows:(1) Oxygen- and nitrogen-containing functional groups were successfully introduced onto the t-CNF and f-CNF surface by sonochemical treatment in mixed acids (concentrated sulfuric acid and nitric acid) and ammonia, respectively. The ORR activity of the CNF catalyst was measured in an oxygen-saturated 0.1 M KOH electrolyte solution by rotating disk electrode technique. The RDE results show that the electrocatalytic activities of the two types of CNFs increase in the same sequence untreated CNFs< oxygen-containing CNFs< nitrogen-containing CNFs, while the f-CNFs-based catalysts have higher electrocatalytic activities for ORR than their t-CNFs-based counterparts. The above results indicate that the surface properties and the microstructures of CNFs both have effects on the electrocatalytic activity of CNFs for ORR, although the former may have a dominant effect.(2) The oxygen-and nitrogen-containing functional groups were introduced onto the f-CNF surface by sonochemical treatment in mixed acids (concentrated sulfuric acid and nitric acid) and ammonia, respectively. The Pt/CNF-ON/GC electrode exhibited a better electrocatalytic activity toward ORR compared with Pt/CNF-O/GC electrode. It is believed that the enhanced catalytic activity exhibited by the Pt/CNF-ON/GC electrode can mainly be attributed to the smaller Pt particle size and more uniform particle size distribution. The synergistic effect, the enhanced Pt-CNF-ON interaction, and the unique structural and electronic properties of CNF-ON may also contribute to the enhanced catalytic activity.(3) Pt-Pd alloy catalysts with different ratios of Pt and Pd were prepared by glycol method. RDE results show that the catalytic activity toward ORR of the alloy catalysts increased with the increasing platinum content, except for Pt3Pd1/CNF. Among these alloy catalysts, Pt2Pd1/CNF shows the highest ORR catalytic activity. The enhanced catalytic activity can be attributed to the appropriate Pt-Pd atomic ratio, a favorable degree of atomic spacing and the proper alloy extent.更多还原