过渡金属氮掺杂碳基材料的制备及其电催化氧还原性能的研究

发布时间：2018-02-23 21:36

本文关键词： 燃料电池氧还原反应过渡金属氮掺杂碳基催化剂　出处：《安徽大学》2017年硕士论文　论文类型：学位论文

【摘要】：燃料电池作为最具前景的能源转换技术之一,具有能量转化效率高、环境友好等优点,备受研究者的青睐。它是一种高效利用氢能的新能源,在电化学反应中能直接将化学能转换为电能的装置。因此阴极氧还原反应(Oxygen Reduction Reaction,ORR)在燃料电池中显得十分重要,其中,贵金属催化剂依然是当前性能最好的阴极ORR催化剂。然而,由于这些贵金属催化剂在自然界中储存量及其稀少、价格非常昂贵以及迟滞的动力学效应等,严重限制了燃料电池商业化应用。因此,开发和探索价格低廉、资源丰富、高效、耐用的非贵金属ORR催化剂显得十分重要,具有非凡的现实意义和应用前景。在目前研究的阴极ORR催化剂中,非贵金属碳基催化剂以其高效的催化活性和稳定性及高超抗甲醇毒性等特点,成为学术界广泛研究的课题。基于非贵金属碳基催化剂的研究现状及本课题组的工作基础,本论文选用碳纳米管、琼脂为主要的碳源,通过几种不同的方法将杂原子掺入过渡金属碳骨架中,成功制备了一系列高效的过渡金属碳基ORR催化剂。主要工作内容和成果包括以下几个方面:1.以碳纳米管、氨基磺酸钴、二腈二胺为原料,采用简单的超声分散、蒸发溶剂的方法制备前躯体复合物,并经过高温热解成功制备了氮、硫双掺杂钴/碳催化剂。通过扫描电镜、透射电镜、X射线衍射、BET比表面积测试等对最终产物进行表征,并分别在碱性和酸性溶液中测试最终产物的ORR性能。电化学测试结果表明,在碱性溶液中,典型催化剂表现出优异的ORR性能,极限扩散电流可达-5.43 mA cm-2,电子转移数接近4,抗甲醇毒性和长期稳定性也非常好。此外,典型催化剂在酸性条件下的电催化性能也比较好。这种介孔纳米管状氮、硫双掺杂钴/碳催化剂在电催化氧还原领域有一定的应用前景。2.以乙酰丙酮铁和生物质琼脂为前躯体,通过简单的自我膨胀过程制备了一种新颖的泡沫状的碳化铁氮掺杂琼脂材料(标记为Fe/C-NA)。乙酰丙酮铁可以均匀的分散在琼脂中,避免了纳米粒子的团聚现象。这种方法制备的催化剂具有非常大的比表面积(1327.7 m2g-1),氮掺杂量可达到3.09%。其中典型催化剂泡沫状的网络结构使其导电性提高,能够促进离子和电子的传输,有利于Fe-C活性位点形成。在碱性溶液中,我们制备的代表性催化剂表现出优异的电催化氧还原性能,起始电位与商业Pt/C(20 wt%)相当,极限扩散电可以达到-5.34mA cm-2,略低于商业Pt/C的5.47 mA cm-2;典型催化剂显示出优异的抗甲醇性能,同时稳定性测试表明经过5000次循环之后极限扩散电流依然可以保持91.4%,ORR反应几乎全部按四电子过程进行。典型催化剂在酸性溶液中同样具有较好的氧还原催化性能、稳定性和抗甲醇性能。3.以二茂铁作为铁源,通过水热、高温热解的三步法,成功制备一维竹节状氮掺杂碳纳米管负载铁基纳米粒子(FexCyNz/N-CNT)材料。通过调控二茂铁和二氰二胺的比例及热解温度,得到代表性产物FexCyNz/N-CNT-1000材料。电化学测试结果表明,典型材料呈现优异的电催化氧还原性能,在碱性介质中,极限电流密度比商业Pt/C还要高0.54 mA cm-2、与商业Pt/C相比,表现出更加优异的长期稳定性及抗甲醇性能,其氧还原过程接近4电子转移过程。更有趣的是,通过吸波测试发现,当FexCyNz/N-CNT-1000的含量为12 wt%时,代表性产物与石蜡的混合物表现出最佳的吸波性能。因此,我们制备的FexCyNz/N-CNT-1000产物是一种高效的氧还原催化剂和电磁波吸收剂。这种新型的双功能纳米材料体系,可以为合理设计目标应用的多功能材料开辟一条新路。
[Abstract]:Fuel cell energy conversion technology as one of the most promising, with high energy efficiency, environmental friendly, more widely. It is a kind of new energy efficient use of hydrogen, in electrochemical reaction can directly convert chemical energy into electrical energy device. Because the cathodic oxygen reduction reaction (Oxygen Reduction Reaction, ORR) is very important in the fuel cell, the noble metal catalyst is still the best performance of the ORR cathode catalyst. However, because of these noble metal catalysts in nature reserves and scarce, the price is very expensive and the dynamic hysteresis effect, seriously restrict the commercialization of fuel cell applications. Therefore, the development and exploration of abundant resources, low price, high efficiency, non noble metal ORR catalyst durability is very important, has extraordinary practical significance and application prospect in current research. ORR cathode catalyst, carbon based catalyst of non noble metal for its high catalytic activity and stability and excellent anti methanol toxicity and other characteristics, has become extensive academic research topic. The research status of non noble metal carbon based catalyst and the basis of the work of our research group based on the use of carbon nanotubes, agar as the main carbon the source, through several different methods of hetero atom doped with transition metal carbon skeleton, a series of efficient transition metal carbon based ORR catalysts were prepared successfully. The main contents and results are as follows: 1. with carbon nanotubes, cobalt sulfamate, two nitrile two amine as raw materials by a simple ultrasonic dispersion method, solvent evaporation preparation of the precursor compound, and after high-temperature pyrolysis successfully prepared nitrogen, sulfur doped cobalt / carbon catalyst. By scanning electron microscopy, transmission electron microscopy, X ray diffraction, BET surface area measurement and so on The final products were characterized respectively, and test the ORR performance of the final product in alkaline and acidic solution. The electrochemical test results show that in alkaline solution, typical catalysts exhibit excellent ORR performance, the limiting diffusion current up to -5.43 mA cm-2, the electron transfer number close to 4, anti methanol toxicity and long-term stability is also very good. In addition electrocatalytic performance of typical catalyst, under acidic conditions are relatively good. This kind of mesoporous nano tubular nitrogen, sulfur doped cobalt / carbon reduction catalyst in electrocatalytic oxygen has certain application prospect of.2. in iron acetylacetonate and raw material agar as the precursor by simple self expansion process of preparation of iron carbide nitrogen a foamed material doped agar of the novel (labeled Fe/C-NA). Iron acetylacetonate can be uniformly dispersed in the agar and avoid the agglomeration of nanoparticles. The preparation method. The agent has a very large surface area (1327.7 m2g-1), nitrogen doping amount can reach 3.09%. in which the network structure of a typical catalyst foam to improve the conductivity, can promote the transport of ions and electrons, is conducive to the formation of the active site of Fe-C. In alkaline solution, we prepared a representative catalyst showed power excellent catalytic oxygen reduction performance, initial potential and commercial Pt/C (20 wt%), the limiting diffusion electricity can reach -5.34mA cm-2, slightly lower than the commercial Pt/C mA 5.47 cm-2; typical catalysts show excellent anti methanol performance at the same time, the stability test shows that after 5000 cycles, the limiting diffusion current can still maintain 91.4%, ORR almost all of the four electron reaction process. Typical catalysts both have better electrocatalytic performance for oxygen reduction in acid solution, stability and anti methanol performance of.3. with two ferrocene as iron source, through Water heat, three step pyrolysis, the successful preparation of one-dimensional doped nitrogen doped carbon nanotubes supported Fe nanoparticles (FexCyNz/N-CNT) materials. Through the regulation of two ferrocene and two cyano two amine proportion and pyrolysis temperature, get the representative product of FexCyNz/N-CNT-1000 materials. The electrochemical test results show that the typical material exhibits excellent electrocatalytic oxygen reduction the performance in alkaline medium, the limiting current density is 0.54 higher than that of the commercial Pt/C mA cm-2, compared with the commercial Pt/C, showed more excellent long-term stability and anti methanol performance, the oxygen reduction process nearly 4 electron transfer process. More interestingly, by absorbing test found that when the content of FexCyNz/N-CNT-1000 is 12 wt%, a mixture of representative products and paraffin showed the best absorbing performance. Therefore, we made FexCyNz/N-CNT-1000 product prepared is an efficient catalyst for oxygen reduction and electricity Magnetic absorber. This new dual function nanomaterial system can open up a new way for the rational design of multi-functional materials applied to the target.

【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TM911.4

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